The document summarizes John Schlee's 1957 study of the "upland deposits" of southern Maryland and presents an alternative hypothesis that these deposits originated from ejecta from the Chesapeake Bay crater. Schlee had analyzed the deposits and determined they could not have been formed through fluvial processes, but he was unaware of the crater's existence. The author notes issues with the accepted fluvial model and presents evidence from Schlee's data that the cobble sizes decrease with distance in a pattern suggestive of atmospheric sorting during ejection from an impact, with the direction of the crater at the origin point.
Evidence is given that the ejecta blanket of the 35.5-Myr-old Chesapeake Bay crater is still extant and covers ~5,000 km2 of the U.S. mid Atlantic Coastal Plain (Part 1 of 3)
This document discusses various geological processes that shape Earth's surface over long periods of time. It describes how stress and strain lead to folding and faulting in the crust. It also explains how volcanic activity, earthquakes, and plate tectonics result in mountain building and other surface features. Key points include how the principle of uniformity helps us understand slow, gradual changes versus sudden catastrophic events, and how different rock types respond to stress depending on temperature, pressure, and time.
1) Geologic time is measured in intervals of thousands, millions, or billions of years rather than using biblical ages.
2) James Ussher concluded in 1650 that God created Earth on October 22, 4004 BC, but Nicholas Steno initiated determining Earth's age scientifically in the late 1600s.
3) James Hutton developed the modern concept of geologic time and uniformitarianism, proposing that slow geologic processes seen today also operated in the past, implying a much older Earth than 6000 years.
Taylor proposed the concept of continental drift in 1908, hypothesizing that continents had shifted horizontally across Earth's surface over geological time. He suggested that the Arctic Sea was formed when Greenland and Siberia drifted apart, and that gaps between landmasses were filled by water to form oceans like the Atlantic and Indian Ocean. Taylor's continental drift theory was one of the first attempts to explain observations that seemed to support the idea of continental plate movements.
This document contains questions and answers related to Earth's interior structure and plate tectonics. It begins with category and point values for questions, then provides questions about Earth's layers, heat transfer mechanisms, continental drift evidence, plate tectonics forces, and plate boundary types. The questions cover topics like the inner core's composition, mantle sublayers, convection currents, Pangaea, sonar mapping of mid-ocean ridges, and mountain building at convergent boundaries.
The student collected samples near their home in Eagle Rock, Los Angeles. Samples included birds (peacocks and palm trees), which have been in the area for millions of years. The geological history of the Los Angeles Basin details how the area was submerged underwater 15 million years ago, and surrounding mountain shifts caused the crust to stretch and collapse, forming a basin filled with sediment over millions of years. However, the student was unable to find examples of geological principles or unconformities in the local area.
1. The document discusses sea-floor spreading, which is the process where new oceanic crust forms at mid-ocean ridges as tectonic plates move away from each other.
2. Evidence that supports sea-floor spreading includes magnetic stripe patterns in the ocean floor and samples from ocean crust that show it is younger near ridges and older further away.
3. Oceanic crust is basaltic rock that forms at ridges and is then recycled in subduction zones, making it generally younger than continental crust which does not undergo this recycling process.
The document discusses three types of plate boundaries:
1) Divergent boundaries, where plates pull apart and new crust is formed, examples include mid-ocean ridges and continental rift valleys.
2) Convergent boundaries, where plates push together, examples include oceanic-continental collisions which form volcanoes and trenches, and oceanic-oceanic collisions which form island arcs.
3) Transform boundaries, where plates slide horizontally past one another along transform faults.
Evidence is given that the ejecta blanket of the 35.5-Myr-old Chesapeake Bay crater is still extant and covers ~5,000 km2 of the U.S. mid Atlantic Coastal Plain (Part 1 of 3)
This document discusses various geological processes that shape Earth's surface over long periods of time. It describes how stress and strain lead to folding and faulting in the crust. It also explains how volcanic activity, earthquakes, and plate tectonics result in mountain building and other surface features. Key points include how the principle of uniformity helps us understand slow, gradual changes versus sudden catastrophic events, and how different rock types respond to stress depending on temperature, pressure, and time.
1) Geologic time is measured in intervals of thousands, millions, or billions of years rather than using biblical ages.
2) James Ussher concluded in 1650 that God created Earth on October 22, 4004 BC, but Nicholas Steno initiated determining Earth's age scientifically in the late 1600s.
3) James Hutton developed the modern concept of geologic time and uniformitarianism, proposing that slow geologic processes seen today also operated in the past, implying a much older Earth than 6000 years.
Taylor proposed the concept of continental drift in 1908, hypothesizing that continents had shifted horizontally across Earth's surface over geological time. He suggested that the Arctic Sea was formed when Greenland and Siberia drifted apart, and that gaps between landmasses were filled by water to form oceans like the Atlantic and Indian Ocean. Taylor's continental drift theory was one of the first attempts to explain observations that seemed to support the idea of continental plate movements.
This document contains questions and answers related to Earth's interior structure and plate tectonics. It begins with category and point values for questions, then provides questions about Earth's layers, heat transfer mechanisms, continental drift evidence, plate tectonics forces, and plate boundary types. The questions cover topics like the inner core's composition, mantle sublayers, convection currents, Pangaea, sonar mapping of mid-ocean ridges, and mountain building at convergent boundaries.
The student collected samples near their home in Eagle Rock, Los Angeles. Samples included birds (peacocks and palm trees), which have been in the area for millions of years. The geological history of the Los Angeles Basin details how the area was submerged underwater 15 million years ago, and surrounding mountain shifts caused the crust to stretch and collapse, forming a basin filled with sediment over millions of years. However, the student was unable to find examples of geological principles or unconformities in the local area.
1. The document discusses sea-floor spreading, which is the process where new oceanic crust forms at mid-ocean ridges as tectonic plates move away from each other.
2. Evidence that supports sea-floor spreading includes magnetic stripe patterns in the ocean floor and samples from ocean crust that show it is younger near ridges and older further away.
3. Oceanic crust is basaltic rock that forms at ridges and is then recycled in subduction zones, making it generally younger than continental crust which does not undergo this recycling process.
The document discusses three types of plate boundaries:
1) Divergent boundaries, where plates pull apart and new crust is formed, examples include mid-ocean ridges and continental rift valleys.
2) Convergent boundaries, where plates push together, examples include oceanic-continental collisions which form volcanoes and trenches, and oceanic-oceanic collisions which form island arcs.
3) Transform boundaries, where plates slide horizontally past one another along transform faults.
The document summarizes key aspects of plate tectonics theory. There are 12 major tectonic plates and several minor plates that make up the Earth's surface. The plates move over time via processes like convection currents in the mantle. Plate boundaries are marked by tectonic activity and different types of crust exist, with oceanic crust being thinner and younger than continental crust.
Sara Arif - EDSC 304 - Teacher Lecture & Guided Notes - Plate Tectonics and E...sararif16
The document discusses the theory of plate tectonics and how it explains the formation and movement of continents over time. Around 250 million years ago, all the continents were joined together in a supercontinent called Pangea. Over millions of years, Pangea broke apart and the continents drifted to their current locations, carried by tectonic plates in the Earth's mantle. New crust is formed at mid-ocean ridges as plates move apart, while older crust is recycled at deep ocean trenches as plates converge. The movement of tectonic plates causes earthquakes, particularly at plate boundaries where plates collide, slide past each other, or move apart.
The document summarizes research on the concentric crater located in Humboldt on the Moon. It finds that the concentric crater is typical in size and ratio of inner to outer ring diameters compared to other known concentric craters. Spectral analysis indicates the interior of the concentric crater is composed of highland material, supporting the hypothesis that it formed through igneous intrusion rather than volcanic extrusion. The proximity of two younger, non-concentric craters of similar size suggests conditions for concentric crater formation no longer existed at the time of their impacts. Together, this provides evidence that the concentric crater in Humboldt formed through igneous intrusion rather than volcanic activity.
Continental drift &and sea floor spreadingMd Asif Hasan
The document discusses the theories of continental drift, seafloor spreading, and plate tectonics. It provides details on the original proponent of continental drift theory, Alfred Wegener, in 1915. It also outlines various geological, climatic, and biological evidence that supports continental drift. The document then discusses the sea floor spreading theory proposed by Harry Hess in the 1960s, which helped explain continental drift. It notes evidence that the ocean floor becomes progressively younger near mid-ocean ridges. Finally, it describes how the theories of continental drift and sea floor spreading were combined into the comprehensive theory of plate tectonics.
The document discusses plate tectonics, including that the Earth's crust is broken into plates that move atop the mantle. There are two types of plates - oceanic and continental. Plates interact at three types of boundaries: divergent boundaries where plates separate and new seafloor is created, convergent boundaries where plates collide resulting in subduction zones or mountain building, and transform boundaries where plates slide past one another causing earthquakes. Convection currents in the underlying mantle are cited as the cause of plate tectonic movement.
The document discusses the theory of plate tectonics. [1] The Earth's crust and upper mantle are broken into sections called plates that move around on top of the mantle. [2] The lithosphere comprises the crust and part of the upper mantle and "floats" on the asthenosphere, which is the plastic layer below. [3] There are two types of plates - ocean plates below oceans and continental plates below continents.
