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UT - GEOS 401 - Study Guide

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UT - GEOS 401 - Study Guide

School: University of Texas at Austin
Department: Geoscience
Course: Understanding the Earth
Professor: Jaime Barnes
Term: Summer 2015
Tags:
Name: The GEO 401 - Understanding the Earth - Study Guide - Geology Exam 1 Big Bang
Description: Geology Exam 1  Big Bang o Big Bang was 13
Uploaded: 04/05/2017
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background image Geology Exam 1  Big Bang o Big Bang was 13.7 billion years ago
o Condensation of our solar system by ca.4.56 GA
Age of the Earth o Oldest rocks are about 4 GA
o Earth is 4.6 GA from meteorites and the moon
Nebular Hypothesis 1. Diffuse, slowing rotating cloud begins to contract due to 
gravity
2. As a result of contraction and rotation, a flat rapidly 
rotating disk forms with the matter concentrated at the center
that will become the proto sun
3. Begins to spin faster and flattens and the proto-sun 
becomes dense and hot- nuclear fusion
4. The enveloping disk of gas and dust forms grains hat 
collide and clump together into small chunks or planetesimals
5. Gas condenses and collides with dust to form planetesimals
6. Planetesimals collide and accrete to form planets
The Solar System 1. Inner planets are small and rocky (Venus, Earth, 
Mercury, Mars)
2. The 4 giant outer planets and their moons and gaseous,
w/ rocky cores
3. Pluto is a snowball of methane, water, and rock The Moon o Impact of a mars sized body with proto-earth at about 4.56,  Collision tilted the Earth’s spin axis o Ejected material formed the moon Differentiation of the Earth o During this process, iron sank to the center and lighter  material floated upward to give us Earth as a zoned planet Layers of the Earth o Earth’s density is 5.5 g/cm^3 Denser material deeper in the Earth o Meteorites- pieces of broken planets
o Sometime in the Earth’s past, most of the Fe and Ni sunk 
inward to its center due to gravity  Crust o Most continental crust is thick
o Less dense continental crust floats on denser mantle 
1
background image o Continental crust is less dense that oceanic crust
o Low-density silicate minerals ( O, Si, Al, K) 
Continental Crust 40 km thick Density- 2.8 g/cm^3 Oceanic Crust 7 km thick Density- 3 g/cm ^3 o Moho separates crust from the mantle Mantle o 2/3 of Earth’s mass (most of planet)
o High density silicate materials (O, Si, Mg, Fe, Ca)
o Density 3.4 g/cm
o Upper- 100 km is strong, rigid
o Below 100 km is weak and deformable, ductile (Plastic)
Core o Solid and Liquid core
o Outer Core
Mostly FE, but also Ni, S,O Liquid because of temperature Density is 11/gm^3  o Inner Core Mostly Fe, but also Ni Solid because of pressure Density is 13/gm^3 Seismic Waves o Compressional (P-waves; pass through solid, liquid,  gas)expand and compress material they move through o Shear- (S-waves; pass through solid only) move the material  side to side  o Variations in seismic wave velocity at different depths reflect  changes in composition Seismology is one of the primary tools geologists use to
study the Earth’s interior. 
99% of the Earth is made up of Fe, Si, O, Mg, Al, Ca, Ni, S Plate Tectonics o Lithosphere- crust + top of mantle (100km) cold, strong rigid)
o Asthenosphere- weaker part of the upper mantle; hot, weak 
ductile EX: hot wax or silly putty (solid that flows) Temperature Gradient (Geotherm)  o Temperature is largely responsible for plate tectonics  2
background image Study Diagram warm material rises and cool sinks Convection-when hotter material rises and cooler material sinks o EX: think of a pot of oatmeal 1. Divergent-move away
2. Convergent- pushed against one another (and one 
goes down)  3. Transform- slide past eachother  o As plates age or move away from the ridge they cool  and become denser o Eventually they become denser than the underlying  mantle and they sink o Plate movements are driven by the pull of sinking plates at subduction zones Theory of Plate Tectonics o Lithosphere is broken into several semi-rigid plates that move over the asthenosphere in response to mantle convection o Interaction b/w plates causes earthquakes, volcanoes and  mountain belts Continental Drift o Proposed by wegnener in 1915 ( based on Pangaea) Evidence for Pangaea includes distribution of rock 
assemblages ages, fossils, glaciation ( mostly in Africa 
and South America)
Seafloor Spreading o Seafloor bathymetry- rifts Earthquakes showed the seafloor to be tectonically 
active along those rifts
Magnetism and the age of crust Seafloor Magnetic Anomalies o Basalt is extruded at ocean ridges(Basalt is melted mantle)
o Basalt records the magnetic field at the time of cooling
o Crust moves away from the ridges and becomes older
Magnetic Time scale  o Geologic time-series show that Earth’s magnetic field  periodically reverses. Sometimes a compass points north, 
sometimes south.
Can be divided into periods when the magnetic field is 
primarily normal and when they are reversed.
Magnetic anomalies are symmetric across a ridge. Youngest rocks 
are near a ridge. Oldest rocks are near a continent. 
3
background image Rates of Plate Motion o Velocity= distance/time
o Fast spreading: 10cm/year
o Slow spreading: 3cm/year
Plate Boundaries o Divergent (mid-ocean ridges and spreading centers) Occur at zones of upwelling mantle Produces new oceanic crust Basaltic volcanism Small, shallow earthquakes Normal faults High heat flow o Convergent Denser or oceanic plate is subducted Types of Convergent Boundaries Continent-Continent Ocean-Continent Ocean-Ocean Explosive andesitic volcanism Intrusion of granite at depth Large Earthquakes, shallow to deep Metamorphism, folds, thrust faults o Transform Boundaries Types of Transform Boundaries Mid-Ocean Ridge transform Continental transform fault No igneous activity Not metamorphism Large, shallow earthquakes Strike-slip faults Hot spots diagram Lead to a chain of volcanic islands Mantle plumes diagram Caused by instability at the core mantle Come from core mantle boundary Earth Materials o Minerals and rocks record important events, changes and  conditions that have occurred during the history of the Earth o Principle of Uniformitarianism  Present is the key to the past 4

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Join more than 18,000+ college students at University of Texas at Austin who use StudySoup to get ahead
School: University of Texas at Austin
Department: Geoscience
Course: Understanding the Earth
Professor: Jaime Barnes
Term: Summer 2015
Tags:
Name: The GEO 401 - Understanding the Earth - Study Guide - Geology Exam 1 Big Bang
Description: Geology Exam 1  Big Bang o Big Bang was 13
Uploaded: 04/05/2017
13 Pages 15 Views 12 Unlocks
  • Better Grades Guarantee
  • 24/7 Homework help
  • Notes, Study Guides, Flashcards + More!
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