Geologic History Powerpoint Notes
Upcoming SlideShare
Loading in...5

Geologic History Powerpoint Notes



Adapted from serveral other powerpoints by Mr. Craig McKee, Mr. Greg Izzo and others

Adapted from serveral other powerpoints by Mr. Craig McKee, Mr. Greg Izzo and others



Total Views
Views on SlideShare
Embed Views



7 Embeds 125 75 20 18 8 2 1 1



Upload Details

Uploaded via as Microsoft PowerPoint

Usage Rights

© All Rights Reserved

Report content

Flagged as inappropriate Flag as inappropriate
Flag as inappropriate

Select your reason for flagging this presentation as inappropriate.

  • Full Name Full Name Comment goes here.
    Are you sure you want to
    Your message goes here
Post Comment
Edit your comment
  • Click to see arrows shoot in one at a time. #1= included fragments #2=intrusion, cross-cutting #3= angular unconformity #4=erosion. This is the outcome of the next slide.
  • Sediments deposited, sea-level lowered, layers intruded, layers tilted, erosion and deposition under sea, sea-level lowered again. Click arrow to continue.
  • Click to see arrows shoot in one at a time. #1= included fragments #2=intrusion, cross-cutting #3= angular unconformity #4=erosion. This is the outcome of the next slide.
  • Sediments deposited, sea-level lowered, layers intruded, layers tilted, erosion and deposition under sea, sea-level lowered again. Click arrow to continue.
  • Click to see arrows shoot in one at a time. #1= included fragments #2=intrusion, cross-cutting #3= angular unconformity #4=erosion. This is the outcome of the next slide.
  • Sediments deposited, sea-level lowered, layers intruded, layers tilted, erosion and deposition under sea, sea-level lowered again. Click arrow to continue.

Geologic History Powerpoint Notes Geologic History Powerpoint Notes Presentation Transcript