The theory of plate tectonics describes how the Earth's crust is broken into plates that move around on the mantle. The lithosphere consists of the crust and rigid upper mantle, which floats on the asthenosphere, a plastic layer that allows the plates to move. There are two types of plates - oceanic and continental. Plates interact at boundaries, where they can move apart, collide together, or slide past one another, causing earthquakes. Convection currents in the mantle provide the driving force for plate tectonics as hot rock rises and cools, sinking and repeating the cycle.
This document discusses plate tectonics and the evidence that supports the theory. It describes how Alfred Wegener first proposed continental drift in 1912 and how the theory was rejected until the 1950s. The discovery of mid-ocean ridges provided evidence that the ocean floors were spreading and pushing the continents apart. Rocks and fossils found on separated continents matched and indicated they were once joined together in a supercontinent called Pangaea. The theory of plate tectonics emerged, linking continental drift and seafloor spreading to explain how the Earth's crust has evolved over time through the movement of tectonic plates.
The document discusses relative dating techniques used by geologists to determine the ages of rock layers. It explains that Nicolaus Steno established the concept of relative dating by observing that sedimentary rock layers are ordered chronologically. The two main laws of relative dating are the law of original horizontality and the law of superposition. Unconformities in the rock record, caused by erosion, and the cross-cutting relationships of intrusions and extrusions also provide clues about relative ages. Fossils can be used to relatively date rock layers if they are index fossils that have been absolutely dated elsewhere.
The Moon formed about 4.45 billion years ago from debris ejected when a large object collided with Earth. It has since been shaped primarily by relentless bombardment from impacts. Exploration of the Moon began with telescopic observations in the 1600s and recent robotic missions have revealed much about its geology and origins, but many questions remain unanswered, motivating continued exploration including future human missions.
Evidence is given that the ejecta blanket of the 35.5-Myr-old Chesapeake Bay Crater is still extant and covers ~5,000 km2 of the U.S. mid Atlantic Coastal plain
The earliest material found in the Solar System is dated to 4.5672±0.0006 by] therefore, it is inferred that the Earth must have been formed by accretion around this time. By 4.54±0.04 by the primordial Earth had formed. The formation and evolution of the Solar System bodies occurred in tandem with the Sun. In theory a solar nebula partitions a volume out of a molecular cloud by gravitational collapse, which begins to spin and flatten into a circumstellar disk, and then the planets
grow out of that in tandem with the star. A nebula contains gas, ice grains and dust
The document discusses several principles of relative dating that allow geologists to determine the sequence of rock layers based on their order of formation. The Law of Superposition states that lower layers are older than those above. Index fossils found in rock layers can also be used to relatively date the layers, as some fossil types were present only during short, distinct periods of geologic time. Unconformities in the rock record indicate periods where deposition stopped and erosion occurred.
This document discusses the geologic time scale and the history of life on Earth. It describes how paleontologists divide Earth's history into major eras including the Precambrian, Paleozoic, Mesozoic, and Cenozoic eras. Each era is characterized by the dominant life forms present in the rocks and fossils from that time period. The document also discusses concepts like mass extinctions, absolute dating using radioactive decay, and half-life.
This PowerPoint is one small part of the Geology Topics unit from www.sciencepowerpoint.com. This unit consists of a five part 6000+ slide PowerPoint roadmap, 14 page bundled homework package, modified homework, detailed answer keys, 12 pages of unit notes for students who may require assistance, follow along worksheets, and many review games. The homework and lesson notes chronologically follow the PowerPoint slideshow. The answer keys and unit notes are great for support professionals. The activities and discussion questions in the slideshow are meaningful. The PowerPoint includes built-in instructions, visuals, and review questions. Also included are critical class notes (color coded red), project ideas, video links, and review games. This unit also includes four PowerPoint review games (110+ slides each with Answers), 38+ video links, lab handouts, activity sheets, rubrics, materials list, templates, guides, 6 PowerPoint review Game, and much more. Also included is a 190 slide first day of school PowerPoint presentation.
Areas of Focus within The Geology Topics Unit: -Plate Tectonics, Evidence for Plate Tectonics, Pangea, Energy Waves, Layers of the Earth, Heat Transfer, Types of Crust, Plate Boundaries, Hot Spots, Volcanoes, Positives and Negatives of Volcanoes, Types of Volcanoes, Parts of a Volcano, Magma, Types of Lava, Viscosity, Earthquakes, Faults, Folds, Seismograph, Richter Scale, Seismograph, Tsunami's, Rocks, Minerals, Crystals, Uses of Minerals, Types of Crystals, Physical Properties of Minerals, Rock Cycle, Common Igneous Rocks, Common Sedimentary Rocks, Common Metamorphic Rocks.
This unit aligns with the Next Generation Science Standards and with Common Core Standards for ELA and Literacy for Science and Technical Subjects. See preview for more information
If you have any questions please feel free to contact me. Thanks again and best wishes. Sincerely, Ryan Murphy M.Ed www.sciencepowerpoint@gmail.com
The document provides a summary of the geology tour given by Mike Stoever of the Washington D.C. area. It discusses the major geological processes that led to the formation of the area, including plate tectonics, erosion and deposition, a meteorite impact, and sea level changes. It then describes the four main geological provinces that make up the D.C. area, and highlights several important geological features, such as the Fall Line, Teddy Roosevelt Island, and Great Falls Park.
Evidence is presented that the ejecta blanket of the 35.5-Myr-old Chesapeake Bay crater is still extant and covers ~5,000 km2 of the U.S. mid Atlantic Coastal Plain. (Part 3 of 3)
Ussher calculated that the Earth was created on October 23, 4004 BC based on biblical chronology. He also dated other biblical events like Adam and Eve being expelled from the Garden of Eden on Monday, October 10, 4004 BC and Noah's ark landing on Mount Ararat on Wednesday, May 5, 2348 BC. The document then discusses various dating techniques used in geology like stratigraphy, fluorine analysis, pollen analysis, and radioactive carbon dating to determine the absolute and relative age of geological features and fossils. It provides examples of evidence for past ice ages like erratic boulders, moraines, U-shaped valleys, and drowned river valleys.
The document discusses plate tectonics and the evidence supporting continental drift. It describes how Wegener first proposed the hypothesis of continental drift in 1912 based on observations that the continents seemed to fit together. The document outlines several pieces of evidence that supported Wegener's hypothesis, including matching coastlines, shared fossil distributions, and geological and climatic similarities between separated continents. It then describes how the theory of seafloor spreading provided further evidence when studies in the 1940s and 1950s showed the ocean floor was younger than the continents and spreading occurred at mid-ocean ridges. Paleomagnetic data from the seafloor also supported seafloor spreading and continental drift. Today the theory of plate tectonics unifies
its about earth quake
Some plates have continents; some don't. All are in motion. Question: What evidence is there for these plate boundaries? Tectonic Plates ...
The Grand Canyon formed through a combination of uplift of the Colorado Plateau and incision by the Colorado River. Two main theories for its formation are the Headward Erosion Theory, which involves capture of an ancestral river by upstream erosion, and the Spillover Theory, where a blocked river spilled over the plateau. Both theories have issues, and the exact timeline and mechanisms are still debated. Uplift starting around 80 million years ago drove stream capture and erosion that excavated the canyon over millions of years.
The document summarizes key aspects of plate tectonics theory. There are 12 major tectonic plates and several minor plates that make up the Earth's surface. The plates move over time via processes like convection currents in the mantle. Plate boundaries are marked by tectonic activity and different types of crust exist, with oceanic crust being thinner and younger than continental crust.
Sara Arif - EDSC 304 - Teacher Lecture & Guided Notes - Plate Tectonics and E...sararif16
The document discusses the theory of plate tectonics and how it explains the formation and movement of continents over time. Around 250 million years ago, all the continents were joined together in a supercontinent called Pangea. Over millions of years, Pangea broke apart and the continents drifted to their current locations, carried by tectonic plates in the Earth's mantle. New crust is formed at mid-ocean ridges as plates move apart, while older crust is recycled at deep ocean trenches as plates converge. The movement of tectonic plates causes earthquakes, particularly at plate boundaries where plates collide, slide past each other, or move apart.
The document summarizes research on the concentric crater located in Humboldt on the Moon. It finds that the concentric crater is typical in size and ratio of inner to outer ring diameters compared to other known concentric craters. Spectral analysis indicates the interior of the concentric crater is composed of highland material, supporting the hypothesis that it formed through igneous intrusion rather than volcanic extrusion. The proximity of two younger, non-concentric craters of similar size suggests conditions for concentric crater formation no longer existed at the time of their impacts. Together, this provides evidence that the concentric crater in Humboldt formed through igneous intrusion rather than volcanic activity.
