Earth’s History Test Review

Describe uniformitarianism

uniformitarianism Earth is constantly changing since its creation The same forces that changed earth’s surface millions of years ago, are changing it now What are those forces?

uniformitarianism Earth is constantly changing since its creation The same forces that changed earth’s surface millions of years ago, are changing it now What are those forces? Weathering, erosion, plate movement and resulting landforms and events (seafloor spreading, creation and destruction of crust, volcanoes, earthquakes, mountain building, creation of seas)

What is Continental Drift What evidence supports it?

Continental Drift Evidence http://www.britannica.com/science/continental-drift-geology/images-videos/A-discussion-of-some-of-the-evidence-supporting-continental-drift/182285 Matching fossils on separate continents Matching rock formations on separate continents Puzzle-like continent shapes Tropical fossils in arctic climates

Fern fossil found in Antarctica

Lithosphere= crust + upper mantle Asthenosphere= soft, weak layer of mantle (magma)

What is the difference between relative and absolute age?

What is the difference between relative and absolute age? Relative age: comparing rock layers and events to one another to determine age. Phrases such as older/younger than, first-second-third are used. 3 laws used to do this: original horizontality, superposition, cross-cutting relationships Absolute age: finding the actual age, or narrow range of time, of a rock layer by dating igneous material found in rock layers or “bracketing” using igneous volcanic ash. Using the half-life of radioactive material found in igneous rock allows us to do this.

What is the Law of Original Horizontality?

What is the Law of Original Horizontality? Sedimentary rock is formed in horizontal layers

What is the Law of Superposition?

What is the Law superposition? In undisturbed sedimentary rock layers, the oldest layer is at the bottom, youngest layer is at the top of the rock layers

What is the Law of Cross Cutting Relationships?

What is the Law of Cross Cutting Relationships? Anything that cuts through a rock layer is YOUNGER than the rock layer it is in

Putting it together to find relative age: Earth’s history is revealed in rock layers. Sedimentary rock layers contain fossils, intrusions, cracks, unconformities and folds that tell us what was happening on earth’s surface at different points in time Comparing fossils (index) and rock layers tell us what happened first, second…..relative age Oldest layer is on the bottom, younger on top Distortions in rock layers occurred after the layer(s) they changed http://study.com/academy/lesson/what-is-relative-dating-law-of-superposition-principles-of-original-horizontality-cross-cutting-relationships.html

Oldest to youngest…… A B C D E F

F E C B D (INTRUSION) A (UNCONFORMITY) A B C D E F

OLDEST TO YOUNGEST… Y

OLDEST TO YOUNGEST… Y Z A FAULT Q D Y

OLDEST TO YOUNGEST  X A B C D E F (10 MILLION YEARS OLD)

OLDEST TO YOUNGEST(BOTH ARE CORRECT) X F A B C D E F X A B C D E  X A B C D E F (10 MILLION YEARS OLD)

B C D E F (10 MILLION YEARS OLD) Using the absolute age of the intrusion…… E, D, C, B and A are older than 10 million years old  X A B C D E F (10 MILLION YEARS OLD)

1 2 3 4 Using the diagram to the right Describe the age of the fossil Using layer 1 Using layer 4 Using layer 2 1 2 3 4

1 2 3 4 Using the diagram to the right Describe the age of the fossil The fossil is older than layer 1 The fossil is younger than layer 4 The fossil is the same age as layer 2 Using the diagram to the right Describe the age of the fossil Using layer 1 Using layer 4 Using layer 2 1 2 3 4

1 2 3 4 Using the diagram to the right Describe the age of the fossil B 1 2 3 4 A B C

Fossil B is the same age as fossil C Fossil B is older than fossil A 1 2 3 4 A B C

What makes a good index fossil?

What makes a good index fossil? Lived a brief period of time (not found in a lot of vertical rock layers) Lived in a large global area (found in the same horizontal layers across the globe) (Easy to see in a rock layer)

Which of these is probably an index fossil GA G CG C CBA A B CA CB AC

Which of these is probably an index fossil GA G CG C CBA A B CA CB AC G…..IT IS FOUND IN A LARGE GEOGRAPHIC AREA (SAME HORIZONTAL LAYERS) BUT DID NOT LIVE A LONG TIME (MULTIPLE LAYERS)

You have found an area of North Carolina with an abundance of fossils You have found an area of North Carolina with an abundance of fossils. What kind of rock are you looking at? How do you know?