  • Interpreting Geologic History
  • If the history of our planet was condensed to only one year , when would the “important” events in our history have taken place? Earth’s History in One Year
    • Reminder add about early earth formation
    View slide
  •   View slide
  • January to March
    • One quarter (1/4) of the year was over, and no life was present. The environment was extremely chaotic.Barren mountains dominated until the oceans formed in late March.
  • April to November
    • April Fool’s Day = first life on Earth!
    • Only single-cell organisms near thermal vents and in warm oceans.
    • Multi-cell organisms sprout up towards the end of August!
    • These types of life dominate all the way until December!
  • December
    • December 2 nd – the first hard shelled organisms (trilobites).
    • December 3 rd – more complicated sea-creatures begin to show up.
  • December 6 th
    • 60% of North America is covered by water!
    • Endless torrential rain and huge amount of erosion over continents.
  • December 7 th
    • FINALLY, plants are able to make their way onto land.
    • Many are washed away by the torrential rain, but some are able to grab hold and latch on.
  • December 10 th
    • Where are all the people??? Still nowhere to be found!
    • Fish are thriving in the oceans.
    • Some grow feet, walk onto land, and call themselves Amphibians.
    • First land-only animals are on their way.
  • December 17 th
    • Look out for the insects!
    • At the end of the month, Jurassic Park opens up. Dinosaurs begin their reign on land.
  • December 20 th
    • The Appalachian Mountains stand taller than any other mountain chain on the continent! They later shrunk in their old age.
    • Dinosaurs are chasing the first mammals around, enjoying snack-time.
  • It’s snack time!!! AHHH!!!
  • December 24 th
    • An asteroid the size of Manhattan slams into the Yucatan Peninsula. The dinosaurs’ “one week” of dominance ends. The mammals are more than excited to see them go.
    • At the end of the day, the Rocky Mountains start to form.
  • December 25 th
    • Here’s where the action kicks up!
    • Mammals are running around without having to worry about their buddy T-Rex.
    • The Mammal Baby-Boom begins.
  • December 28 th
    • The Colorado River begins to cut through the land below it. A few days later, the Grand Canyon is about a mile deep.
  • December 31 st
    • Where are all of the humans? During the morning and afternoon, there is still no sign of them.
    • At around 10 PM, early human ancestors appear.
    • Between 10 and 11 PM, massive ice sheets will advance and retreat over North America and Eurasia FOUR times.
  • The Last Hour on December 31 st
    • Neanderthals show up to the New Year’s party.
    • With a half hour left before the end of the year, cavemen make drawings on the walls.
    • With fifteen minutes left, homo sapiens make the first weapons – spears and knives.
    • Civilizations appear in the last five minutes: Egyptians, Greeks and Romans each spend one minute building and destroying their empires.
  • The Last Minute of the Year!
    • With 3 seconds left in the countdown, Columbus stumbles into the Americas.
  • The Last Minute of the Year!
    • The Industrial Revolution began just one second before the New Year.
  • The Last Second of the Year!
    • Within the last 5 tenths (0.5) of a second, humans invented cars, planes, computers, TV, cell phones, and nuclear weapons.
  • What Will the New Year Bring?
  • Welcome Back! Please complete the pre-test when you come in!
  • The Grand Canyon, AZ Geologic History A Journey Through Time Please take out your Earth's History Notes Packet
  • Geologic History Intro and Relative Dating Absolute Dating Fossils & Rock Correlations Geologic Time Life and Evolution “Do Now’s” and HW
  • Who’s Younger? How Do You Know??
  • “ in a Nutshell” Geologic History of the Earth
  • Origins of our Solar System Video Clip
    • Earth formed through the gravitational attraction and accumulation of asteroids and rocky debris
    • This accretion of material generated a tremendous heat causing the planet to be molten
    • The denser materials settled into the interior and the Earth’s layered internal structure formed.
    Earth’s Formation
  • Creation of the Earth
  • Earth's first atmosphere 4.6 billion years ago was most likely comprised of hydrogen and helium (two most abundant gases found in the universe!) Through the process of outgassing, the outpouring of gases from the earth's interior, many other gases were injected into the atmosphere. These include: water vapor (produced rain - rivers, lakes, oceans) carbon dioxidenitrogenAs outgassing occurred over a period of millions of years, the atmosphere evolved to its current state
  • Life and Evolution Diverse Ordovician Sea-Life Video Clip
    • Evidence from the fossil record (preserved in sedimentary rocks) shows that a wide variety of life forms have lived in Earth’s changing environments over time.
    Variations in Fossils and Environments
    • The comparisons of fossil remains and current life forms enable scientists to make predictions about the Earth’s past environment.
    • A major reason for changes in Earth’s environment over geologic time has been the movements of plates and their associated landmasses.
    Variations in Fossils and Environments
    • The theory of organic evolution states that life forms change through time.
    • As environmental conditions change, variations within a species give certain individuals a greater chance for surviving and reproducing .
