Geologic Time The Rock and Fossil Record Geologic
- Slides: 44
Geologic Time The Rock and Fossil Record
Geologic Time Scale n n time divisions Geologists use different ________ to keep track of Earth’s history. These divisions are based on: q q n life forms present during the time Type of ______ period geologic changes occurring at the Type of ______ time. Geologic Time Scale – a record of Earth’s history, beginning 4. 6 bya, that shows events, time units, and ages.
Geologic Time Scale n There are three types of subdivisions of geologic time: q q q ERA – major subdivisions of time based on ______ differences in life-forms. Period _____ – subdivisions of eras based on types of life and geologic events (mountain building or plate movements). Epoch _____ – subdivisions of periods based on types of life and geologic events. (Epochs are found in the Cenozoic Era alone because the fossil records and rock layers are more complete for this time. )
Era Phane rozoic Eon Cenozoic Period Epoch Quaternary Recent Pleistocene Neogene Pliocene Miocene Paleogene Oligocene Eocene Paleocene Mesozoic Cretaceous Jurassic Triassic Paleozoic Permian Pennsylvanian Mississippian Devonian Silurian Ordovician Cambrian Precambrian Time
Earths Story and Those Who First Listened. n uniformitarianism to Scientists use __________ interpret the past and predict the future. q n James Hutton 1795 – “Theory of Earth” present past The _______ is the key to the _____. q Things that happened now must have happened in the past.
n n n Uniformitarianism versus Catastrophism– equal to slow change Uniformitarianism Catastrophism – equals quick sudden changes. Which is right? q A little of both.
Relative Dating - Superposition n n Here’s a stack of newspapers collecting dust in the living room. Everyday as the paper is read it is put in the pile. Someone comes to you and asks about an article from last week. Where do you look?
Relative Dating? Which came first? n Geologists use relative Which layer is older? dating to determine the ______ relative age of objects. Principle of Superposition – younger layers lie above older layers in an undisturbed sequence of C rocks. A n B A
The Principle of Superposition n In an undisturbed layer of rock the oldest rock BOTTOM and the youngest is is on the _______. TOP
The Principle of Superposition n Exceptions to the Principle include tectonic MOVE tilt, forces acting on the rocks to _______, ERODE fault, or _____ rock layers.
Original Horizontality: sedimentary layers are initially deposited in horizontal layers n The forces of reality beat up on the earth and break it into small pieces, which then wash down rivers to the ocean and settle out on the seafloor. In horizontal layers.
Relative Dating n Used by geologist to determine the order of events and the relative age of rocks by their POSITION in the stack. ______
Relative Dating n n This image shows a stack of rocks with 3 different types of rock and one fault. Which is the oldest?
Relative Dating n Here’s the sequence: A, B, fault, C C B B A
Unconformities n n Rock layers are a record of past geologic events. INCOMPLETE because they are Most are ______ missing layers. If sediment stops being deposited and EROSION goes to work removing material _____ then you will have a gap in the record. These gaps are called UNCONFORMITIES _________.
Angular Unconformities
Angular Unconformities
Angular Unconformities
Disconformity n No obvious evidence of missing rock layers UNEVEN surface caused by except for an _____ erosion.
Nonconformity When sedimentary rock layers form above METAMORPHIC IGNEOUS ______ or intrusive ______ rock layers. n The metamorphic or igneous rock is uplifted and eroded. n Sedimentary rocks are then deposited on top. n
Nonconformity Arrow points to contact of Cambrian Tapeats Sandstone on Precambrian Vishnu Schist.
Cross-cutting relationships: the OLDER thing being cut is ____ than the thing doing the cutting n n n You can’t cut it if it isn’t there. Igneous intrusions: Dikes, Sills, Batholiths, Laccoliths
Cross-cutting Relationships
Fossils
Fossils n Definition: q Fossil – the remains, imprints, or traces of onceliving organisms, usually preserved in rock, that tell us when, where, and how those organisms lived.
Fossils n n Fossils help scientists determine when and where plants and animals lived. Also, how they lived.
