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Magnetic reversal is a process where the Earth's magnetic poles switch places. The magnetic field reverses approximately every 400,000 years, as shown by magnetic stripes in volcanic rocks on the seafloor. These reversals are caused by changes in the flow of the Earth's liquid outer core. Studying the magnetic patterns in seafloor rocks provides evidence for the theory of seafloor spreading, as it allows scientists to construct a record of past magnetic polarity.
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Earthquakes and faults
An earthquake is caused by the sudden release of stored energy in the Earth's crust that creates seismic waves. Faults in the Earth's surface develop from movement or displacement of rock and are zones of weakness where earthquakes can occur. There are three main types of faults - strike-slip, normal, and reverse - which are defined by the movement of the rock on either side. Seismographs use a pendulum that remains fixed while the ground moves beneath it to record the intensity and duration of seismic waves, including primary P waves, secondary S waves, and surface L waves, generated by earthquakes.
18. magnetic reversal
This document contains a detailed lesson plan for a Grade 10 Science class on magnetic reversals and seafloor spreading. The plan outlines the objectives, topics, materials, procedures, and evaluation for a 60 minute lesson. Students will analyze a magnetic polarity map, calculate seafloor spreading rates, and present their findings. They will learn that magnetic reversals are caused by changes in Earth's core and prove seafloor spreading by magnetic patterns in ocean floor rocks. The lesson aims to help students understand how new seafloor is created at mid-ocean ridges and how this relates to plate tectonics.
Sea floor spreading
Scientists in the 1950s used sonar to map the mid-ocean ridge and discovered it was not flat but contained underwater mountains. This discovery led them to research what the ridge was and how it formed. Evidence from molten rock samples, magnetic stripes in the ocean crust, and the ages of rocks drilled from the ocean floor supported Harry Hess' theory from 1960 of sea-floor spreading, where new crust forms at mid-ocean ridges and spreads outward over time.
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Platetectonics theory
The document discusses plate tectonic theory and provides evidence for plate tectonics. It explains that the lithosphere is broken into plates that move atop the asthenosphere due to convection currents in the mantle. There are three types of plate boundaries - divergent where plates move apart, convergent where they move together, and transform where they slide past each other. Plate tectonics helps explain geological phenomena like volcanoes, earthquakes, and mountain building.
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This document discusses three main types of plate boundaries: divergent boundaries, convergent boundaries, and transform boundaries. It provides examples and describes the geological effects of each boundary type. It also discusses processes at divergent boundaries like mid-ocean ridges and continental rift valleys. Convergent boundaries include oceanic-oceanic convergence forming island arcs, and continental-oceanic convergence forming volcanic mountain ranges. Transform boundaries involve strike-slip faulting along plate edges. Additionally, the document touches on hot spot volcanism unrelated to plate boundaries.
Seafloor Spreading
Earth and Life Science
Earth Materials and Processes: Deformation of the Crust
The learners shall be able to:
1) explain how the seafloor spreads (S11/12ESId-23);
2) describe the structure and evolution of ocean basins (S11/12ES-Id-24); and
3) explain how the movement of plates leads to the formation of folds and faults (S11/12ES-Id-22).
Specific Learning Outcomes
At the end of the lesson, the learners will be able to:
1. Discuss the history behind the Theory of Continental Drift;
2. Describe the Continental Drift Theory;
3. Enumerate and explain the evidence used to support the idea of drifting continents;
4. Identify major physiographic features of ocean basins
5. Describe the process of seafloor spreading
Lesson 1_Science 10 -Q1W1_ Distribution of Volcanoes, Earthquake Epicenters, ...
1. There are three major volcanic belts in the world along plate boundaries: the Circum-Pacific Belt, Mid-Atlantic Belt, and Mid-Continental Belt.
2. The Circum-Pacific Belt, also known as the Pacific Ring of Fire, experiences the most earthquakes and contains the highest concentration of volcanoes due to the collision of tectonic plates. Approximately 70% of the world's earthquakes occur in this region.
3. Mountain ranges are predominantly located along the Circum-Pacific Belt, including the Himalayas which contain the highest mountain peaks and were formed by the collision of the Indian and Eurasian plates
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This document contains a detailed lesson plan for a Grade 10 Science class on magnetic reversals and seafloor spreading. The plan outlines the objectives, topics, materials, procedures, and evaluation for a 60 minute lesson. Students will analyze a magnetic polarity map, calculate seafloor spreading rates, and present their findings. They will learn that magnetic reversals are caused by changes in Earth's core and prove seafloor spreading by magnetic patterns in ocean floor rocks. The lesson aims to help students understand how new seafloor is created at mid-ocean ridges and how this relates to plate tectonics.