    Fossils and the Evolution of Life
    • These variations, along with others get passed on to future generation leading to the creation of a new species .
    • The fossil record provides evidence for the theory of organic evolution.
    • This also shows that evolution does not always occur at the same rate .
    • There are times of rapid extinctions and subsequently rapid evolution of new species.
    Rates of Evolution
    • An impact event , such as the collision of a comet or asteroid with Earth, may cause catastrophic environmental changes leading to rapid extinctions and evolutions.
    • Such an event probable occurred at 65 m.y. and is associated with a massive extinction of roughly 70% of the Earth’s species.
    Rates of Evolution
    • Precambrian (4.6 b.y - 544 m.y.)
      • Simple organisms (invertebrates)
      • “ Soft-Bodied” Organisms (Fossils are rare)
    Life On Earth Throughout Geologic Time
  • Stromatolites Formed from the trapping of sediment in layers by Blue-Green Algae (Cyanobacteria)
    • Paleozoic (544 – 251 m.y.a.)
      • Organisms proliferate and become more complex ( vertebrates )
      • Shelled (mineralized skeletons and shells) organisms develop
      • (Brachiopods/Trilobites)
      • Amphibians develop from lobe-finned fish
      • Era ends with a mass extinction killing off more than 95% of the life on earth
    Life On Earth Throughout Geologic Time
  • Cambrian Life
  • Silurian Life
  • Eurypterid (Sea Scorpion) Fossil Largest fossil with human for scale
  • Eurypterid in Action
  • Devonian Life
  • Phacops Trilobite of the Devonian
  • Carboniferous Forests – formed extensive coal deposits
  • Evolution of Amphibian from Lobe-Finned Fish (Devonian)
    • Mesozoic Life (245-65 m.y.a.)
      • “ Age of Reptiles ” (dinosaurs, flying reptiles and birds develop)
      • Modern animals and plants begins to develop on land
      • Era ends with a mass extinction killing off dinosaurs, ammonoids, flying reptiles, and some swimming reptiles.
    Life On Earth Throughout Geologic Time
  • Triassic Plateosaurs
  • Iguanodons
  • Cretaceous T-Rex
  • Impact Event
    • Cenozoic Life ( 65 m.y.a. – present)
      • “ Age of Mammals ” (mammals begin to develop and evolve)
      • Humans develop from primates (Homo Habilus 1.6 m.y.)
    Life On Earth Throughout Geologic Time
  • Early Hominids Mastodonts
  • ESRT, p. 8-9
    • Scientists have determined the age of the Earth to be about 4.6 billion years old.
    • 4,600, 000, 000 years = 4.6 x 10 9 years (scientific notations you should know)
        • 10 9 = billion
        • 10 6 = million
        • 10 3 = thousand
        • 10 12 = trillion
    How old is the Earth? For example, 10 9 can be read as “one with 9 zeroes after it” OR 1,000,000,000
    • Began in the late 1700’s when James Hutton published his Theory of the Earth.
    • In this work he was the first scientist to argue effectively that geologic processes proceed over long spans of time
    Birth of Modern Geology
    • The physical, chemical, and biological processes that operate today have also operated in the geologic past.
    • “ The present is the key to the past”
    Principle of Uniformitarianism Hutton's Major Contribution
    • Geologists can infer events of the past by
    Looking at features of rocks and rock outcrops
  • Uniformitarianism (Principle of
    • states that the forces that acted upon the
    • ___________ crust…
    Uniformity) Earth’s
    • in the __________ are the same as those that are ____________
    • today.
    past active ** THE KEY TO THE PAST IS THE PRESENT**
  • Relative Dating Techniques
    • Prior to the discovery of radioactivity, geologists had no reliable method of giving specific dates to geologic events and had to rely on relative dating techniques.
    • Relative Dating means placing rocks or events in their proper sequence of formation, based on a comparison to other rocks
    Relative Dating
  • 5 Basic Laws:
    • 1. Law of Original Horizontality
    • 2. Law of Superposition
    • 3. Law of Inclusions
    • 4. Law of Cross-Cutting Relationships
    • 5. Law of Original Lateral Continuity
  • Law of Original Horizontality
    • Strata is originally
    • deposited in flat horizontal layers because sedimentary particles settle from air and water under the influence of gravity
  • Law of Original Horizontality
    • If strata are ___________, then they must have suffered some kind of disturbance after they were deposited.
    Grand Canyon Western Iran Steeply Inclined
    • Principle of Original Horizontality states that sediments are deposited in horizontal layers
    Layer 1 – Siltstone Layer 2 – Limestone Layer 3 – Sandstone Relative Dating Laws
  • What has happened to this rock strata?
  • Did it happen before or after the rock had formed? What has happened to this rock strata?
    • the principle that the _________ layers in a sequence of rock strata must have been deposited __________ the layers above, unless the rock strata have been ___________ or___________
    bottom before disturbed uplifted
    • The _______ rocks are found at the bottom.
    • Geologists can date the
    • _________ ages of the strata from
    • ________ to __________
    older relative oldest youngest
  • oldest youngest
  • Law of Superposition
    • Therefore the order of deposition is from the bottom upward.
    • Law of Superposition states that in an undeformed sequence of strata, each bed is older than the one above it and younger than the one below it.