Continental drift &and sea floor spreadingMd Asif Hasan
The document discusses the theories of continental drift, seafloor spreading, and plate tectonics. It provides details on the original proponent of continental drift theory, Alfred Wegener, in 1915. It also outlines various geological, climatic, and biological evidence that supports continental drift. The document then discusses the sea floor spreading theory proposed by Harry Hess in the 1960s, which helped explain continental drift. It notes evidence that the ocean floor becomes progressively younger near mid-ocean ridges. Finally, it describes how the theories of continental drift and sea floor spreading were combined into the comprehensive theory of plate tectonics.
The document discusses plate tectonics, including that the Earth's crust is broken into plates that move atop the mantle. There are two types of plates - oceanic and continental. Plates interact at three types of boundaries: divergent boundaries where plates separate and new seafloor is created, convergent boundaries where plates collide resulting in subduction zones or mountain building, and transform boundaries where plates slide past one another causing earthquakes. Convection currents in the underlying mantle are cited as the cause of plate tectonic movement.
The document discusses the theory of plate tectonics. [1] The Earth's crust and upper mantle are broken into sections called plates that move around on top of the mantle. [2] The lithosphere comprises the crust and part of the upper mantle and "floats" on the asthenosphere, which is the plastic layer below. [3] There are two types of plates - ocean plates below oceans and continental plates below continents.
The theory of plate tectonics describes how the Earth's crust is broken into plates that move around on the mantle. The lithosphere consists of the crust and rigid upper mantle, which floats on the asthenosphere, a plastic layer that allows the plates to move. There are two types of plates - oceanic and continental. Plates interact at boundaries, where they can move apart, collide together, or slide past one another, causing earthquakes. Convection currents in the mantle provide the driving force for plate tectonics as hot rock rises and cools, sinking and repeating the cycle.
This document discusses plate tectonics and the evidence that supports the theory. It describes how Alfred Wegener first proposed continental drift in 1912 and how the theory was rejected until the 1950s. The discovery of mid-ocean ridges provided evidence that the ocean floors were spreading and pushing the continents apart. Rocks and fossils found on separated continents matched and indicated they were once joined together in a supercontinent called Pangaea. The theory of plate tectonics emerged, linking continental drift and seafloor spreading to explain how the Earth's crust has evolved over time through the movement of tectonic plates.
The document discusses relative dating techniques used by geologists to determine the ages of rock layers. It explains that Nicolaus Steno established the concept of relative dating by observing that sedimentary rock layers are ordered chronologically. The two main laws of relative dating are the law of original horizontality and the law of superposition. Unconformities in the rock record, caused by erosion, and the cross-cutting relationships of intrusions and extrusions also provide clues about relative ages. Fossils can be used to relatively date rock layers if they are index fossils that have been absolutely dated elsewhere.
The Moon formed about 4.45 billion years ago from debris ejected when a large object collided with Earth. It has since been shaped primarily by relentless bombardment from impacts. Exploration of the Moon began with telescopic observations in the 1600s and recent robotic missions have revealed much about its geology and origins, but many questions remain unanswered, motivating continued exploration including future human missions.
Evidence is given that the ejecta blanket of the 35.5-Myr-old Chesapeake Bay Crater is still extant and covers ~5,000 km2 of the U.S. mid Atlantic Coastal plain
The earliest material found in the Solar System is dated to 4.5672±0.0006 by] therefore, it is inferred that the Earth must have been formed by accretion around this time. By 4.54±0.04 by the primordial Earth had formed. The formation and evolution of the Solar System bodies occurred in tandem with the Sun. In theory a solar nebula partitions a volume out of a molecular cloud by gravitational collapse, which begins to spin and flatten into a circumstellar disk, and then the planets
grow out of that in tandem with the star. A nebula contains gas, ice grains and dust
The document discusses several principles of relative dating that allow geologists to determine the sequence of rock layers based on their order of formation. The Law of Superposition states that lower layers are older than those above. Index fossils found in rock layers can also be used to relatively date the layers, as some fossil types were present only during short, distinct periods of geologic time. Unconformities in the rock record indicate periods where deposition stopped and erosion occurred.
This document discusses the geologic time scale and the history of life on Earth. It describes how paleontologists divide Earth's history into major eras including the Precambrian, Paleozoic, Mesozoic, and Cenozoic eras. Each era is characterized by the dominant life forms present in the rocks and fossils from that time period. The document also discusses concepts like mass extinctions, absolute dating using radioactive decay, and half-life.
This PowerPoint is one small part of the Geology Topics unit from www.sciencepowerpoint.com. This unit consists of a five part 6000+ slide PowerPoint roadmap, 14 page bundled homework package, modified homework, detailed answer keys, 12 pages of unit notes for students who may require assistance, follow along worksheets, and many review games. The homework and lesson notes chronologically follow the PowerPoint slideshow. The answer keys and unit notes are great for support professionals. The activities and discussion questions in the slideshow are meaningful. The PowerPoint includes built-in instructions, visuals, and review questions. Also included are critical class notes (color coded red), project ideas, video links, and review games. This unit also includes four PowerPoint review games (110+ slides each with Answers), 38+ video links, lab handouts, activity sheets, rubrics, materials list, templates, guides, 6 PowerPoint review Game, and much more. Also included is a 190 slide first day of school PowerPoint presentation.
Areas of Focus within The Geology Topics Unit: -Plate Tectonics, Evidence for Plate Tectonics, Pangea, Energy Waves, Layers of the Earth, Heat Transfer, Types of Crust, Plate Boundaries, Hot Spots, Volcanoes, Positives and Negatives of Volcanoes, Types of Volcanoes, Parts of a Volcano, Magma, Types of Lava, Viscosity, Earthquakes, Faults, Folds, Seismograph, Richter Scale, Seismograph, Tsunami's, Rocks, Minerals, Crystals, Uses of Minerals, Types of Crystals, Physical Properties of Minerals, Rock Cycle, Common Igneous Rocks, Common Sedimentary Rocks, Common Metamorphic Rocks.
This unit aligns with the Next Generation Science Standards and with Common Core Standards for ELA and Literacy for Science and Technical Subjects. See preview for more information
If you have any questions please feel free to contact me. Thanks again and best wishes. Sincerely, Ryan Murphy M.Ed www.sciencepowerpoint@gmail.com
The document provides a summary of the geology tour given by Mike Stoever of the Washington D.C. area. It discusses the major geological processes that led to the formation of the area, including plate tectonics, erosion and deposition, a meteorite impact, and sea level changes. It then describes the four main geological provinces that make up the D.C. area, and highlights several important geological features, such as the Fall Line, Teddy Roosevelt Island, and Great Falls Park.
Evidence is presented that the ejecta blanket of the 35.5-Myr-old Chesapeake Bay crater is still extant and covers ~5,000 km2 of the U.S. mid Atlantic Coastal Plain. (Part 3 of 3)
Ussher calculated that the Earth was created on October 23, 4004 BC based on biblical chronology. He also dated other biblical events like Adam and Eve being expelled from the Garden of Eden on Monday, October 10, 4004 BC and Noah's ark landing on Mount Ararat on Wednesday, May 5, 2348 BC. The document then discusses various dating techniques used in geology like stratigraphy, fluorine analysis, pollen analysis, and radioactive carbon dating to determine the absolute and relative age of geological features and fossils. It provides examples of evidence for past ice ages like erratic boulders, moraines, U-shaped valleys, and drowned river valleys.
The document discusses plate tectonics and the evidence supporting continental drift. It describes how Wegener first proposed the hypothesis of continental drift in 1912 based on observations that the continents seemed to fit together. The document outlines several pieces of evidence that supported Wegener's hypothesis, including matching coastlines, shared fossil distributions, and geological and climatic similarities between separated continents. It then describes how the theory of seafloor spreading provided further evidence when studies in the 1940s and 1950s showed the ocean floor was younger than the continents and spreading occurred at mid-ocean ridges. Paleomagnetic data from the seafloor also supported seafloor spreading and continental drift. Today the theory of plate tectonics unifies
its about earth quake
Some plates have continents; some don't. All are in motion. Question: What evidence is there for these plate boundaries? Tectonic Plates ...
The Grand Canyon formed through a combination of uplift of the Colorado Plateau and incision by the Colorado River. Two main theories for its formation are the Headward Erosion Theory, which involves capture of an ancestral river by upstream erosion, and the Spillover Theory, where a blocked river spilled over the plateau. Both theories have issues, and the exact timeline and mechanisms are still debated. Uplift starting around 80 million years ago drove stream capture and erosion that excavated the canyon over millions of years.
The document summarizes the key principles of plate tectonics. It describes how the lithosphere is composed of rigid tectonic plates that move across the asthenosphere. The three main types of plate boundaries are divergent boundaries where plates move apart, convergent boundaries where they move together, and transform boundaries where they slide past each other. Evidence that supports plate tectonics includes the distribution and age of ocean floor, magnetic patterns in rocks, paleomagnetic data, polar wander curves, and geological features correlated across continents.
Plate Tectonics
Chapter 19
Plate TectonicsPlate tectonics - Earth’s surface composed thick plates that moveIntense geologic activity is concentrated at plate boundariesCombination of continental drift and seafloor spreading hypotheses proposed in late 1960s
Review: Three Types of Plate Boundaries
But how do we
know that plates
move at all ?