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Scientists in the 1950s used sonar to map the mid-ocean ridge and discovered it was not flat but contained underwater mountains. This discovery led them to research what the ridge was and how it formed. Evidence from molten rock samples, magnetic stripes in the ocean crust, and the ages of rocks drilled from the ocean floor supported Harry Hess' theory from 1960 of sea-floor spreading, where new crust forms at mid-ocean ridges and spreads outward over time.
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This document discusses three main types of plate boundaries: divergent boundaries, convergent boundaries, and transform boundaries. It provides examples and describes the geological effects of each boundary type. It also discusses processes at divergent boundaries like mid-ocean ridges and continental rift valleys. Convergent boundaries include oceanic-oceanic convergence forming island arcs, and continental-oceanic convergence forming volcanic mountain ranges. Transform boundaries involve strike-slip faulting along plate edges. Additionally, the document touches on hot spot volcanism unrelated to plate boundaries.
Seafloor Spreading
Earth and Life Science
Earth Materials and Processes: Deformation of the Crust
The learners shall be able to:
1) explain how the seafloor spreads (S11/12ESId-23);
2) describe the structure and evolution of ocean basins (S11/12ES-Id-24); and
3) explain how the movement of plates leads to the formation of folds and faults (S11/12ES-Id-22).
Specific Learning Outcomes
At the end of the lesson, the learners will be able to:
1. Discuss the history behind the Theory of Continental Drift;
2. Describe the Continental Drift Theory;
3. Enumerate and explain the evidence used to support the idea of drifting continents;
4. Identify major physiographic features of ocean basins
5. Describe the process of seafloor spreading
Lesson 1_Science 10 -Q1W1_ Distribution of Volcanoes, Earthquake Epicenters, ...
1. There are three major volcanic belts in the world along plate boundaries: the Circum-Pacific Belt, Mid-Atlantic Belt, and Mid-Continental Belt.
2. The Circum-Pacific Belt, also known as the Pacific Ring of Fire, experiences the most earthquakes and contains the highest concentration of volcanoes due to the collision of tectonic plates. Approximately 70% of the world's earthquakes occur in this region.
3. Mountain ranges are predominantly located along the Circum-Pacific Belt, including the Himalayas which contain the highest mountain peaks and were formed by the collision of the Indian and Eurasian plates
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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.
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Magnetic reversal occurs when the Earth's magnetic poles flip so that the North Pole becomes the South Pole and vice versa. Scientists can detect magnetic reversals by studying the magnetic minerals in volcanic rocks on the seafloor. As the rocks cool from lava, the magnetic minerals align with the Earth's magnetic field at that time. The pattern of alternating magnetic stripes on opposite sides of seafloor spreading ridges provides evidence that the seafloor is spreading. On average, there are 4-5 magnetic reversals per million years, and the matching magnetic patterns on opposite sides of ridges indicate the seafloor is spreading at a rate of about 2.5 cm per year.
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To locate an earthquake epicenter using triangulation, seismologists determine the S-P interval from seismograms of at least three seismic stations. This interval is converted to epicentral distance and circles are drawn on a map with radii equal to these distances. The intersection of these circles identifies the epicenter. Triangulation is suitable for local quakes, while distance-time graphs are used for more distant quakes. Locating epicenters helps identify active fault lines and areas at risk for future major quakes due to long periods of inactivity on certain faults.
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This document provides an overview of plate tectonics and the evidence that supports the theory. It discusses how early scientists like Alfred Wegener proposed that continents move over time (continental drift). Wegener noticed matching land features and fossil evidence between continents. Later, Harry Hess confirmed Wegener's ideas by discovering that new crust forms at mid-ocean ridges, providing evidence of sea-floor spreading as plates move apart. Convection currents in the mantle caused by heat from the Earth's core are now understood to drive the movement of tectonic plates.
1. Earthquake and Faults
Convection currents in the earth's mantle cause the movement of tectonic plates. Faults form at the boundaries of these plates where the rocks are weak. When stress builds up along fault lines from the movement of plates, it causes the faults to slip suddenly and generate earthquakes. There are three main types of faults - normal, reverse, and strike-slip - which move in different ways due to tensional, compressional, or shear stresses. Active faults have generated earthquakes within the last 10,000 years and may continue to do so, while inactive faults have not produced quakes recently but could still be capable of generating future seismic activity.
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Scientists used new techniques like sonar and submersibles in the 1950s-1960s to better observe the ocean floor. They discovered mid-ocean ridges and the theory of seafloor spreading, where new crust forms at ridges and pushes plates apart over time. The movement of plates causes the splitting of continents and creation of oceans. Magnetic patterns in ocean crust provided evidence that seafloor spreading occurs and plates have moved over millions of years.
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The document provides evidence that supports the theory of plate tectonics. It describes how the continents were once joined together in a supercontinent called Pangaea hundreds of millions of years ago. It presents fossils of the same species found on different continents separated by oceans, indicating the landmasses were once closer. Additionally, fossils of tropical plants have been found in arctic areas and signs of past glaciation have been discovered in currently warm climates of places like South Africa. The magnetic properties of rocks also show that continents have moved over time.
