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Geology Lecture 2

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What are the four main chapters of earth
Cenozoic (todays earth) Mesozoic (dinosaurs), Paleozoic (shells and other hard body parts), Precambrian
define: phanerozoic
visible life
How are fossils preserved?
-hard parts remain -bones in fragments remain -replaced by silica, pyrite ect. -leaves a cavity in the rock of the animals shape -leave impressions -insects trapped in tree sap -worms create worm burrows
What happened between the boundary between: -Cenozoic and mesozoic -Mesozoic and Paleozoic -Paleozoic and Precambrian
Cenozoic and Mesozoic= mass extinction of dinosaurs -mesozoic and Paleozoic= The Great Dying Paleozoic and Precambrian= widespread appearance of hard shelled organisms
Whats the oldest dated rock on earth?
4.28 billion years old
Whats the oldest dated mineral on earth?
4.36 billion years old
How old did Archbishop Ussher say the earth was?
using the bible he said the earth was born Oct. 23rd 4004 BC (6,000 years old)
Who came up with the Principle of Uniformitarianism?
James Hutton. Father of Geology. "The present is key to the past."
how old is the earth do we estimate now, how do we know?
4.5 or 4.6 billion years old. We use Radiometric age dating of meteorites (Uranium to Lead)
who came up with the idea of continental drift? What was his evidence?
Alfred Wegener. Evidence: continents fit, similar rocks in Africa and SA, evidence of same climates, fossil record
when was the sea floor mapped?
ww2
What is oceanic crust made out of?
basalt and its dense and thing
What is continental crust made out of?
granite and its not dense and its thick
Where do we find earthquakes
concentrated in discrete belts
where do we find volcanoes?
along belts
Where do we find mountains?
along a plate or what used to be a plate
How do plates move?
Divergent, Convergent and Transform
What happens at a divergent boundary?
ocean/ocean: a narrow trough called a rift forms. Earthquakes, magma erupts onto the sea floor. Called seafloor spreading Continent/Continent: same thing, only water gets trapped. example: Red sea
why are mid ocean ridges less dense than the ocean around it
mid ocean ridges are higher thant he surrounding seafloor because they are hotter, less dense and a thinner lithosphere
What happens are a converge boundary?
ocean/ocean: the older one gets subducted. The older the crust the steeper the angle Ocean/continental: ocean is subducted. When the ocean lithosphere gets deep enough it melts and becomes either a pluton or a volcano continent/continent: mountains
What causes the ring of fire?
result from subduction on both sides of the pacific ocean
What is each layer inside of the earth made out of?
Crust: Continental (granite) Ocean (basalt) Mantle: olivine Outer Core: iron and nickel Inner Core= iron and nickel
What is part of the lithosphere?
crust and upper most mantle. Its very brittle
What is part of the asthenosphere?
the rest of the mantle. Like gum
Define: Superposition
the youngest layer formed first. You can't deposit a sedimentary rock underneeath another layer. The exception is Magma.
Define: Cross-cutting relationships
"You can't cut through something that doesn't exist already." Younger rocks and features can cause changes along contact with older rocks.
Define: Unconformities
a gap in time in the geologic record
what are the types of unconformities?
Angular unconformities (fold the layers, then eroded) Disconformities (flat, erodes away) Nonconformity (sedimentary layers deposited on top of igneous or metamorphic rocks)
Define: Isotope
atoms with the same number of protons but different number of neutrons
92 U 238.03 Give me the Protons, neutrons, atomic number, atomic weight
protons: 92 neutrons: 143 atomic number: 92 atomic weight: 238.03
What are the assumed conditions for radiomentric age dating?
known parent/daughter ration in initial sample Isolated system (no contamination or parent/daughter lost) decay is constant
Why is radon special?
its a gas
What can isotopic age tell us?
age of eruption age of solidication age of metamorphic events when a rock cooled age of source of sediment age of recent sediment
What special things did Charles Lyell come up with?
the Principles of Geology. Many things that have happened on the earth are cumulative, not catastrophic. Give enough time and the earth will change.
Which period are we in? And which epoch have humans been around for?
Period: Quaternary Epoch: Pleistocene (1.8 million years ago) Holocene (.01 million years ago)
Define: Moho
boundary between the crust and the mantle
Where is there oceanic subducting oceanic crust
Japan, Indonesia, Philippines
Where is there continental crust crashing into continental crust?
Himalayas
Define: Benioff zone
shows you how steep the crust is being subducted by earthquakes
Define: Paleomagnetism
the history of magnetic north
Why is Harry Hess important?
first person to say the sea floor in the Atlantic ocean is spreading.
Define: The Principle of Faunal Succession
The Principle of Faunal Succession is the concept that fossils succeed each other in the rock record in a reliable (and predictable) order.

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