Transform Convergent Divergent
(strike-slip) (subduction) (spreading)
Early Case for Continental DriftPuzzle-piece fit of coastlines of Africa and South America has long been known
In early 1900s, Alfred Wegner noted South America, Africa, India, Antarctica, and Australia have almost identical rocks and fossils
Early Case for Continental DriftGlossopteris (plant), Lystrosaurus and Cynognathus (animals) fossils found on all five continents Mesosaurus (reptile) fossils found in Brazil and South Africa only
Glaciers Most of the Earth's ice is found in Antarctic continental glacier. Where are some other continental glaciers ?
FIGURE 10.5 Iceberg calving at Wrangell-St. Elias National Park, Alaska. Calving occurs when huge blocks of ice break off at the edge of a glacier that has moved to a shoreline. [Tom Bean.]
Glacial striations on a rock from stones grinding at the base of a heavy ice sheet leave these shiny linear marks on the bedrock below.
FIGURE 10.18 Glacial striations on bedrock in Glacier Bay National Park, Alaska. Striations are evidence of the direction of ice movement and are especially important clues for reconstructing the movement of continental glaciers. [Carr Clifton.]
Glacial Characteristics Glaciers flow downhill as a solid mass that creates channels, and walls made of ground up rock debris known as a merraine.
Erosional LandscapesErosional landforms produced by valley glaciers include: U-shaped valleys Hanging valleysSmaller tributary glacial valleys left stranded above more quickly eroded central valleys
Early Case for Continental DriftWegner reassembled continents into the supercontinent Pangaea
Late Paleozoic glaciation patterns on southern continents best explained by their reconstruction into (Pangaea) Gondwanaland
Early Case for Continental DriftCoal beds of North America and Europe indicate Laurasia super continent
Continental Drift hypothesis initially rejected Wegener could not come up with viable driving force continents should not be able to “plow through” sea floor rocks
The Earth's Magnetic Field
Can Give Us Clues
Paleomagnetism and Continental Drift RevivedStudies of rock magnetism allowed determination of magnetic pole locations (close to geographic poles) Paleomagnetism uses mineral magnetic alignment and dip angle to determine the distance to the magnetic pole when rocks formedSteeper dip angles indicate rocks formed closer .
The document provides an overview of several geological models that were used in the early 20th century to understand global geological features, including continental drift. It discusses the theory of contractionism, which proposed that continents separated as the Earth cooled and shrank. It also discusses permanentenism, which argued that continents have always been in largely the same positions. The land-bridge hypothesis suggested that land bridges once connected continents to explain terrestrial fossil distributions. The document examines problems with each of these early models and how they helped address questions about matching fossil distributions across continents.
The document summarizes plate tectonics, providing details on:
1) The structure of the Earth's core and mantle, and how convection currents cause plate movements.
2) Evidence for plate tectonics including seafloor spreading and magnetic reversals in ocean crust.
3) The three types of plate boundaries and associated geological features like ocean trenches and volcanic activity.
This document provides information about plate tectonics and related geological concepts. It begins with an overview of plate tectonics theory, including the three main types of plate boundaries (transform, convergent, and divergent). It then discusses early evidence that supported continental drift, including matching coastlines and shared fossil distributions. Additional sections cover paleomagnetism data, seafloor spreading evidence, characteristics of different plate boundary types, and potential driving forces of plate tectonics like mantle convection. The document concludes by discussing mountain building at plate boundaries and ways plate tectonics may operate on other celestial bodies.
The document discusses the structure and composition of the Earth. It describes the lithosphere as the solid outermost part made up of tectonic plates that move over time. The layers within the lithosphere are described based on their composition of crust, mantle and core, as well as their physical properties. Evidence for plate tectonics and continental drift is provided.
Plate tectonics describes the large-scale motions of Earth's major tectonic plates. Evidence for plate tectonics includes matching rock formations and fossil patterns found on separated continents, as well as evidence of past climate changes in rock strata. The theory was confirmed in the 1960s with discoveries about seafloor spreading and paleomagnetism recording magnetic reversals in oceanic crust. Plate boundaries such as mid-ocean ridges and trenches demonstrate the movement of plates via convection currents in the mantle.
2013 updated plate tectonics new one use this oneharvey09
The document summarizes plate tectonics and the development of the theory. It describes how early scientists like Wegener proposed continental drift but lacked evidence. Later, mapping of the ocean floor revealed patterns of magnetic stripes and rock ages indicating the seafloor spreads from mid-ocean ridges. This led scientists in the 1960s to develop the modern theory of plate tectonics, which proposes that Earth's crust is divided into plates that move due to convection currents in the mantle.
Orchard Beach, Pelham BayVirtual Field TripWhere are.docxhopeaustin33688
Orchard Beach, Pelham Bay
Virtual Field Trip
Where are we going?
• Orchard Beach at Pelham Bay
Park in Bronx, Northernmost
borough of NYC
• From the parking lot, walk on
the gravel path past tennis
courts toward the sound, then
walk NE along the beach to Twin
Islands
• This 10-20 minute walk will
include several stops
What are we going to see?
• Hartland formation: exotic terrane
(islands off the coast of Africa) that
collided with North America ~440 ma
• Devonian intrusions into the Cambro-
Ordovician rocks
• Evidence of glaciation (Wisconsin ice
sheet, 1000 ft thick in this part of NY, ~11
ka -80 ka)
• Sediments that were metamorphosed
during Taconic and Acadian orogenies
• Quartz-feldspar gneiss, biotite-sillimanite
schist, amphibolite
• Glacial till, glacial erratics, striations,
outwash plain, terminal moraine in the
distance
Map of NYC geology – US geological Survey
Tectonic evolution of the east coast:
• Follow along with this cartoon version of the
area’s tectonic history in your handout
• Overview:
• Grenville Orogeny completed the assembly of
Rodinia, ~1.5-1 ba
• Post-Grenville rifting created Iapetus ocean
• Iapetus ocean started closing
• Three pulses of Appalachian mountain building,
Taconian, Acadian, and Alleghanian orogenies,
close Iapetus Ocean
• Pangea breaks up in the Mesozoic, rifting creates
Atlantic ocean
• In this field trip we have glimpses into two of
the three pulses of Appalachian mountain-
building during early stages of Iapetan
closure: the Taconic Orogeny (Cambro-
Ordovician), and the Acadian Orogeny (late
Devonian)
Adapted from Earth: Portrait of a Planet by Steve
Marshak
Glaciation and 1st stop
• The top stratigraphic layers are much
younger than the tectonic events
described in the previous slide
• Ice age in the Pleistocene shaped
landscape, modified drainage, and eroded
strata
• Last advance of ice: Wisconsin stage of
the Laurentide ice sheet
• Terminal moraine at the edge of the ice
sheet creates Long Island
• Long Island Sound was a glacial lake; as
climate warmed and sea level rose, the
outwash lake became an estuary then a
sound; tall points of the moraine are now
islands
2nd stop: Hartland formation
• Hartland formation: exotic terrane
(islands off the coast of Africa) that
collided with North America ~440 ma
• Sediments that were metamorphosed
during two of the three pulses of
Appalachian mountain building:
Taconic and Acadian orogenies (check
tectonic evolution cartoon in your
handout)
• Quartz-feldspar gneiss, biotite-
sillimanite schist, amphibolite
• Follow the links; hope you can hear
me over the wind!
• https://youtu.be/aXcqGEgAH2k
• Severe deformation
• Partial melting of the schists and
gneiss produced abundant quartz-
feldspar leucosomes
• Leucosomes: lenticular shape, coarse-
grained, variable thickness, high-grade
metamorphism product
• Garnets: metamorphic index mineral
• https://youtu.be/j8YZUQW.
Orchard Beach, Pelham BayVirtual Field TripWhere arelianaalbee2qly
Orchard Beach, Pelham Bay
Virtual Field Trip
Where are we going?
• Orchard Beach at Pelham Bay
Park in Bronx, Northernmost
borough of NYC
• From the parking lot, walk on
the gravel path past tennis
courts toward the sound, then
walk NE along the beach to Twin
Islands
• This 10-20 minute walk will
include several stops
What are we going to see?