You have found an area of North Carolina with an abundance of fossils You have found an area of North Carolina with an abundance of fossils. What kind of rock are you looking at? Sedimentary rock How do you know? Heat and pressure involved in igneous and metamorphic rock process destroys remains

What kind of evidence do we get from ice cores and tree rings?

What kind of evidence do we get from ice cores and tree rings? Global climate evidence Bubbles  CO2 levels in ancient air indicate temp levels. Also used in current computer model predictions of global warming. Volcanic ash  evidence of volcanic eruptions Pollen  spores evidence of environmental conditions Tree rings Ring width  very specific, local information about precipitation levels Burn scars  forest fire evidence Irregular banding  crowding, wind conditions

Tree Ring

Ice Core Increasing levels of CO2 are linked to increasing global temperatures. Using isotopes of Carbon we know that in the last 450 years, the increasing CO2 levels are coming from human burning of fossil fuels, not volcanoes!

Absolute Age Allows the calculation of ancient rock and fossil age..puts a number on age Half life of radioactive material found in volcanic intrusions & volcanic ash. (the time it takes half a radioactive parent sample to break down into a stable daughter material)

How much time has passed if 75% parent material remaining 25% parent material remaining

How much time has passed if 75% parent material remaining ½ yr (6 mos) 25% parent material remaining 2 yrs

Different radioactive isotopes are used to date different materials. rocks dead organisms, <57,000 yrs old

Carbon-14 dating uses a radioactive isotope of carbon Carbon-14 dating uses a radioactive isotope of carbon. It has a half life of 5,700 years. It has a useful time of ~60,000 years. It is ONLY USED on remains of LIVING THINGS Other isotopes (uranium, chlorine..) have very long half lives (millions of years.) They have a useful range of millions to billions of years. They are used to date rock layers, fossils and remains of NONLIVING THINGS

Geologic Time Scale What is it How is it divided Describe the major time periods

Geologic Time Scale What is it? Fossil evidence in rock layers How is it divided major events (extinctions & radiations) Describe the major time periods Precambrian: single celled life, most of earth’s history is in precambrian time, ends with mass radiation of life Paleozoic era: most life in the sea, age of amphibians, ends with mass extinction Mesozoic era: age of reptiles, dinosaurs, no ice—humid, ends with mass extinction…meteor strike Cenozoic era: current, age of mammals

EONS – largest division of time 1. Hadean 2. Archean 3. Proterozoic 4. Phanerozoic #1-3 make up Precambrian Time Eons -> Eras -> Periods -> Epochs Change in name is due major geologic or climatic events!!

PRECAMBRIAN TIME 90% of Earth’s history Lasted nearly 4 billion years of Earth’s 4.6 billion years Volcanic ash & dust ->clouds formed ->rain Single-celled micro-organisms in ocean at end No animals No plants

3 Eras make up the Phanerozoic Eon: Paleozoic Era – “Age of Amphibians” Mesozoic Era – “Age of Dinosaurs” Cenozoic Era – “Age of Mammals”

Paleozoic Era = “Ancient” 544 mya – 248 mya All life in ocean until end Fish developed Reptiles, Insects, Ferns developed – moving life onto land at end Ends with a Mass Extinction kills 90% of all ocean species

Mesozoic Era = “Middle” 248 mya – 65 mya Dinosaurs rule! Small mammals, birds, flowering plants Ends with Mass Extinction due to meteor strike off Mexico ->dust cloud blocked sunlight, killed plant life and affected food chain

Cenozoic Era =“Recent” 65 mya – Present Large warm-blooded mammals, modern birds, flowering plants Animals developed migration techniques Tertiary Period Quaternary Period = last 2 million yrs Ice ages 1st modern human fossils = 100,000 yrs old Humans are 7 seconds of 12 hour clock!!

Why study fossils?

Why study fossils? They show us how life has changed over time. The Geologic Time Scale show us how changes in earth’s surface & climate have affected changes in organisms.

Over time, Life began as single celled Organisms and became More diverse and complex