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.