    Relative Dating Laws
  • Younger  Older   Oldest
  • Grand Canyon, Sequence of Strata Oldest Youngest Which rock unit is the youngest? oldest?
  • Grand Canyon, Sequence of Strata
  • Older Younger Sheep Rock, Central OR
  • Law of Inclusions
    • A rock must first exist in order to be weathered, deposited and cemented as a _____ in another rock. Therefore…
    • If rock is composed of _____________, the rock fragments must be ___________ than the rock in which they are found.
    fragments older
  • Law of Inclusions Which is older the Granite or the Sandstone? In figure A? In figure B? Sandstone is older Granite is older
  • What's the oldest part of this rock? Youngest?
    • The law of inclusions also applies to fossils preserved in the bedrock.
    • _________ are any naturally preserved remains or impressions of living things.
    • They are found in _______________ because
    • _____________________
    • ____________
    Sedimentary rock Heat & pressure in igneous and metamorphic rock destroys them
  • ESRT pp. 8-9
    • Spiral shell
    • Lower Cambrian to present day
    • Foot-like muscle used to move
    • Environment:
    • Land, Fresh Water, Marine
    • Present day example: a snail
    • Fed on algae
    Gastropods Worthenia
    • Varying shell shapes, not spiral
    • Lower Cambrian to present day
    • Attached themselves to rocks
    • Symmetrical
    • Environment: Benthic Marine
    • Filter feeders
    Mucospirifer Brachiopods
    • Of the Phylum Arthropod
    • Lower Cambrian to Late Permian
    • Marine Benthic
    • Some were believed to consume mud, filter feed or scavenge
    Trilobites Phacops
    • Squid-like creatures with shells. Swam with water propulsion. Predators had beaks
    • Chambers separated with sutures
    • Nautiloids lived from the Cambrian to present day
    • Ammonoids lived from the Triassic to the Cretaceous
    Nautiloids and Ammonoids
    • Colonial or solitary animals, not plants!
    • Captures small prey with stinging cells
    • Live in shallow marine water Benthic
    • Ex. Horn Coral (solitary)
    • Lived from the Cambrian to present day
    Cnidaria (Corals)
    • Lobster like creatures
    • Late Ordovician through Devonian
    • Sea scorpions (Predators)
    • Belong to the phylum Arthropoda (the same as Trilobites)
    • Marine, land, and fresh water
    • Length could reach up to 2 meters long
    Eurypterids NYS Fossil
    • Planktonic (floated around)
    • Often good index fossils since they are found all over the world for a short period of time, in great numbers.Mid Cambrian Devonian Probably filter fed Once believed to be shark teeth
    • “ Sea Lillies”
    • Late Ordovician to present day
    • Normally the stems are found
    • Benthic Marine
    • Filter feed
    • Not always symmetrical
    • Burrowers
    • Mud Eaters Benthic
    • Marine or Fresh water
    • Of the Phylum Molluska
    • Cambrian to Present day
    • Ex. Clams, mussels, scallops
  • Unconformity
    • Buried erosional surfaces that are preserved in the rock record.Create “gaps” in the geologic rock record
  • Rock Fragments (or Inclusions) that are contained in another rock are older than the rocks in which they are found Unconformity
  • Law of Cross-Cutting Relationships
    • Any __________ or ______, must be younger than all rocks through which it cuts. Simply put, the body of rock that is cross-cut had to be there first in order to be cut by an intruding igneous body or fault.
    Igneous rock fault
    • In general rock is always_________ than the process that changed it.
  • Some Processes Include:
    • folds
    • faults
    • tilts
    • intrusions
    • extrusions
    • Intrusions are younger than the rocks that they intrude
    • Faults (or cracks) are younger than the
    • rocks that they cut through
    • Extrusions are younger than the rocks they form above
    Principle of Cross-Cutting Relationships
  • Fault Fold Principle of Cross-Cutting Relationships
  • How does the age of the fault compare to the age of the rock layers?
  • Folded Rock Strata
  • How does the age of the crack compare to the age of the rock?
  • Principle of Cross-Cutting Relationships
  • Sedimentary layers (the law of original horizontality)
  • Sedimentary layers
  • Sedimentary layers
  • Sedimentary layers
  • Sedimentary layers
  • The fault came after the rock was formed
  • Sedimentary layers The tilt came after the the rock was formed
  • The extrusion came after the rock was formed 1 2 3 4 5 Contact metamorphism
  • 1 2 3 4 5 6 The extrusion came after the lower layers were formed but…. Before the top layer
  • 1 2 3 4 5 This intrusion came after all the layers
    • These changes can lead to exceptions to the Law of Superposition:
    • a.An __________ is
    • an igneous rock that formed from lava on the surface of the crust.
    • An __________ must be younger than the strata below it, but ________ than any layers above.
    extrusion older
    • b. __________ are created when molten rock (________) is injected into older rock layers in the crust.
    intrusions magma
    • _____________ are
    • _____________ than
    • all the rock layers in contact with them.
    Intrusions younger
    • c. _______ are bends
    • in the rock strata. ________ can overturn rock strata so that ________ rock lies on top of _________ rock.
    Folds folding older younger
    • d. _______ are cracks
    • in rock strata.
    • _______ produce offset layers.
    Faults Faults
    • d. _______ are cracks
    • in rock strata.
