Survey
* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download File
Document related concepts
Geochemistry wikipedia , lookup
Post-glacial rebound wikipedia , lookup
Deep sea community wikipedia , lookup
History of geomagnetism wikipedia , lookup
Spherical Earth wikipedia , lookup
Schiehallion experiment wikipedia , lookup
Plate tectonics wikipedia , lookup
History of Earth wikipedia , lookup
History of geology wikipedia , lookup
Large igneous province wikipedia , lookup
Age of the Earth wikipedia , lookup
History of geodesy wikipedia , lookup
Future of Earth wikipedia , lookup
Transcript
EXPLORING EARTH’S INTERIOR Chapter 14 Seismic rays are refracted away from the normal as they penetrate the earth, which causes them to bend, because each lower layer in the earth’s mantle becomes progressively more dense due to the weight of overlying rock. Seismic ray i High density and high strength Low density and Lower strength r Angle of incidence i < angle of refraction r S-wave paths through Earth’s interior. Focus 0° S wave 105° shadow zone between 5 Mantle and 105 Outer core degrees Reveals the earth’s liquid outer core S-wave shadow zone Inner core 105° The pattern of P-wave paths through Earth’s interior. Focus 0° P wave shadow 105° zone between 105 and 142 142° degrees Reveals the earth’s solid inner core P-wave shadow zone 142° 105° In order for rocks to melt within the earth, the melting curve for rock must be to the left of the geotherm (the earth’s temperature with depth). Note that this occurs only in the outer core and asthenosphere. It is even more interesting to consider that the melting curve for rock in this figure is for a wet asthenosphere. If the asthenosphere were dry, the melting temperature would be above the geotherm, and upwelling mantle would not melt. Focus Liquid outer core Solid inner core Mantle Seismic tomography uses the travel times from many earthquakes to create threedimensional images of Earth’s interior. Seismographic stations North America Africa A tomographic section reveals a mantle plume beneath South Africa,… North America Africa A tomographic section reveals a mantle plume beneath South Africa,… North America …and the remnants of the Farallon Plate under North Africa 70 km 70 km Near Earth’s surface, hot rocks in the asthenosphere slow S waves. 200 km 200 km Moving deeper, we see the cold lithosphere of stable continental cratons and warmer asthenosphere beneath ocean basins. 500 km 500 km Deeper in the mantle, the features no longer match the continental positions. 2800 km (near mantle-core boundary) 2800 km (near mantle-core boundary) Colder regions around the Pacific may be the “graveyards” of sinking lithospheric slabs.
