GEOL 101: Earth's Interior I & II
GEOL 101: Earth's Interior I & II 101-017
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This 4 page Class Notes was uploaded by Natalee Stanton on Saturday March 26, 2016. The Class Notes belongs to 101-017 at University of South Carolina taught by in Winter 2016. Since its upload, it has received 14 views. For similar materials see Geology 101-017 in Geology at University of South Carolina.
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Date Created: 03/26/16
GEOL 101 Earth’s Interior I. About the earth’s interior The center of the earth is about 6400 KM below us o Deepest well is 10 km Heat inside the Earth drives the core’s geodynamic and the mantel convection Earth’s interior is explored by using information form seismic waves and their passage through the body of the earth II. Stricture of the Earth Seismic velocity depends on the type of material (composition, temperature, and pressure o We can use the seismic waves to tell us about the interior of the earth When waves move from one type of material to another, they change speed and direction III. Behavior of waves and boundaries Waves travel with spherical waves fronts Reflection – when energy, reflects, back form the boundary between materials with different physical properties Refraction – when energy “refracts” (is transmitted but changes directions) at a boundary between materials with different physical properties o Think of a laser going through a fish bowl filled with water Passive source seismology Study of the earth’s interior using earthquakes as sources for seismic waves Earth’s layering: Velocities Densities Earth’s Interior II Structure of the earth Study of the behavior of seismic waves tells us about the shape and composition of the interior of the Earth Crust Mantle Outer core Inner core IV. Isostasy This is what causes an iceberg to float on water. o Mechanism by which the less dense continents float on the denser mantle o Over long periods, the mantle has little strength and behaviors Moho – is the seismically defined boundary between crust and mantle o In order for continents to be higher they must be thicker V. Role of Heat Many physical process on Earth are a result of heat and the distribution of temperature Melting of rocks (solid to liquid) Metamorphism Convection of the mantle Convection of the outer core VI. Earth’s internal Heat Original heat Subsequent radioactive decay Radioactive decay happens in the Earth’s curst Condition (lithosphere) : transfer of heat through matter with no particle displacement o Energy moves through the substance Convection (Mantle) – transfer of heat through matter though particle displacement o Move it from one place to another to cool off VII. Earth’s magnetic field It is much like field that would be produced by a giant bar magnet placed at the earth’s center Declination – horizontal angle between magnetic north and geographic north Inclination – angle made with horizontal o Not stable Outer core is made primarily form iron that is a good electrical conductor Convention in the earth’s outer core generates and maintains the magnetic field Geodynamo Rapid convection motion of the outer core generated electric current Self –exciting dynamo the sun’s magnetic field interacts with the moving iron in the core to produce and electric current yielding magnetic field VIII. Magnetic reversal Polarity of the earth’s magnetic field has changed thousands of time in the Phanerozoic The most recent reversal was about 8,000 years ago These reversals appear to be abrupt Magnetic epoch – a period of time in which magnetism is dominantly of one polarity o Oceans crust is a magnetic tape recorder o Normal – north oriented polarity o Revered – south polarity Paleomagnetism – permanent record of the direction of the earth’s magnetic field at the time the rock was formed o Use of magnetic properties of rocks to determine their age o Use of the earth’s magnetic field to investigate past plate motions Sample Exam Questions P seismic waves travel faster than S seismic waves. a. True b. False The shape of the earth is a sphere. a. True b. False What is the approximate distance from the surface to the center of the Earth? a. 700 km b. 2900 km c. 6400 km d. 24000 km Which layer in the Earth does NOT transmit S waves? a. Crust b. Inner core c. Mantle d. Outer core What type of seismic wave is depicted by the ray path in the diagram? a. P wave b. S wave c. A surface wave d. All of the above
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