    • _______ produce offset layers.
    Faults Faults
    • Rock strata must be
    • ________ than the process that changed it.
    • _________, ________ and ________ ___________
    • are features created after rock or sediment has been deposited.
    cracks veins natural cement
  • The following diagram represents a cross-sectional view of a portion of Earth’s crust. What is the relative age of the igneous rock? The igneous rock is older than the … The igneous rock is younger than the …
  • Law of Original Lateral Continuity
    • . When sediment is dumped by an agent of erosion, strata extends from the source until it gradually thins to zero, or until it reaches the edges of the basin of __________.
  • Folding of strata (rock layers) over upon itself Possible Exceptions to the Law of Superposition
  • Strata is displaced by a Fault ( Thrust Fault ) Possible Exceptions to the Law of Superposition
  • Law of Original Lateral Continuity
  • Law of Original Lateral Continuity
    • This concept enables us to correlate outcrops of strata that has been dissected by processes of ________.
  • Let’s follow the progression of geological events that formed the sequence below.
  • Step One Deposition of rock units A-E
  • Step Two Area is uplifted, and is intruded by rock unit D (Sill)
  • Step Three Intrusion of rock unit F (Dike)
  • Step Four The rock sequence is tilted and then eroded, setting the stage for an angular unconformity
  • Step Five Area subsides, followed by the deposition of rock units G-K
  • Step Six Area is uplifted and the upper surface begins to undergo erosion
  • That is the story behind this rock sequence
  • Fossils & Rock Correlations
    • Correlation is
    Matching similar rock strata at different locations to see if they formed at the same time
    • Correlation is the process of matching rock units or events in separate rock formations
    • Correlation of rock units and geologic events can be based upon continuity, similar rock composition, fossil evidence, and volcanic markers .
    Rock Correlation
    • Correlation by:
      • Continuity – “ walking the outcrop ”; performed by following a rock layer for great distances
      • Similarities in rock composition and texture can be used to match rocks over large areas
  • Grand Canyon Stratigraphy
    • Fossils can be used to help match separate rock layers
    Unconformity Fossil Evidence and Rock Correlation
  • Correlation using Index Fossils
  • Ways to correlate rock formations:
    • “ Walking the outcrop”
    • is done by
    Walking from end to end
    • This is correlation by
  • You can match the rock strata in one location with rock strata in more distant locations by Comparing , c o l o r texture composition sequence of layers
  • Time correlation compares ____________ contained in the rock strata index fossils 1 2 3 4 4 5 6 3
  • The best index fossils:
    • a. _________________
    • b. _________________
    Exist for a brief period of time are widespread
  • Which fossil would make the best index fossil? Found in only 1 layer (short lived) Found in all samples (widespread)
  • Another way of correlating layers by time is through ___________________ Volcanic ash falls
  • These ash falls are very ________ events. A single layer of ______ can be found over a large area, this allows geologists to make a__________________ from one location to another at the position of a common ash fall. brief ash time correlation
  • Volcanic Eruptions and Rock Correlation
    • Violent volcanic eruptions can emit large quantities of volcanic ash
    • The ash can spread out over a large area of land, creating an excellent geologic marker for rock correlation
  • Rock Correlation Activity
  • Rock Correlation Activity
    • A. Geologists noticed that rock _________ can be identified by the fossils they contained.
    • They also found that certain __________ were consistently located ________ or _________ other formations.
    formations above below
    • From these observations they established a
    • ______ ____ ______
    • with a sequence of fossil groups from ______ to
    • ______________
    relative time scale oldest youngest
    • Each of these groups was named for a location where its ____________ ______ could be observed in the rocks.
    Characteristic fossil Example: Devon fossil “ Devonian ” found in Devon England
    • Further observations from around the world established a
    • ________ _____ _____
    Geologic time scale
    • Based on __________________________________
    • and ________________
    • ________ _____ _____
    Inferred positions of Earth’s Landmasses Major Geologic Events (ex. Ice ages & Orogenys)
    • The study of geologic time allows us to reconstruct Earth’s history, gaining a sense of the world before humans and allows us to possibly predict events and conditions of the future.
    Geologic Time
    • An ________ is the process of mountain building
    • _________ causes gaps in the geologic record.
    • When a new layer
    • of rock is laid down on a surface that has been _______ it forms a buried erosional surface or an
    • ___________________
    Eroded, unconformity
  • Who’s Younger? How Do You Know??
  • Relative vs. Absolute Dating
    • Five family members’ ages are compared:
    • Anthony is the youngest.
    • Melanie is 4 years old.
    • Michael is older than Susan.
    • Susan is 16 years old.
    • Ashley is older than Melanie, but younger than Susan.
    • Give the order of the family members from oldest to youngest. Also, which descriptions give relative ages and which give absolute ages?