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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.
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Here are the answers to the questions:
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Q2: Other scientists of Wegener's time rejected his hypothesis because he could not provide a mechanism to explain how and why the continents would move. They thought the continents were stationary.
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This document discusses different types of faults in the Earth's crust. It describes dip-slip faults as occurring at an angle of 45-65 degrees with the surface, including normal faults where the hanging wall moves down and reverse faults where the hanging wall moves up. Strike-slip faults involve lateral movement along the fault line in either a left-lateral or right-lateral direction. Oblique faults combine dip-slip and strike-slip movement. Active faults are those which have moved within the last 10,000 years and are likely to produce future earthquakes.
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The document discusses theories of the Earth's movement including continental drift and seafloor spreading. It explains that mantle convection causes lithospheric plates to move via convection currents. Hot mantle material rises and cools, sinking elsewhere, moving the plates over geologic timescales through processes like ridge push and slab pull. Plate tectonics integrates these ideas to explain volcanoes, earthquakes, and mountain building at plate boundaries.
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Lesson 6 discusses sea floor spreading and how it leads to continental drift. Magnetic field reversals recorded in oceanic crust rocks provided evidence that supported the theory of continental drift and sea floor spreading. As tectonic plates move apart, new magma fills the gap and forms new sea floor, recording the magnetic signature of the time. The older the sea floor rock, the further it is located from the mid-ocean ridge where new sea floor is being created. This magnetic reversal pattern in sea floor sediments provided strong evidence that sea floor is indeed continually being created and pushed apart as the theory of plate tectonics suggests.
Plate tectonics Theory
This document discusses plate tectonics and plate boundaries. It defines plates as rigid lithospheric slabs and plate tectonics as the process of plate motions. There are six major and 20 minor identified plates that move over the asthenosphere. Plate boundaries are where tectonic activity occurs and are divided into three types: divergent boundaries where plates move apart, convergent boundaries where plates move towards each other, and transform boundaries where plates move sideways relative to each other. Sea-floor spreading and paleomagnetism provide evidence for plate tectonics theory.
Plate tectonic Theory
1) The document discusses plate tectonics, describing the different types of plates (oceanic and continental), how there are 6 major and 20 minor tectonic plates, and the three types of plate boundaries - divergent, convergent, and transform.
2) It provides details on sea floor spreading and paleomagnetism as evidence for plate tectonics, describing how sea floor spreading occurs at mid-ocean ridges and how paleomagnetism records the magnetic properties in older rocks.
3) Plate tectonics theory postulates that the lithosphere is made up of these rigid tectonic plates that move over Earth's surface, and that geological activities occur at plate boundaries.
Seafloor magnetic polarity 2
A transform boundary is a plate boundary where plates slide past each other laterally. The San Andreas Fault in California is the closest transform boundary to us.
Earth's magnetic field periodically reverses polarity over geological time. When this happens, newly formed igneous rocks record the change, with magnetic minerals aligning to the new field orientation. By examining the alternating normal and reversed polarity bands in sea floor sediments on both sides of mid-ocean ridges, scientists can see evidence of past magnetic field reversals that provide information about plate tectonic movements over time.
Seafloor spreading theory discuss 3
1. Harry Hess proposed the theory of seafloor spreading in 1962, which provided evidence that Wegener's theory of continental drift was correct. Hess theorized that new ocean crust is formed at mid-ocean ridges through volcanic eruptions and then spreads outwards, pushing older crust farther away.
2. Evidence for seafloor spreading includes rock formations only possible from cooled lava, magnetic stripe patterns in ocean crust recording reversals of Earth's magnetic field, and drilling samples showing younger rock nearer to ridges.
3. Seafloor spreading is driven by convection currents in the Earth's mantle; subduction zones allow parts of ocean crust to sink back into the mantle and regulate ocean size.
Earthsmagnetism 120427184625-phpapp01
The document discusses the history and theories of Earth's magnetism. It explains that ancient Chinese and Greeks discovered magnetic rocks that pointed north. In 1600, William Gilbert proposed that Earth itself acts as a giant spherical magnet based on his experiments. This led to the question of what causes Earth's magnetism. Early theories proposed Earth's core was a permanent magnet, but this was disproven. Later, the dynamo theory emerged, attributing magnetism to electric currents in Earth's liquid outer core driven by convection. Paleomagnetic studies of fossil magnets in rocks support that Earth's magnetic poles have reversed many times.
