Sponge: List the layers of the Earth

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Sponge List the layers of the Earths
atmosphere.
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Earths Interior -Crust - 15 km thick,8 km
under oceans,20-50 km under continents,density
of 3 g/cm3
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Mantle - dense, but rocky material,80 of
Earths volume,density 5 g/cm3
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Outer core - liquid density 8 g/cm3Inner
core - soliddensity is compressed to 12 g/cm3
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The inner and outer core are both the same
temperature and are made of the same material
nickel and iron.
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This separation of the parts of a planet (or
moon) by density is called differentiation.
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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.
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The upper mantle is made of basalt (3.5 g/cm3)
the continents are made of granite (3 g/cm3)
which can float on the mantle.
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The Earths central core temperature is nearly
equal to the Suns surface temperature.5000K
8500F
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Surface ChangesPlate Tectonics - the Earth is
covered by surface plates which move
individually. This movement was detected by
comparison to quasars.
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The plates are not necessarily the continents
themselves.Some are continents plus ocean floors
(Indian plate). Some are all ocean floor (Nasca
plate).
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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.
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The semisolid part of the mantle over which the
plates slide is called the Aesthenosphere.
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One of the largest divisions between plates is
the Mid-Atlantic Ridge which separates the North
American Plate from the Eurasian Plate and the
South American Plate from the African Plate.
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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.
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Not all plates collide, some shear past each
other (San Andreas Fault). Sudden, jerky
slippages of these faults cause earthquakes.
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Some plates move apart (as in the Atlantic
Ocean).In these cases, the mantle material wells
up forming ridges (Mid-Atlantic Ridge).
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What moves the plates? Probably convection
currents in the mantle.
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Continental drift was proposed in 1912 by
Alfred Wegener.
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What evidence is there for continental drift?
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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.
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3. Ocean floor age - The ocean floor close to the
Mid-Atlantic Ridge is young, farther away on
either side gradually gets older.
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4. Paleomagnetism - the Mid-Atlantic Ridge shows
matching reversals of the Earths magnetic field
on either side of the ridge.
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