    Michael Susan Ashley Melanie Anthony
    • Age of rock or geological event in years before the present ( as opposed to relative ages ).
    • Common units are:
        • millions of years ago = m.y. = 10 6
        • billions of years ago = b.y. = 10 9
    • How do scientists find absolute ages?
  • What were some of the techniques used to determine absolute time prior to the discovery of radioactivity. Tree Rings Varves
    • Modern science now uses Radioactive Isotopes to find the absolute age of a given material (rock, fossil, etc.).
    Modern Absolute Dating Techniques
  • Mass spectrometer – instrument used in the detection and study of isotopes
    • A. Fossils enabled geologists to give ___________ time,
  • Relative Time
    • Compares rock ages to _______________.
    • Ex: The Limestone is older than the Sandstone.
    each other
  • However,
    • B . Measurements of natural ___________in ( metamorphic and igneous) rocks have allowed the _________ time scale to be an ________ time scale.
    geologic absolute radioactivity
    • The _________ _____ of an object is measured in years.
    • Ex: The limestone formed 5 mya and the sandstone formed 2 mya
    absolute age
    • C. Chemical elements often have several forms called _______________
    • Let’s review some basic chemistry so that we can obtain a better understanding of this technique.
    Modern Absolute Dating Techniques
  • Let’s review the structure of an atom The basic building block of matter Basic Chemistry Review
    • An element is a substance consisting of atoms that are chemically alike (# of protons).
    • Most elements exist in several different types of isotopes (atoms with a different number of neutrons in their nuclei).
    • Examples: Carbon isotopes, C-12 & C-14
    Basic Chemistry Review
    • The nucleus (containing neutrons and protons) of radioactive isotopes are unstable and over time they will emit particles and electromagnetic energy.
    • This is known as Radioactive Decay , and changes the radioactive isotope into other isotopes or atoms. This occurs until, a stable isotope forms.
    Basic Chemistry Review
    • The rate of decay (breakdown) for any radioactive isotope is constant .
    • Over a given period of time, a definite fraction of the atoms of an isotope will decay .
    How can we use radioactive elements to date things?
  • ISOTOPE: An unstable element with different number of neutrons than a normal (stable) element. (Its unstable so wants to change to stable)
  • EX. C C 6 6 12 14 6 protons 6 protons 6 neutrons Unstable 8 neutrons
  • EX. C C 6 6 12 14 6 protons 6 protons 6 neutrons 8 neutrons unstable
  • D. If the nucleus has more or fewer than the normal number of ____________, the isotope may be ____________ neutrons radioactive (unstable)
    • E. A radioactive isotope will break down naturally into a lighter element called
    • _____ ________ which is stable.
    decay product
  • This process is called… Radioactive Decay
    • F. A sample starts out at “Time zero” with _______ Percent of radioactive material.
    • Time Zero: when the sample is originally formed by cooling or solidification of igneous or metamorphic rock
    • As time goes by and the sample gets older, the radioactive element decay, and _______ radioactive atoms remain in the sample.
    • Therefore, the higher the ratio of decay product to the radioactive element, the _____ the sample.
    • The ratio between the mass of the radioactive element and its decay product in a sample is the _______________
    decay product ratio
    • G. The decay of the parent atoms in a sample to daughter atoms is a _________ process…
    • That happens at _____________ rates for different radioactive elements. Lets model this with pennies…
    • H. The rate of decay of a radioactive element is measured by its’ _______ _________
    half life
  • Original=100% Decay product=0% 100/0 Or 1 to 0
  • Original=50% Decay product=50% 50/50 Or 1 to 1 After one Half-life:
  • Original=25% Decay product=75% 25/75 Or 1:3 After two Half-lives:
  • Original=12.5% Decay product=87.5% 12.5/87.5 After three Half-lives:
  • Original=6.25% Decay product=93.75% 6.25/93.75 After four Half-lives:
    • The time required for half of the atoms in a given mass of an isotope to decay is known as the half-life of the isotope.
    • Each radioactive isotope has its own characteristic half-life, which is not affected by any environmental factors (T o , P, or chemical reactions), mass or volume .
    • The method of using the half-life of a radioactive isotope to determine the absolute age of a material.
    • The ratio between the amount of the original isotope ( Parent Material ) and the amount of its decaying product ( Daughter Product ), is used to establish the absolute age of a sample.
    Radioactive Dating
  • “ Daughter Product” “ Parent Material”
  • Carbon Dating 0 Half-Life Key Other C 14 N 14
  • Carbon Dating 1 Half-Life (5,700 years) Key Other C 14 N 14
  • Carbon Dating 2 Half-Lives (11,400 years) Key Other C 14 N 14
  • Carbon Dating 3 Half-Lives (17,100 years) Key Other C 14 N 14
  • Carbon Dating 4 Half-Lives (22,800 years) Key Other C 14 N 14
  • Carbon Dating 5 Half-Lives (28,500 years) Key Other C 14 N 14
  • Carbon Dating 5 Half-Lives (28,500 years) Key Other C 14 N 14
  • (ESRT, pg. 1) Which isotope has the shortest half life? Longest?
  • 1/16 1/32 1/64 22,800 28,500 34,200 Old REGENTS Questions