• Hartland formation: exotic terrane
(islands off the coast of Africa) that
collided with North America ~440 ma
• Devonian intrusions into the Cambro-
Ordovician rocks
• Evidence of glaciation (Wisconsin ice
sheet, 1000 ft thick in this part of NY, ~11
ka -80 ka)
• Sediments that were metamorphosed
during Taconic and Acadian orogenies
• Quartz-feldspar gneiss, biotite-sillimanite
schist, amphibolite
• Glacial till, glacial erratics, striations,
outwash plain, terminal moraine in the
distance
Map of NYC geology – US geological Survey
Tectonic evolution of the east coast:
• Follow along with this cartoon version of the
area’s tectonic history in your handout
• Overview:
• Grenville Orogeny completed the assembly of
Rodinia, ~1.5-1 ba
• Post-Grenville rifting created Iapetus ocean
• Iapetus ocean started closing
• Three pulses of Appalachian mountain building,
Taconian, Acadian, and Alleghanian orogenies,
close Iapetus Ocean
• Pangea breaks up in the Mesozoic, rifting creates
Atlantic ocean
• In this field trip we have glimpses into two of
the three pulses of Appalachian mountain-
building during early stages of Iapetan
closure: the Taconic Orogeny (Cambro-
Ordovician), and the Acadian Orogeny (late
Devonian)
Adapted from Earth: Portrait of a Planet by Steve
Marshak
Glaciation and 1st stop
• The top stratigraphic layers are much
younger than the tectonic events
described in the previous slide
• Ice age in the Pleistocene shaped
landscape, modified drainage, and eroded
strata
• Last advance of ice: Wisconsin stage of
the Laurentide ice sheet
• Terminal moraine at the edge of the ice
sheet creates Long Island
• Long Island Sound was a glacial lake; as
climate warmed and sea level rose, the
outwash lake became an estuary then a
sound; tall points of the moraine are now
islands
2nd stop: Hartland formation
• Hartland formation: exotic terrane
(islands off the coast of Africa) that
collided with North America ~440 ma
• Sediments that were metamorphosed
during two of the three pulses of
Appalachian mountain building:
Taconic and Acadian orogenies (check
tectonic evolution cartoon in your
handout)
• Quartz-feldspar gneiss, biotite-
sillimanite schist, amphibolite
• Follow the links; hope you can hear
me over the wind!
• https://youtu.be/aXcqGEgAH2k
• Severe deformation
• Partial melting of the schists and
gneiss produced abundant quartz-
feldspar leucosomes
• Leucosomes: lenticular shape, coarse-
grained, variable thickness, high-grade
metamorphism product
• Garnets: metamorphic index mineral
• https://youtu.be/j8YZUQW ...
Orchard Beach, Pelham BayVirtual Field TripWhere are.docxjacksnathalie
Orchard Beach, Pelham Bay
Virtual Field Trip
Where are we going?
• Orchard Beach at Pelham Bay
Park in Bronx, Northernmost
borough of NYC
• From the parking lot, walk on
the gravel path past tennis
courts toward the sound, then
walk NE along the beach to Twin
Islands
• This 10-20 minute walk will
include several stops
What are we going to see?
• Hartland formation: exotic terrane
(islands off the coast of Africa) that
collided with North America ~440 ma
• Devonian intrusions into the Cambro-
Ordovician rocks
• Evidence of glaciation (Wisconsin ice
sheet, 1000 ft thick in this part of NY, ~11
ka -80 ka)
• Sediments that were metamorphosed
during Taconic and Acadian orogenies
• Quartz-feldspar gneiss, biotite-sillimanite
schist, amphibolite
• Glacial till, glacial erratics, striations,
outwash plain, terminal moraine in the
distance
Map of NYC geology – US geological Survey
Tectonic evolution of the east coast:
• Follow along with this cartoon version of the
area’s tectonic history in your handout
• Overview:
• Grenville Orogeny completed the assembly of
Rodinia, ~1.5-1 ba
• Post-Grenville rifting created Iapetus ocean
• Iapetus ocean started closing
• Three pulses of Appalachian mountain building,
Taconian, Acadian, and Alleghanian orogenies,
close Iapetus Ocean
• Pangea breaks up in the Mesozoic, rifting creates
Atlantic ocean
• In this field trip we have glimpses into two of
the three pulses of Appalachian mountain-
building during early stages of Iapetan
closure: the Taconic Orogeny (Cambro-
Ordovician), and the Acadian Orogeny (late
Devonian)
Adapted from Earth: Portrait of a Planet by Steve
Marshak
Glaciation and 1st stop
• The top stratigraphic layers are much
younger than the tectonic events
described in the previous slide
• Ice age in the Pleistocene shaped
landscape, modified drainage, and eroded
strata
• Last advance of ice: Wisconsin stage of
the Laurentide ice sheet
• Terminal moraine at the edge of the ice
sheet creates Long Island
• Long Island Sound was a glacial lake; as
climate warmed and sea level rose, the
outwash lake became an estuary then a
sound; tall points of the moraine are now
islands
2nd stop: Hartland formation
• Hartland formation: exotic terrane
(islands off the coast of Africa) that
collided with North America ~440 ma
• Sediments that were metamorphosed
during two of the three pulses of
Appalachian mountain building:
Taconic and Acadian orogenies (check
tectonic evolution cartoon in your
handout)
• Quartz-feldspar gneiss, biotite-
sillimanite schist, amphibolite
• Follow the links; hope you can hear
me over the wind!
• https://youtu.be/aXcqGEgAH2k
• Severe deformation
• Partial melting of the schists and
gneiss produced abundant quartz-
feldspar leucosomes
• Leucosomes: lenticular shape, coarse-
grained, variable thickness, high-grade
metamorphism product
• Garnets: metamorphic index mineral
• https://youtu.be/j8YZUQW.
The document provides an overview of the structure and composition of the Earth's layers, including the crust, mantle, and core. It then discusses plate tectonics and evidence that supports the theory of continental drift, such as matching geological formations and fossil distributions between continents before they drifted apart. The development of the modern theory of plate tectonics to explain continental movement is also outlined.
Hawaii's Most Active Volcano: Here's The Latest On Kilauea's Eruption
The Kilauea volcano is located in the southeastern part of the Big Island of Hawaii.
Believe it or not, Kilauea has been erupting continuously since 1983, with only occasional pauses of quiet activity. This particular "episode" of the eruption began in the late afternoon of May 3, in a part of Leilani Estates, a subdivision near the town of Pahoa.
Officials said there is no way to predict how long the eruption will continue or what shape it will take. This eruption could be finished or could go on for a long time.
Kilauea is one of the most active and well-monitored volcanoes in the world. It's been erupting on and off for hundreds of thousands of years.
All of Hawaii is a tourist destination, but this particular eruption wasn't in an area where most tourists go. The homes at risk are in a subdivision near the town of Pahoa.
Source: USA TODAY. By Doyle Rice. May 4, 2018, accessed May 5, 2018
<https://www.usatoday.com/story/news/nation/2018/05/04/hawaii-volcano-eruption-kilauea-big-island/580466002/>
________________________
Kilauea Volcano Erupts, Spewing Lava and Gases Near Homes in Hawaii
Governor David Ige has issued an emergency proclamation and has called up the National Guard to help emergency workers with evacuation efforts.
Source: THE NEW YORK TIMES. By Meghan Miner Murray, Sabrina Tavernise and Maya Salam. May 4, 2018, accessed May 5, 2018
<https://www.nytimes.com/2018/05/04/us/kilauea-volcano-eruption-hawaii.html>
Hawaii -Kilauea - Eruptions - Seismic Activity - The Earth's Core
CB-Impactite Talk_LPL revised
1. David L. Griscom
impactGlass research international
San Carlos, Sonora, México
Lunar and Planetary Laboratory, University of Arizona, March 7, 2007
2. However, during the past eight years the speaker has been
formulating the hypothesis that these “upland deposits” are
ejecta from the Chesapeake Bay crater.
Prologue
The 35.5-million-year-old, 90-km-diameter crater buried beneath
the lower Chesapeake Bay was discovered and characterized in
considerable detail in the mid 1990’s by C. Wylie Poag and his
colleagues at the U.S. Geological Survey. Its existence and
radiometric age are now universally accepted.
The origin of ~5,000 km2 of sand, silt and gravel blanketing parts
of Washington, DC, southern Maryland, and eastern Virginia had
been controversial for well over a century when Schlee (1957)
seemed to have settled the matter in favor of a fluvial model.
3. Parts of This Lecture Are Taken From:
Fossil Natural Glasses Composed of Ferric Oxyhydroxides:
Impactites of the 35.5-Million-Year-Old Chesapeake Bay Crater
by
David L. Griscom,
Ayao Akiyoshi,1 Tomotaka Homae,1 Ken-ichi Kondo,1 Chihiro Yamanaka,2 Takehiro
Ueno,2 Motoji Ikeya,2 Mario Affatigato,3 and Allison Schue3
Presented at « Natural Glasses-4 », Lyon, France 29-31 August 2002
Additional contributions by the following individuals are gratefully acknowledged:
4Guillaume Morin, 5Gabriele Giuli, 5Eleonora Paris, and 6Giovanni Pratesi
1Tokyo Institute of Technology 2Osaka University 3Coe College
4Université de Paris 6 5Università di Camarino 6Università di Firenze
Published in Journal of Non-Crystalline Solids 323 (2003) 7-26.
5. Quartzite pebbles with adhering hard red-brown iron
oxide found in the gardens of our former home in
Northern Virginia (located about 10 km south of
Washington, DC).
1
I also found a few pebbles showing
Devonian-age (~360-400 Ma) brachiopod fossils.
6. 500 μm
3 cm →
External flange
Red-brown material penetrates sandstone
to uniform depth
Thin section viewed under crossed polars
reveals fractured quartz grains “floating” in
hard red-brown matrix – without relative
rotations of the fragments!
