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Canada (158,173)
EESA06H3 (234)
Nick Eyles (205)
Chapter 4

chapter 4

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University of Toronto Scarborough
Environmental Science
Nick Eyles

Chapter 4 The Earths Interior the earths crust is a thin skin of rock earth is divided into three major layers o the crust o the mantle o the core seismic reflection and refraction suggest that the continents are largely igneous and metamorphic rock, such as granite and gneiss, overlain by a veneer of sedimentary rocks geophysics the application of physical laws and principles to a study of the earth seismic reflection the return of some of the energy of seismic waves to the earths surface after the waves bounce off a rock boundary o these reflected waves are recorded on a seismogram, which shows the amount of time the waves took to travel down to the boundary, reflect off it, and return to the surface seismic refraction the bending of seismic waves as they pass from one material to another o as a seismic wave strikes a rock boundary, much of the energy of the wave passes across the boundary o as the wave crosses from one rock layer to another, it changes direction occurs only if the velocity of seismic waves is different in each layer What is Inside the Earth? it was the study of seismic refraction and seismic reflection that enabled scientists to plot the three main zones of the earth the crust o the outer layer of rock, which forms a thin skin on earths surface o it is thinner beneath the oceans than beneath the continents o seismic waves travel faster in oceanic crust than in continental crust o the two types of crust are made up of different kinds of rock o seismic P waves travel through oceanic crust at about 7 km per second, which is also the speed at which they travel through basalt and gabbro o the upper part of the oceanic crust is basalt, and the lower part is gabbro o seismic P waves travel more slowly through continental crust o continental crust is often called granitic o the continental crust is highly variable and complex, consisting of a crystalline basement composed of granite, other plutonic rocks, gneiss, and schists, all capped by a layer of sedimentary rocks o felsic (rocks high in feldspar and silicon) is used for continental crust o mafic (rocks high in magnesium and iron) is used for oceanic crust o seismic waves show that the crust is thickest under geologically young mountain ranges o the continental crust is also dense than the oceanic crust o the boundary that separates the crust from the mantle is called the Mohorovicic discontinuity o the mantle lies closer to the earths surface beneath the ocean than it does beneath continents the mantle o made of solid rock o because P waves travel at about 8 km per second in the upper mantle, it appears that the mantle is a different type of rock from either oceanic crust or continental crust www.notesolution.com
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