  • Do Now How many Potassium-40 half lives have passed if there are 3 times more Argon-40 atoms than Potassium-40 atoms? What if there are 3 times as many Potassium-40 atoms?
    • Igneous and metamorphic rocks work excellent for radioactive dating because at the time of crystallization (or recrystallization), a specific ratio of stable and radioactive isotopes are incorporated into the crystals.
    • On the other hand, sedimentary (clastic) rocks do not work well because they are composed of older, pre-existing rock fragments.
    Can all rocks be dated using this technique?
    • Imagine a rock forms with zircon mineral grains containing U 238 and no Pb 206 .
    • Basic Facts on this Isotope
    • Half Life of Uranium-238 (U 238 ) = 4.5 * 10 9 yr
    • U 238 decays to become Lead-206 (Pb 206 )
    How does this Technique Work?
  • Decay of U-238 If this rock were to be found today, and contained a 1:1 ratio, equal quantities of both U 238 to Pb 206 , it would be concluded that the rock formed 4.5 b.y. How old would the sample be if it had a 1:3 ratio of U-238 to Pb-206?
    • Radioactive isotopes with very long half-lives are excellent for dating very old rocks, but for younger objects, isotopes with shorter half-lives are better at the finding absolute age.
    • One such isotope is Carbon-14 (C 14 ), with a half-life of 5,700 years.
    Using Different Isotopes for Different Studies
  • Carbon-14 (C 14 )
    • Carbon-14 dating – also called radiocarbon dating – can be used to date remains that contain carbon up to 70,000 years old.
    • This method has been used to date early humans, mastodonts, and many other geologically “recent” organic remains.
  • Let’s examine the breakdown of Carbon-14
  • N 14 Ar 40 Pb 206 Sr 87 5.7 x 10 3 1.3 x 10 9 4.5 x 10 9 4.9 x 10 10 Element Decay Product Half-life
    • “ Time Zero” for carbon dating begins when the organism ___________ or when the ________ burns out.
    dies wood fire
    • H. Calculating the age of a rock:
    • 1. What would be the age of the rock if it has equal amounts of C-14 and its decay product N-14?
  • One half life has gone by
    • 5.7 x 10 3 years
    • or 5,700 years
    • 2.What % of the sample is radioactive after the following half-lives,
    • 1 half-life
    • 2 half-lives
    • 3 half-lives
    50% 25% 12.5%
    • 3. After 11,200 years how much C-14 would remain in a 10 gram sample?
    25% or 2.5 grams 1/4 of the original amount
  • I. Selecting the Best Radioactive Element:
    • 1. Under 50,000 years
    • 2. Over 50,000 years
    Use Carbon-14 Use Uranium-238
    • Carbon 14 is used for dating
    • organic material
    • And ancient wood fires
  • State the best isotope to use to discover the age of the individual “caught off guard” in the cartoon below. Why?
  • DO NOW Please pick up a copy of the Absolute Dating Lab!
  • Do Now’s
  • The following diagram represents a cross-sectional view of a portion of Earth’s crust showing sedimentary rock layers that have not been overturned. The letters identify the specific layers. Which rock layer is the oldest? Youngest? DO NOW
  • What is represented by line A-B?
  • List the rock layers from oldest to youngest. A D C E B B A, D, C, E, B Do Now Take out your HW!!!
  • C D E B A G F H I Dating the Lunar Surface
  • C D E A H I G F B
  • Do we remember this stuff... What is the evidence that indicates the fault is the most recent geologic event to have occurred in this area?
  • What is the evidence that indicates rock layer B is younger than layers A and C? Earth Science Review Concepts
  • How does the age of the igneous intrusion [B] compare with the age of the shale [F]?
  • The most apparent buried erosional surface is found between which rock units?
  • E D B A C Can you figure this out?
    • What is the definition of a half life?
    • Of the radioactive isotopes listed on the front of the ESRT, which one has the longest half life?
    The time required for half of the atoms in a given mass of a radioactive isotope to decay Rubidium-87 Spend a moment and look this up...
  • Do Now Which letter (A,B,C) represents one half-life?
  • Do Now How much time is represented by letter B?
  • Take out your HW
  • Do Now Which isotope (A, B, C, D) has the shortest half-life?
  • Do Now Which isotope is represented by line B? (use your ESRT, p. 1)
  • Do Now Take out your HW
  • DO NOW Please take out your Absolute Dating Lab
  • Do Now Clear your desks and get ready for the Quest!!!
  • Decay and Growth Curve of Isotopes Take out your HW! Notes Packet, p. 13 - Radon decays into radioactive solids - Half -Life of 4.5 days - Generated during the decay of Uranium - Inhalation of Radon or decay products may cause lung cancer Radon Facts
  • Explain how radioactive isotopes are used to find the absolute age of a rock, bone, fossil?
  • State the name of the isotopes in the graph.
  • Which rock layer is the oldest?
  • Which is older, rock layer F or rock layer D?
  • What is an unconformity?
    • Review Book
    • Multiple Choice Problems
    Take out your HW
    • 1
    • 2
    • 3
    • 3
    • 1
    • 2
    • 3
    • 1
    9. 4 10. 3 11. 1 12. 3 13. 2 14. 4 15. 4
  • Take out your Marsium Lab DO NOW 1 half-life Sample Data
  • Which rock layer is the oldest? _______ _____
  • What evidence suggests that rock layer D is older than layer C?
  • Which is older, rock layer F or rock layer D?
  • E D B A C State the age of the rocks in order from oldest to youngest.
  • How does the age of the igneous intrusion [B] compare with the age of the shale [F]?
  • What is represented by line A-B?
  • What is an unconformity?