Fossil Formation n Necessary Conditions: q The body of a dead organism must be protected from scavengers and microorganisms. n Quick Burial (sediments from floods, landslides, ________ etc. ) Hard Parts ________ (bones, shells, or teeth) n Sedimentary Rocks _____________ Fossils typically do not n withstand the heat and pressure involved in forming igneous and metamorphic rocks. q Limestone, Shale, Sandstone are examples NEARLY ALL FOSSILS ARE FOUND IN SEDIMENTARY ROCK
Fossil in Virginia Appalachian Plateau Valley & Ridge Coastal Plain Why not the Blue Ridge and Piedmont?
Fossil in Virginia Era Period Epoch Cenozoic Quaternary Recent Pleistocene Tertiary Pliocene Miocene Oligocene Eocene Paleozoic, Mesozoic, and Cenozoic fossils are found in Virginia Paleocene Mesozoic Cretaceous Jurassic Triassic Paleozoic Permian Pennsylvanian 544 mya – present Paleozoic Mesozoic Cenozoic Mississippian Devonian Silurian Ordovician Cambrian Precambrian Time
Petrified Remains n Some or all of the original materials in the remains have been replaced by minerals.
Carbonaceous Films n n n The tissues of most organisms are made of compounds that contain carbon. Sometimes that’s all that is left. Pressure and heat force gases and liquids from the body and leave an outline of the body.
Carbonaceous Films n Swamps and deltas where large amounts of plant matter areas in which these fossils are found.
Molds and Casts n n n Seashells or other hard parts fall into soft sediment such as mud and get buried. Compaction and sedimentation turn the sediments to rock. Pores in the rock let water and air reach the object and allow it to decay. The resulting void is called a mold. Other sediments may fill the mold and solidify into a cast.
Original Remains n n Sometimes the original remains are preserved. Insects trapped in amber (crystallized resin) Ice men, mammoths Tar Pits
Trace Fossils n n n Fossilized tracks or other evidence of animal activity. Dino-tracks Coprolites
Index fossils n n n Species inhabit Earth for a period of time before evolving into new species or dying out. Paleontologists use animals that exist for a short time period as index fossils. Index fossil – species that existed on Earth for a relatively ______ short period of time, were ___________ numerous wide-spread geographically.
Index fossils n Index fossils are used to determine the age of rock layers. 200 Life Span (mya) A 500 - 200 B 400 - 200 C 400 - 300 400 500
Fossils and Ancient Environments n n environment Fossils also indicate the _______of an area long ago. Remember Antarctic rocks contain fossils of tropical plants
Fossils and Ancient Environments n n Most VA fossils are of _________ marine organisms Brachiopod fossils indicate a shallow sea environment. Brach’s are found in the mountains of Virginia What can you conclude from this?
Absolute Dating n n numerical Absolute time places a _______ age on an event. Radioactive decay is used to determine _________ the absolute age of rocks.
Radiometric Dating n n Radiometric Dating – determining the age of a material by comparing the ratio of the ______ (undecayed) material to the parent daughter ______ (decayed) material. Example: A rock has an isotope that takes 10, 000 years to decay into half of the parent material. The half-live is 10, 000 years. Scientist examine the rock and find exactly half of the material is “parent” material and half is “daughter” material. Then the age of 10, 000 the rock has to be ________ years.
C
- Compare geologic time with the geologic column.
- Sedimentary rock song
- Section 17-1 the fossil record
- How are fossils evidence for evolution
- Fossil record defintion
- What is the “fossil record”?
- What is absolute age?
- Fossil record definition biology
- Fossil record
- Darwin viewed the fossil record as
- Earth’s history and geologic time graphic organizer
- Match the letter
- How is the geologic time scale organized
- How is the geologic time scale organized
- Geologic time scale animals
- Fossils
- The longest subdivision of the geologic time scale is the
- A trip through geologic time answer key
- 4 divisions of geologic time
- Geologic time scale drawing
- Geologic time scale
- Time scale
- Amantz
- Silurian period
- Geologic time scale
- What is the longest subdivision in geologic time
- Geologic time scale drawing
- Chapter 12 geologic time
- Anecdotal record vs running record
- Chapter 3 standardized test practice answers
- A rock climber's shoe loosens a rock and her climbing buddy
- For minutes. start.
- Rock cycle sedimentary
- Igneous metamorphic and sedimentary
- Rock climb
- Easy rock cycle
- Daily time record system
- Record time
- Asset master
- Geologic sequestration
- Definition of geologic history
- Geologic column definition
- Pilot knob volcano
- Principle of superposition
- Disconformity