CAS ES 107 Chapter Notes - Chapter 7: Lithification, Silicate Minerals, Seismic Tomography
7 Jun 2018
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Chapter 7: Circulation of Solid Earth
-German meteorologist Alfred Wegener created the theory of plate tectonics, Pangea (continental
drift)
-plate tectonics→ earth’s surface is divided into rigid plates of continent and ocean floor that
move relative to each other through time
-tectonics→ study of earth’s crust and the processes that deform it
-Pangea→ meaning Earth, the proposed landmass like a supercontinent before that broke apart
just after the Mesozoic era, 200 million years ago, before they moved to their present areas
Earthquakes
-everything we know about earth’s interior is because of seismology: the study of earthquakes
and related phenomena
-earthquake→ the sudden release of stored energy as a result of rapid movement between two
blocks of rock
-focus→ the site of the energy release
-epicenter→ position on earth’s surface directly above the focus
-earths uppermost shell, or surface, is rigid so when it deforms it does so elastically meaning the
material recovers it shape after the force is removed, unless it is deformed to the point of fracture
Seismic Waves
-these waves ripple through earth’s interior, away from the earthquake’s focus, as a result of that
deformation
-two types of seismic waves: body (travel through interior) and surface waves (travel across
surface)
-energy is transmitted away from the center
-P waves→ primary waves, result from compression of material in earth’s interior
a. travels as a series of compressions and expansions in the direction of wave movement
(pushing neighbors shoulders down the ling, slinky)
b. can go through both solids and liquids
-S waves→ secondary or shear waves, are transmitted as displacement perpendicular to the
direction of the wave (like a spring swung side to side, or wave of shoulders down line)
a. only solids can transmit S waves, NO LIQUIDS
-eventually all body waves intersect earth’s surface which can be detected and recorded with a
seismograph: sensitive instrument that detects slight vertical and horizontal displacements of
earth’s surface
-the rate at which body waves travel depends on the properties of the material in earth
-by comparing several seismographic records from various places around the world for one
event, we can construct a fairly detailed 3D view of the paths of the seismic waves (seismic
tomography)
-the crust is not homogenous because it varies in thickness and composition
-the main difference are between the continental and oceanic crust
-continental crust→ underlies continents, less dense than oceanic crust, and older
-oceanic crust→ underlies ocean basins and is more dense
find more resources at oneclass.com
find more resources at oneclass.com
Document Summary
German meteorologist alfred wegener created the theory of plate tectonics, pangea (continental drift) Plate tectonics earth"s surface is divided into rigid plates of continent and ocean floor that move relative to each other through time. Tectonics study of earth"s crust and the processes that deform it. Pangea meaning earth, the proposed landmass like a supercontinent before that broke apart just after the mesozoic era, 200 million years ago, before they moved to their present areas. Everything we know about earth"s interior is because of seismology: the study of earthquakes and related phenomena. Earthquake the sudden release of stored energy as a result of rapid movement between two blocks of rock. Epicenter position on earth"s surface directly above the focus. Earths uppermost shell, or surface, is rigid so when it deforms it does so elastically meaning the material recovers it shape after the force is removed, unless it is deformed to the point of fracture.