  • What evidence indicates that an unconformity exists between layers A and B?
  • The most apparent buried erosional surface is found between which rock units?
  • Explain why radioactive isotopes are used to find the absolute age of a rock, bone, fossil? _______ _____
  • How many half-lives are represented by letter A, B, & C?
  • State the name of the isotopes in the graph.
  • Which isotopes are represented by the following graphs (A, B, C)? A B C
  • Ms. Gill’s Baby Picture Clear your desks and get ready for the Quest!!!
  • What is the story here? 1
  • What is the story here? 2
  • What is the story here? 3
  • What is the story here? 4
  • What is the story here? 5
  • What is the story here? 6
  • What is the story here? 7
  • What is the story here? 8
  • What is the story here? 9
  • What is the story here? 10
  • What is the story here? 11
  • What are the rules for reading rock layers?
    • Superposition
    • Cross-Cutting Relationships
    • Unconformities
    • Contact Metamorphism
    • Uniformity of Process
  • Thanks to the collective resources of ESPRIT for contributing images Design via Threadless
  • Practice: what happened here?
  • Practice: what happened here?
  • Practice: what happened here?
  • Practice Geologic Profiles Look at the geologic profiles, write down what you think is the correct sequence of events. Then click the mouse to advance the presentation. Repeat this process for each of the profiles.
  • Profile 1
    • Ss with fish
    • Ls
    • Ss
    • Sh
    • Ls
    Sequence of Events Remember the law of superposition. Oldest Youngest
  • Profile 2
    • Ss
    • Ls
    • Cngl
    • Sh
    • Faulting
    • Ss
    Sequence of Events Faults are younger than the rock they are in. How do you know there is a fault? Look for the same rock layers. They do not line up.
  • Profile 3
    • Ss with fish
    • Ls
    • Ss
    • Sh
    • Ls
    • Intrusion
    • Tilting, uplifting, erosion
    • Subsidence (sinking)
    • Cngl
    • Sh
    • Ss with fish
    • Ss
    • Ls
    • Sh
    Sequence of Events Do you know what this is? An unconformity! These two steps formed it. Remember this a buried erosional surface
  • Profile 4
    • Sh
    • Ss with fish
    • Cngl
    • Ls
    • Folding
    • Intrusion and Extrusion
    Sequence of Events Intrusions and extrusions are younger than the rock they are in. Metamorphic rock tells you whether you have an intrusion or an extrusion .
  • Profile 5
    • Sh
    • Ss
    • Cngl
    • Ss with fish
    • Ls
    • Intrusion
    • Uplifting
    Sequence of Events Magma was forced in between the existing layers of rock to create this formation. You know it is an intrusion because… Metamorphic rock is on all sides.
  • Exposed volcanic ash layers in Alaska provide an excellent unit for correlation and establishing ages for geologic units and events
  • Rock Correlation Activity Create a full sequence of strata from these four different outcrops.
  • Rock Correlation Activity
  • Rock Correlation Activity
  • What can you infer happened in this area based on these footprints (trace fossils)?
  • Geologic Timeline
    • What are the characteristics of a good index fossil? (You must know 2)
    • Explain why volcanic ash deposits make good index layers for rock correlation?
    Fossils of organisms that lived for a short period of time over a wide geographic area Volcanic ash deposits cover a large geographic area in a relatively short period of time You and your neighbor need to be able to complete these questions. Use your notes to help (p. 14-15)
  • _ __
  • _ __
  • _ __ Take out your HW Notes, p. 16-17
  • Take out a pencil, ESRT and calc. QUIZ TIME!
    • What is longer unit of time, a geologic era or a period?
    • What geologic period of time are we in today? Epoch?
    _ __ Take out your ESRT (p. 8-9) and complete the following questions with your neighbor... An Era is larger and they are broken up into Periods Quaternary Period, Holocene Epoch
  • Which geologic period ended with the extinction of many kinds of marine animals, including trilobites? Which orogeny was caused by the collision of North America and Africa along a transform margin creating Pangaea? The Permian Period The Appalachian (Alleghanian) Orogeny _ __ Use your ESRT to complete the following Questions
  • The Devonian aged siltstone shown in the photograph below occurs as surface bedrock in Hamilton, NY. What does the presence of the fossil suggest about the environment of Hamilton during the Devonian? _ __
  • Earth's History Notes Packet, p. 23
  • _ __ Use your ESRT [p. 8-9] to complete the following question
  • _ __ Mr. Gill's Baby Picture Please take out your ESRT
  • The table below gives information about the radioactive decay of carbon-14. Part of the table has been deliberately left blank for student use. After how many years will 1/128 of the original carbon-14 remain?
  • What is the correct order of development from the original (oldest) stage to the most recent (youngest) stage? DO NOW Work with a partner
  • Constructed Response Questions State one method used to correlate rock layers… State one piece of evidence why the limestone is the most resistant rock layer in the outcrops. Comparing rock texture / composition, looking for index fossils, examining sequencing of strata The limestone unit extends the furthest out of the outcrop (cliff)
  • Constructed Response Questions What does the discovery of Ordovician aged fossil corals in the surface bedrock of NYS cause you to infer? Parts of NYS were once in a shallow, warm marine envrionment