* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download astron_ch_7c (1)
Survey
Document related concepts
Geomagnetic reversal wikipedia , lookup
Spherical Earth wikipedia , lookup
Post-glacial rebound wikipedia , lookup
History of geomagnetism wikipedia , lookup
Physical oceanography wikipedia , lookup
Schiehallion experiment wikipedia , lookup
History of Earth wikipedia , lookup
Age of the Earth wikipedia , lookup
History of geology wikipedia , lookup
Geological history of Earth wikipedia , lookup
Mantle plume wikipedia , lookup
Future of Earth wikipedia , lookup
Transcript
Sponge: List the layers of the Earth’s atmosphere. Earth’s Interior Crust - ~15 km thick, 8 km under oceans, 20-50 km under continents, 3 density of 3 g/cm Mantle - dense, but rocky material, 80% of Earth’s volume, 3 density 5 g/cm Outer core - liquid 3 density ~ 8 g/cm Inner core - solid density is compressed 3 to 12 g/cm The inner and outer core are both the same temperature and are made of the same material: nickel and iron. This separation of the parts of a planet (or moon) by density is called differentiation. The Earth was molten in the past which allowed differentiation to occur. The Earth was molten due to the bombardment by other materials and radioactive decay. The upper mantle is made of basalt 3 (3.5 g/cm ); the continents are made of 3 granite (3 g/cm ) which can float on the mantle. The Earth’s central core temperature is nearly equal to the Sun’s surface temperature. 5000K 8500°F Surface Changes Plate Tectonics - the Earth is covered by surface plates which move individually. This movement was detected by comparison to quasars. The plates are not necessarily the continents themselves. Some are continents plus ocean floors (Indian plate). Some are all ocean floor (Nasca plate). All of the plates together form the Lithosphere. The lithosphere is the portion of the Earth that undergoes tectonic activity. It is made up of the crust and a small part of the upper mantle. The semisolid part of the mantle over which the plates slide is called the Aesthenosphere. One of the largest divisions between plates is the MidAtlantic Ridge which separates the North American Plate from the Eurasian Plate and the South American Plate from the African Plate. Collisions between plates cause (1) mountain ranges (like the Himalayas) or (2) subduction zones where one plate slides under the other, ultimately to be destroyed. This is responsible for most deep ocean trenches. Not all plates collide, some “shear” past each other (San Andreas Fault). Sudden, jerky slippages of these faults cause earthquakes. Some plates move apart (as in the Atlantic Ocean). In these cases, the mantle material wells up forming ridges (Mid-Atlantic Ridge). What moves the plates? Probably convection currents in the mantle. Continental drift was proposed in 1912 by Alfred Wegener. What evidence is there for continental drift? 1. Geographical evidence the continents fit together. 2. Fossil evidence Fossils of an extinct reptile are found only on the Brazilian coast and the west coast of Africa. 3. Ocean floor age The ocean floor close to the Mid-Atlantic Ridge is young, farther away on either side gradually gets older. 4. Paleomagnetism the Mid-Atlantic Ridge shows matching reversals of the Earth’s magnetic field on either side of the ridge.