Midterm 1 Study Guide

Midterm 1 Study Guide - Midterm 1 Study Guide Time in the...

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Unformatted text preview: Midterm 1 Study Guide Time in the Earth Sciences Absolute time get absolute date from radiometric dating Relative time based on fossil records Radioactive isotope occurs at a constant rate independent of temperature or pressure o Half life divide by 2 Age of earth 4.6 billion years old (determined by dating meteorites) Age of rocks oldest rocks 3.96 billion years old, use isotope that has big enough half life (uranium) Oldest continental rocks occur at the center of continents (Greenland) Oldest oceanic rocks 200 million years old (at the colliding edge of the plate boundary) Oldest fossils 600 million years old Power of ten notation 10 9 = 1,000,000,000 Age of sun/other planets all 4.6 billion years old Age of universe 13.6-15 billion (known because the universe is expanding) What is an earthquake? What is an earth quake sudden slip in fault plane o Fault plane place of weakness around a fault trace o Fault trace surface line, intersection between the fault plane and the earths surface, can be a curved line o Fault scarp a cliff or steep slope formed by displacement of the ground surface o Hypocenter (focus) point where earthquake starts (lat, long, depth), locate using arrival times of earthquake seismic waves at an array of stations o Epicenter point directly about the hypocenter on the earths surface (lat, long) Where do earthquakes occur and why? Where do earthquakes occur at plate boundaries Oceanic crust is thicker than continental crust o 3 types of plate boundaries Divergent two plates moving apart, mid-ocean ridges Convergent one plate moving up, one plate moving down, against each other, trenches/ island arc structures, subduction zone Transform sliding against each other, SAF/ facture zones linking sections of mid-ocean ridges Plate tectonics anything that raises topography (earthquakes, volcanoes, mountain building) o Lithosphere- the outer, rigid shell of the earth above the aesthenosphere, contains the crust, continents, plates, and uppermost mantle o Aesthenosphere layer below the lithosphere, it is the weaker, hotter, deeper part of the upper mantle o Mantle Convection slow motion of earths mantle in response to its variations in density, causes earthquakes and tectonics o Hot spots places on earths surface where hot mantle is stirring below, where active volcanism has occurred for a while where magma comes up, Hawaii o Continental Collisions subduction zone is destroyed, mountains are produced, two continents are sutured together, Himalayas, (convergent) o Deep-focus earthquakes occur in subduction zones (two tectonic plates meet and move towards one another, with one sliding underneath the other and moving down into the mantle) as deep as 700 km Earthquake epicenters are not randomly located on Earths surface o They occur in belts...
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This note was uploaded on 10/18/2009 for the course GEOL 240Lxg at USC.

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Midterm 1 Study Guide - Midterm 1 Study Guide Time in the...

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