7. Chesapeake Bay Structure
Piedmont Metamorphic Rocks
250 km
Limit of Atlantic Coastal Plain
Geology of the Eastern United States
Appalachian Mountain Anticlines
8. Geology of the State of Virginia
●
Silurian and Devonian
Sandstones
The Chesapeake Bay Structure
This and other similar maps taken from K. Frye, Roadside Geology of Virginia (Missoula Press, 1986)
Piedmont Coastal Plain
Fall Line
9. Geology of U.S. Mid-Atlantic Coastal Plain
Sandstones:
Silurian
Washington, DC
Upper Chesapeake Bay
Silurian and Devonian
Sandstones
Hypothetical Anticlines ~200 Million Years Ago, Now Eroded
Sand, Gravel
and Clay (Soft)
Ancient
Metamorphic
Rocks (Hard)
A Syncline
, Devonian
“Upland Deposits”
10. Examples of Upland Gravels from the Speaker’s
Neighborhood (Alexandria, VA)
0 1 2 3
0
20
40
60
Cobble Size (mm)
NumberCount
Un-Fractured
Single Fracture
Two or More
Fractures
32 64 128 256
Silica-based optical fibers without
surface flaws require application
of ~5 GPa tension to fracture.
When they do fail, a characteristic
“mirror-mist-hackle” pattern is
observed.
11. The “Upland Deposits” of Southern Maryland:
A 1957 Field Study/Review Article by John Schlee
BULLETIN OF THE GEOLOGIAL SOCIETY OF AMERICA
VOL. 68, PP. 1371-1410, 21 FIGS. OCTOBER 1957
UPLAND GRAVELS OF SOUTHERN MARYLAND
By John Schlee
First sentence in the Introduction:
First sentences of sixth paragraph:
The origin of the southern Maryland upland deposits is controversial.
First geologic studies of the region date back to the early 1800’s, but the most
definitive work was done in the last 75 years. (WJ McGee, 1888; 1891; Darton,
1891; 1893; 1894; 1939; 1951; Cooke, 1930; 1932; 1941; Cooke et al., 1952;
Stephenson et al., 1932; Dryden and Overbeck, 1948; Carr, 1950, Hack, 1955).
60 years!
It is my impression that the model due to Hack (1955) became
universally accepted shortly after its reluctant adoption by
Schlee (1957) … who carefully noted a host of contradictions.
40 pages! 50 years ago!
12. The “Upland Deposits” of Southern Maryland:
A 1957 Field Study/Review Article by John Schlee
According to Schlee (Bull. Geological Society of America 68, 1371, 1957):
Geology:
A “sheetlike deposit” ~9 m deep dipping southeastward from
Washington, DC, covering ~1,600 km2 of southern Maryland
● A Petrological Oddity within the “Upland Gravels”:
“Secondarily introduced iron oxide locally cements the sand and
gravel along definite zones and in large irregular masses up to 3 feet
across”
• Lithology:
(1) an upper “loam member” (~90% quartz silt) ~8 m thick
(2) a lower “gravel member” (mostly sandstone) ~1 m thick
Loam
90% Quartz
~1 cm
9 m
~1 m
“Upland Gravels”
“Peanut Brittle-Like”
13. Soft coastal plane sediments
“Upland Deposits” of Southern Maryland
Currently Accepted Emplacement Mechanism (Hack, 1955; Schlee, 1957)
Silurian &
Devonian
Sandstone
Outcrops
Blue Ridge
Water Gap
Fall Line Mouth of
Potomac
River
Erosion
~65 km
~120 km
~65 km 128 mm Cobbles
• Geologists presently believe this process to have taken place within the past 10 million
years
• This scheme models the 1-m deep “gravel member” only.
— 37 years before the discovery of the crater!
Shenandoah R.
Potomac River
“Ancestral” Potomac River
Transport Without Deposition Deposition Without Erosion
…and that the 75-year controversy regarding origins had been resolved in 1957
14. Devonian
Sandstone
Outcrops
~85 km
Tysons Corners, VA District of
Columbia
~100 km
Schlee (1957): “Modern Potomac River gravel …is quite different
in composition from that of most of the upland gravels.”
100 m
125 m
Vein Quartz Modern Potomac River
Sea Level
Piedmont
Metamorphic
Rocks
(Hard)
“Upland Deposits” of Southern Maryland
As They Appear Today (Schlee, 1957)
SENW
Coastal-Plain
Sediments
(Soft) ~1 m
~8 m
15. “Upland Deposits” of Southern Maryland
A Contemporary Schematic Cross Section
N.B. “Upland deposits” are not present here in this section.
However, they do occur at these elevations ~25 km west
(at Tysons Corners).
after USGS (2000)
Eocene
Paleocene
Miocene
The base of “upland deposits” dips at ~1 m/km for ~100 km
My hypothesis: Base was sculpted by “jetting” phase of the impact.
NW SE
Crater 120 km
Miocene (?)Potomac River
Meters
150 –
100 –
50 –
0 –0 –
-50 –
-100 –
…and it exhibits no hint of ancient shorelines!!!
16. Interpretation adverse to the present
hypothesis:
“Upland Deposits”
Current Mapping in Maryland
This Map Published 2000 by:
U.S. Department of the Interior
U.S. Geological Survey
District of
Columbia
The “Upland gravels” are
mapped by geologists as overlying
formations (e.g., the Calvert Formation)
that are regarded as younger than the
Chesapeake Bay crater.
There is no way to duck the
stratigraphic superposition principle.
I will tell you shortly how I deal with it.
●
“Upland Deposits”
of Southern
Maryland
But first, more from John Schlee…
17. The “Upland Deposits”
Data, Analyses, and Quotes from John Schlee (1957)
Schlee gives four distinct reasons
why the “upland deposits” could not
have formed in their present locations
as an alluvial fan!
Schlee’s cumulative frequency
distribution of sorting coefficients of
the upland gravels is “suggestive of
an alluvial fan deposit.”
Log2(Size in mm)
“The loam member was not
investigated, but structures and
textures of the gravels were studied
at 98 localities.”
“Most of the coarser fractions of the
gravels are ‘vein’ quartz, quartzite,
and chert” (α-quartz forms of SiO2).
4 8 16 32 64 128 256 mm
Note the cut-off for streams!
“Anomalous”
boulders up to
~4 m3 are also
found among the
upland deposits!
So by process of
elimination, he returned to a fluvial
model, ignorant of the existence of the crater!
18. The “Upland Deposits”
Gravel-Size Data and Analyses of John Schlee (1957)
-6.0 -5.5
-4.5
-4.0
-5.0
-3.5
-3.0
-2.5
-2.0
Washington, DC
N.B. Schlee’s gravel-size contours
are labeled by the negative log to
the base 2 of the observed modal
sizes (so-called “phi units”).
Noting that the contours were
more or less equally spaced in phi
units, Schlee (1957) perceived a
possible exponential progression.
To test this notion, he took four
additional sets of gravel-size data
along four approximately-linear
paths running generally
southeasterly of the U.S. Capitol.
19. 128 mm
The “Upland Deposits”
Gravel-Size Data and Analyses of John Schlee (1957)
Direction of the Center
of the Chesapeake Bay Crater
Mean Direction of
Apparent Dip of the
Gravel Exposures
Washington, DC
0 10 20 30 40 50 60
2
3
4
5
6
Ancient Potomac River (?)
Cobble Size Reduction Rates
Rhine River
Mur River
ModalGravelSize(PhiUnits)
Distance (km)
32 mm
16 mm
8 mm
4 mm
My Interpretation:
Atmospheric size
sorting of ejecta
in flight.*
-6.0 -5.5
-4.5
-4.0
-5.0
-3.5
-3.0
-2.5
-2.0
-
-
-
-
-
Extrapolates to 128-mm cobbles at ~15 km
northwest of Washington, DC – where
most rocks this size are petrologically
different from the upland gravels!
*Schultz, Gault
(1979)
64 mm
+
20. The “Upland Deposits” of Southern Maryland
Model of Hack (1955) and Schlee (1957):
Deposition by the Potomac River ~10 to ~3 Million Years Ago
Problem: Schlee’s cobble-size
gradient extrapolates to a source region
~15 km NW of Washington, DC ( ), but
no major outcrops of quartzite are found
there! The nearest potential source of
the Devonian quartzites in the “upland
deposits” is ~135 km to the west!
Problem: The “upland deposits” are
far larger than the region studied by
Schlee.
Problem: The cobble-size gradients
are much too large for a river unable to
cut a deep channel in the “soft easily
eroded Coastal Plain sediments” that
underlie the “upland deposits”.
25 km
They extend far southward…
Laterally migrating channel
growing ~1 m deeper per
kilometer of sideways displacement
Ancient
Potomac
River
Courses
21. “Upland deposits”
of southern Maryland
(studied by Schlee (1957))
Richmond, VA
Washington, DC
Gravity map showing negative
gravity anomaly coinciding with
the inner basin of the Chesapeake
Bay structure. The position of the
outer rim is shown as
the dashed curve.
(After Koeberl et al.,
1996).
“Upland deposits”
of eastern Virginia
(Frye, 1986)
22. The Chesapeake Bay Impact Structure
(Cross section from Koeberl et al., 1996 and Poag, 1997)
Koeberl et al. and Poag: The Lower-Cretaceous target rocks are
poorly-lithified, non-marine, mainly siliciclastic sediments ~500 m thick.