Magnetic Earth
Sir William Gilbert hypothesized in the late 1500s that Earth acts as a giant magnet, explaining why compasses point north. While Earth's core is too hot to be the source of magnetism, the circulation of molten material in the core is related to Earth's magnetic field. Earth's magnetic poles are located in northern Canada and Antarctica, differing from the geographic poles. Earth's magnetic field can magnetize ferromagnetic materials like iron over long periods of time.
Earth's magnetism
The document discusses the earth's magnetism and how it was studied over time. It explains that early civilizations noticed magnetic properties in rocks and how compasses were used for navigation. William Gilbert conducted experiments in 1600 which showed that the earth acts like a giant bar magnet. The dynamo theory later emerged to explain the earth's magnetic field as being generated by convection currents in the liquid outer core. Studies of ancient rocks have provided evidence that the polarity of the earth's magnetic field has reversed many times in the past.
Lithosphere
Ophiolites provide evidence for the composition and structure of oceanic crust and the upper mantle. They represent sections of oceanic crust and upper mantle that have been obducted or thrust onto continental margins. Studying ophiolites like the Samail ophiolite in Oman has helped scientists understand the layered sequence of rocks that make up oceanic crust, including extrusive basalts, dikes, and intrusive gabbros.
Evidence in support of continental drift
Continental drift is supported by evidence from paleoclimatology, paleoglaciation, fossil correlation, and paleomagnetism. Paleoclimatology shows that coal deposits, which form in tropical areas, exist in high northern latitudes because the continents were once located farther south. Fossil correlation finds matching fossils on separated continents. Paleomagnetism finds that ancient lava flows on separated continents recorded the same magnetic field orientation when the lava solidified, indicating the continents were once joined.
Ch 7-2 pp.ppt
1) Scientists discovered an underwater system of ridges and valleys on the ocean floor similar to those on continents using sound waves to map the seafloor. 2) In the 1960s, Harry Hess proposed the theory of seafloor spreading to explain movement of the ocean floor. He suggested hot material rises at mid-ocean ridges, spreads the seafloor apart as new material is created. 3) Evidence for seafloor spreading includes samples showing the youngest rocks are at ridges, with older rocks farther away, and magnetic patterns in rocks aligning in strips parallel to ridges from magnetic field reversals.
Earth's magnetism
The document discusses the dynamo theory of the Earth's magnetism. It proposes that electric currents produced by the movement of liquid iron in the Earth's outer core generate the planet's magnetic field. Convection currents provide the energy needed to sustain the magnetic field over geological timescales. Paleomagnetic studies of fossil magnetism in rocks support the idea that the Earth's magnetic poles have reversed polarity multiple times in the past, consistent with the dynamo theory.
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- 1. EARTH SCIENCE: Magnetic Reversal Sir Dennis Ar N. Espiritu 10th Grade
- 2. LEARNING OBJECTIVES: a. Explain what is magnetic reversal; and b. Describe magnetic reversal as an evidence of Seafloor Spreading Theory.
- 3. Magnetic Reversal 01 What is magnetic reversal?
- 4. Definitions of Magnetic Reversal ● The process by which the North pole is transformed into a South pole and the South pole becomes a North pole. ● It is mainly generated in the very hot molten core of the planet and has probably existed throughout most of the Earth's lifetime. ● Reverse of a dipole magnetic field.
- 5. Definitions of Magnetic Reversal ● Also, called Magnetic Pole Reversals, or Magnetic “Flip”. ● Moreover, it happens two poles (dipole) switch places. #
- 6. HOW DOES THIS LOOK LIKE? The last magnetic reversal happened between 772,000 and 774,000 years ago.
- 8. About 1000 years 100 times in the past 20 millions years It takes for a magnetic reversal to complete in Each time it flips— up to DID YOU KNOW? Reversal occurs 4 or 5 times per million years
- 9. The Cause 02 What causes magnetic reversal?
- 10. The poles of magnetic field reverses due to the change in the direction of flow in the outer core. Why is there a magnetic reversal ? How is this possible?
- 11. When lava solidifies, iron bearing minerals crystallize. As these crystallize, the minerals behave like tiny compasses align with the Earth’s magnetic field.
- 12. The Location 03 Where can we find these magnetic rocks?
- 13. The occurrence of magnetic reversals can be explained through the magnetic patterns in magnetic rocks, especially those found in the ocean floor. This is where we can find these magnetic rocks, in ridges, coming from the outer core of the earth.
- 14. One famous example is the Mid-Atlantic Ridge found between South America and Africa.
- 15. An Evidence 04 Magnetic reversal as an evidence to Seafloor Spreading Theory
- 16. Since this change in polarity occurs, it allows scientists to visualize magnetic stripes in the ocean floor and construct a magnetic polarity time scale. Magnetic Polarity Time Scale
- 17. CREDITS: This presentation template was created by Slidesgo, and includes icons by Flaticon and infographics & images by Freepik Credits to different sources and Slidesgo! THANKS! Have a great day! Keep Learning!