Griscom: It seems possible that these target rocks included alluvial
deposits rich in Devonian quartzite gravels – exactly matching the
description of the “upland deposits”.
400-360 Ma (Devonian): Quartzite sandstones deposited
Time
250 Ma: Appalachian Mountains folded, uplifting anticlines of Devonian quartzites
140-100 Ma (Lower Cretaceous): Alluvial fans crept seaward from the Appalachians
35.5 Ma: Impact!!!
My View:
25. The “jetting” stage is
well known in cratering
physics …but this may
represent the first ever
appeal to jetting in an
attempt to explain an
actual geological feature
on the face of the Earth.
15-cm Ball of Marine Chalk
Found in an Upland Depression
(Sliced Cross Section)
Note “toasted” exterior and
shattered (brecciated) interior.
My Model for the
Jetting-Phase:
The Ocean – and the
Soft Coastal Deposits –
Are Chamfered at an
Angle of ~0.06o
Present day
slope of the base
of the “upland deposits”
-200 -100 0 100 200
-300
-200
-100
0
100
200
300
400
500
600
700
Elevation(m)
Distance (km)
26. “Upland
Deposits”
R-3
4,300 km3
(Poag, 1997)
Crater Diameter: 87 km
Energy: 18 TeraTons of TNT
Projectile Diameter: 6 km
Projectile Density: 1500 kg/m3
Impact Velocity: 30 km/s
Impact Angle: 45°
It is known from
explosion experiments
that the thicknesses of
ejecta blankets follow
the -3rd power of the
radius R from the
crater center. The
normalization factor is
determined from the
total volume of ejecta,
which in turn can be
scaled from the known
diameter of the crater.
About Ten Minutes after Impact Trial Parameters Entered into a
Crater-Size Calculation:
0.06°
-200 -100 0 100 200
-200
-100
0
100
200
300
400
500
600
700
Elevation(m)
Distance (km)
27. H.J. Melosh, Impact Cratering – A Geologic Process
(Oxford University Press, New York, 1989)
J.N. Head, H.J. Melosh, B.A. Ivanov
Science 298 (2002) 1752
The fastest interference-zone
ejecta can leave with ~0.5
times the speed vi of the
impacting object!
~2.0 Impactor Diameters
Interference-Zone
Ejecta
But let us drop back to the
first few tenths of a second…
~0.02vi
28. But let us drop back to the
first few tenths of a second…
GRANITE
Vertical
Exaggeration
X 50
Distance (km)
Chesapeake Bay Crater
10 min
“Effective”
Interference Zone
(v 0.02vi)
Frye (1986) found this granite “dropstone”
in a mudstone bed 800 km due west of
the crater center.
27-kg granite object found among the
“upland gravels” 200 km northwest of the
crater center (speaker’s front yard).
-40 -20 0 20 40
-3
-2
-1
0
1
Elevation(km)
D
Lower Limit of Interference Zone
USGS
29. “Effective”
Interference Zone
~212 km3
Vertical Exaggeration X330I propose that the “upland gravels” are interference-zone ejecta comprising
pre-formed alluvial, mostly-quartzite gravels >2 mm that were
subject to size sorting by atmospheric drag
during ballistic flight.
Tysons
Washington
-200 -100 0 100 200
-700
-600
-500
-400
-300
-200
-100
0
100
200
300
Elevation(m)
Distance (km)
30. “The Day After”About 10,000 Years LaterAbout Two Million Years Later
Calvert I & II contain mostly the same microfossils, but there are
differences.
35.5 Ma
Chickahominy Fm.
CALVERT II
“Exmore Breccia”
Glass
???
???
But if so many of these species survived the impact,
why are is the Chickahominy cohort almost totally different?
I argue that the microfossils in Calverts I and II are shallow-
water species, whereas those in Chickahominy represent
“disaster blooms” that lived here when the ocean was deeper.
<35.5 Ma
It’s about sea levels!
-200 -100 0 100 200
-700
-600
-500
-400
-300
-200
-100
0
100
200
300
Elevation(m)
Distance (km)
31. Eustatic Sea Level through Geological “Deep Time”
(Plot Taken from a Review by Hallam, 1984)
65 33 5
Chesapeake Bay
& Popigai, Russia,
both ~90 km
Chicxulub, México,
~200 km Diameter
(Dinosaurs Extinct)
Bedout High, Australia
(Greatest Mass
Extinction in Earth History)
Some Impact Craters of
Major Significance to
Earth History:
Ice Caps Form“Snowball Earth”
Silurian
Devonian
Permian
Triassic
Jurassic
Cretaceous
Eocene
Miocene
Pre-Appalachian
Sandstones
Deposited
Appalachian
Mountains
Uplifted
Appalachian
Mountains
Eroded
Atlantic Ocean Opens
Most sea-level changes during this interval are presumed due to changes in sea-floor geometry.
32. Can an Impact Cause an Ice Age?
…Provided the Impact Can Create a Ring Around the Earth!
The Answer Is a Definite “Maybe”
Recent Photographs from the NASA Cassini-Huygens
Space Probe at Saturn
Note Ring Shadows Falling on the Winter Hemisphere!
33. Climatic Effects of an Impact-Induced Equatorial Debris Ring
(P.J. Fawcett, M.B.E. Boslough, J. Geophys. Res. 107, No. D15, 2002)
Oblique impacts between 10° and 20° can insert debris into earth orbit (Schultz & Gault, 1990)
Fawcett and Boslough (2002) calculated effects of a ring-forming impact on Earth’s climate,
which included severe cooling, sea ice, and polar ice-cap formation. These authors suggest
that the Chesapeake Bay (or Popigai) impact may have been a ring-forming one.
34. “The Heartbeat of the Oligocene Climate System”
H. Pälike et al., Science 314, 22 December 2006, 1894-1898.
36.3 Ma
35.2 Ma
The authors measured a 13-million-year continuous record of Oligocene
climate from a Pacific Ocean Drill core.
“Ages and step functions on right side illustrate the changes in silicate weathering
applied to each model in order to simulate the onset of the Oligocene icehouse.”
Maybe the end-Eocene comet shower DID restore Earth’s ice caps!!!
Mi-1 Oi-1
35. Response of Eustatic Sea Level Due to Polar-Ice-Cap Formation:
A Major Constraint on Coastal-Plane Deposition Rates
Chesapeake Bay Impact (35.5 Ma)
Triassic
Jurassic
Cretaceous
Eocene
Miocene
Recent
155 m
65 m
0 m
-140 m
Oligocene
250 65 24 5
Time (Millions of Years)
Arctic Ice Sheets
Antarctic Ice Sheets
Global deep-sea drill-core 18O studies
by Zachos et al., Science 292, 686 (2001)
SeaLevel
(metersabovepresent)
The highest point of the
Calvert Formation in
southern Maryland is
about 70 m above
present sea level.
Thus, a sea-level high
stand >70 m would have
been required to deposit
Calvert I.
33.7
CALVERT I
It’s about sea levels!
It follows that
Calvert I was more likely
deposited earlier than
~34 Ma.
-
-
-
-
-
-
- (Hallam, 1984)
~2 My
00
36. Aquifers presumably containing
precipitated iron oxides
Stratigraphy
of U.S. Mid-Atlantic
Coastal Plain
(Figure from Poag, 1997)
TABB FM
SHIRLEY FM.
BACONS CASTLE FM
“UPLAND DEPOSITS”
The accepted stratigraphy of
the U.S. Mid-Atlantic Coastal
Plain was determined before the
discovery of the Chesapeake
Bay crater
On the basis of several lines of
evidence I have argued that the
“upland deposits” have been
chronologically misplaced in the
this scheme and are in fact crater
ejecta.
I have just argued that there
are two (diachronous) Calvert
Formations, not just one.
CALVERT I
CALVERTCALVERT II
Now –
-
10 Ma –
-
20 Ma –
-
30 Ma –
-
40 Ma –
-
50 Ma –
-
60 Ma –
-
70 Ma –
Geologic Time
35.5 Ma
Hiatuses
and has changed very
little since.
140 Ma
11-28 My
Hiatuses!
Other units must change
too…
37. The “Upland Deposits” of Southern Maryland:
A 1957 Field Study/Review Article by John Schlee
According to Schlee (Bull. Geological Society of America 68, 1371, 1957):
Geology:
A “sheetlike deposit” ~9 m deep dipping southeastward from
Washington, DC, covering ~1,600 km2 of southern Maryland
• Lithology:
(1) an upper “loam member” (~90% quartz silt) ~8 m thick
(2) a lower “gravel member” (mostly sandstone) ~1 m thick
Loam
90% Quartz
~1 cm
9 m
~1 m
“Upland Gravels”
● A Petrological Oddity within the “Upland Gravels”:
“Secondarily introduced iron oxide locally cements the sand and gravel
along definite zones and in large irregular masses up to 3 feet across”
N.B. These things are the same size as the “spall plates” predicted to be launched
at high speeds as coherent clods of interference-zone ejecta (Melosh, 1987, 1989).
~1 m
38. Red-Brown Materials: Energy Dispersive Analysis
EDX scan was recorded for a quartz-free spot in the red-brown matrix.
Quartz
The
Matrix
Is Nearly
Pure Iron
Oxide!
Fe
Fe
P
SiAlOC
(Data compliments of J. Quick, USGS)
SEM
Fe
keVQuartz grains are “floating” in an iron-oxide matrix!
39. Red-Brown Materials: X-Ray Diffraction
(Guillaume Morin, Université de Paris 6)
Orange curve is a simulation based on (1) catalog parameters for α quartz and
(2) fitted parameters for goethite (α FeOOH) in particle sizes ~100x150 Å.
These results, together with Mössbauer data, suggest the possible co-presence
of an amorphous-ferric-oxyhydroxide component.
20 40 60 80 100 120
10
3
10
4
Co K
041
131
140
021
231
002
151
160
221
130
110
020
Counts
Angle 2 (Degrees)
40. No Stone Left Unturned
Schlee (1957) reported these things to be common, but…
It took me many months to amass this collection by digging in our yard
in Alexandria, VA.
I found a few other unspectacular examples 50 km south in Aquia, VA…
41. No Stone Left Unturned
Then one day…
I noticed a couple piles of rocks in a vacant lot in the next subdivision.
They’d been trucked in from an excavation in Springfield, VA, 8 km west.
cm
42. Now I began to cut these rocks with diamond saws.
Missing
Spall
Internal Fractures
with No External
Expression
Dark Stains
Contiguous
with the Flanges
Penetrate
Solid Rock!!
External Flanges Join Rocks Together
No Stone Left Unturned
Jackpot!
I will show that all of these features can have been made by shock waves
– and probably in no other way.
New!
New!
43. Staining of Quartzite Clasts by Fe Oxyhydroxides
Empty
Fractures
Mild Staining
Unstained
The reason for internal “staining” is
that the iron oxide has intruded the
rock by expanding the spaces between
individual quartz grains.
Iron oxide fills the internal fracture in
the magnified area, but the rest of the
fracture is empty! This effect cannot be
due to in-diffusion of aqueous solutions! Next Slide
Slide After
Next
44. Now let’s now compare the above cobble
from Springfield, VA, with the pebble from
my backyard (8 km to the east).
Geologists currently interpret these ferric
oxyhydroxides as “bog iron”.
Quartz Grains “Floating” in an
Iron-Oxide Matrix!!!
Among the problems with attributing the present
ferric oxyhydroxides to bog iron are the absolute
absence of organic material – and the necessity to
“levitate” the quartz grains during precipitation.
500 μm
500 μm
But if the iron oxide were originally a viscous melt,
it could have been quenched into its present solid
form replete with inclusions that appear to “float.”
“Melt-matrix breccias” are well known results of
impacts, although similar things also occur in
volcanic lavas. However, there are no known
volcanic lavas that consist of pure iron oxide.
Conclusion: These things can have been made
only by impact!
Bog iron is a well known phenomenon on the U.S.
mid-Atlantic Coastal Plane, and is due to oxidation
of Fe2+ in spring-water-fed bogs.
Such things are called “melt-matrix breccias.”
(with bog iron present in the target?)
45. Quartz Grains Interior to the Same Pebble:
Comparison to Sandstone Ejecta from Meteor Crater, Arizona
Same
“uplands
deposits”
stone as
illustrated
in the two
previous
slides
(crossed
polarizers)
800 m 200 m
Coconino
Sandstones
from Meteor
Crater, AZ.
Source:
B.M. French,
Traces of
Catastrophe
(Lunar and
Planetary
Institute,
Houston,
1988) “moderately shocked” “highly shocked”
46. Energy Dispersive Analysis
(M. Affatigato and A Schue, Coe College, USA)
Bulk analyses by energy-dispersive x-ray fluorescence
Data are modeled here as “Fe2O3” diluted by quartz
1
3
2
1 2
3
Weight Percent Fe2O3
WeightPercent
Impurity contents in “Fe2O3” are extrapolated: ~1% each Si, Al, P, K
47. Scanning Electron Spin Resonance Imaging
(Motoji Ikeya et al., Osaka University)
Measured paramagnetic species was radiation-induced E´ centers in quartz.
Factor of 2
I had anticipated the possibility that the E´ centers might have annealed out in
the stained regions 35.5 My ago (time of impact) but that a full 400-My-worth
of (Devonian age) centers could have survived in the white part. I was wrong.
I am instead compelled to ascribe the observed intensity variations to
shock-induced introduction and/or redistribution of radionuclides, most likely
40K (τ1/2 = 1.3109 yr)., correlated with the presence of the iron oxide.
48. Experimental Shocking
(Ken-ichi Kondo et al., Tokyo Institute of Technology)
(a)
(b)
(c)
(d)
(a) Amorphous ferric
oxyhydroxides and/or
nanocrystalline
goethite in a thin
section of “upland
deposits” rock.
quartz+goethite sample
(b-d) Laboratory shocked
α-FeOOH-quartz-
powder bi-layers.
200 m
50 m
49. Experimentally Shocked Samples Should Be Subjected to
Further Studies
The following model is proposed for the effect of shock on Goethite:
2FeOOH(normal crystals) + shock 2FeO2 (silica-like Fe4+ glass) + H2
In the event the above mechanism should be correct, then the present upland
materials might have resulted from the following diagenetic reaction:
36FeO2 (glass) + 12H2O 24FeOOH (xtalites ~10 nm) + 6Fe2O3 + 9O2
The mineral Goethite has hardness 5-5.5 and perfect cleavage along one plane.
The Hard Ferric Oxyhydroxides of the “Upland Deposits”
Should Be Also Subjected to Further Studies
By contrast, the ferric oxyhydroxides of the “upland deposits” universally exhibit
conchoidal fracture and appear from scratch tests to be harder than quartz (>7)!
In fact, the majority of the hard ferric oxyhydroxides endemic to the “upland
deposits” appear to have suffered conchoidal fracturing prior to their
emplacement!
50. 2v
U
UR
Internal Fracture
Shock Pressure Wave
Infinite
Planar
Surface
Pressure ≈0 in interference zone
UR
UR
U
U
Spall
An Example from the “Upland Gravels”
Pressure
(N.B. This geometry is more
complicated than an
infinite plane.)
— but forward-moving particle velocities are doubled!
Missing
Spall
Shock Effects
H.J. Melosh (1989): Impact Cratering
A Geologic Process
2V
Elastic
Solid
Reflected Rarefaction
(Tensional) Wave
2V
51. Model for Iron-Oxide Melt Sheets Shock-Induced in Water
Containing Precipitate Ferric Oxyhydroxides
Distance
(a) Profile of a shock pulse (Melosh, 1989) (c) Water vaporizes, consuming pulse tail
Suspended ferric oxyhydroxides melt, and melt sheet may overtake pressure pulse.
Water
Steam
Vacuum Water
Steam
U+ε
(b) Water cavitates in wake of shock wave
(d) The evaporating surface is accelerated
forward, concentrating suspended particles.
52. Model for Shock-Induced Iron-Oxide Melt Sheets Penetrating
Sandstone Cobbles
Transmitted
Pulse
First Reflection
Vacuum
Distance
I
II
III
IV Second Reflection
Unstained Rock
Spall
Probable fossil
record of multiple
reverberations
Water (not shown elsewhere)
Shock Front
(Pressure Pulse)
Iron oxide melt sheet overtakes rock
Reflected Pulse
(Rarefaction)
Pressure Pulse Pushes Fe-Oxide
Melt into Inter-Granular Spaces
Opened by the Rarefaction Pulse
53. Conclusions
The “upland deposits” of the U.S. Mid-Atlantic Coastal Plain…
were created 35.5 million years ago by shock waves passing through
wet siliciclastic sediments (including Devonian quartzite gravels) present
in the target area of the Chesapeake Bay impactor (Koeberl et al., 1996).
The gravel member of the “upland deposits” is here imputed to
interference-zone ejecta (Melosh, 1989) from the Chesapeake Bay crater .
The extreme cobble-size gradient reported by Schlee (1957) is thus
reasonably ascribed to atmospheric size sorting (Shultz and Gault, 1979).
Schlee’s (1957) alluvial-fan statistics for the “upland gravels” plausibly
indicate that the lower-Cretaceous target rocks included alluvial sediments.
Iron oxyhydroxides precipitated in aquifers of the target area were
concentrated and melted by impact shock waves. These ~1-cm-thick melts
penetrated, entrained, and finally welded target gravels into irregular
masses 1 m (Schlee, 1957), interpretable as “spall plates” (Melosh, 1989).
54. What Does the Future Hold?
If and when a reproducible 40Ar-39Ar date
is obtained for the ferric oxyhydroxides of
the “upland deposits”, I will finally be
proved right
If I am right, it will be a bonanza for impact
geology, since the “upland deposits” would
then become the best preserved, most
extensive, and most accessible ejecta of
any major crater on the surface of the
earth.
Among the possible scientific treasures
one could hope to extract from these
deposits might be rocky fragments of a
cometary nucleus!
…or wrong.