Plate Tectonics

• Many asteroids smash into each other over time become one big ball (protoplanet) 2.All the collisions have caused much heat and radioactive decay • Because asteroid has become so big, the heat can no longer escape out of the mass as fast, which causes melting • This now lava ball allows the movement of elements (called differentiation): heavier ones sink to the core while lighter ones float up

Mg, Fe

Li, O, C

• Lowers melting point of mantle • Lowers viscosity So greater flow of lava and better convection (allows heat to distribute itself, circulating up from earths core)

Closer to the sun May once have had water but now it has all evaporated Internal heat cannot escape (no help from water) so venus remains very hot and crusts remelts ever couple thousand years

Smaller mass, so cooling occurs faster Probably had liquid water but because cooling occured to quickly, it froze Mantle lacks convection and flow (too solid/viscous), internal heat engine no longer functional –> heat production drives convection in earths mantle

• primordial heat: Heat from when Earth was forming (asteroids smashing etc)–> Earth is still releasing this heat • Radiogenic heat: TRadioactive decay of elements such as Uranium, Potassium and Thorium decaying into diferent elements release heat as by product

• Crust • MOHO 3.Lithosphere (Mantle) • Asthenosphere (Mantle) • Transition zone (Mantle) 6.Outer and inner core

Crust and mantle boundary Depth varies depending on thickness of crust Densite change above and below this boundary (S and P waves travel faster below this boundary so easy to detect)

RIGID upper mantle

DUCTILE/plastic Lithosphere- asthenosphere boundary (LAB) found at isotherm aka constant temp of 1280°

Found between upeper and lower mantle Seismic wave behaviour change because of olivine structure change at this pressure (increase pressure, atmons more tighlty packed)

Outer = LIQUID Inner = SOLID (because high pressure) Spin of Earth causes turbulent convection in outer core producing magnetic field

Silicon Oxygen Aluminum Iron Calcium Potassium

Formed by divergent plate boundaries Esentially solidifed mantle, mnantle exposed to surface and cools (to form mid atlantic ocean ridges MORB) Thinner (7-10km) Consists of heavier elements such as Fe and Mg

Formed by converging or subducting plates Thicker Less dense

-Large stable areas in the middle of areas of continental crust -low relief -Extremely old rocks (composed of precambrian crystalline rocks, some as old as 2-3 billion years old–> anything older has already been “reclycled”) -continetal “nuclei”, surrounded by belts of folded, younger rocks

“Simple”, layered structure 1.Sediment 2.Pillow basalts in rift zones, molten lava erupts from cracks and cools very fast as it comes into contact with the water 3.Basalt dykes underground plumbing system that brings magma from mantle onto ocean floor, essentially fractures caused by the extensional environment. 4.Gabbro Same composition as basalt, just bigger crystals cause slower cooling) 5.Peridotite

Because continental crust is less dense and hot, it doesn’t get subducted, instead it folds and crumples getting thicker and thicker It consists of: -intensley deformed metamosphic rock, typically more granitic/felsic than its mafic counterpart (oceanic crust) -rocks near the center are geenrally the oldest: protliths consisting of basalt and andesite and volcanic derived deiments such as the black sand in the canary islands (erosions of volcanoes)

Belts/layers of younger rock have undergone intense deformation (episodes of mountain building) They become welded against pre-existing shields. This accumulates and crumples further. Since it is also more felsic in composition, it is less dense and is even less likely to be subducted, so it will keep getting bigger and bigger

Mountains don’t keep growing because erosion occurs. And also: ISOSTASY

The lithosphere (rigid), weighs the asthenosphere (ductile) down –> where lithosphere is thick, asthenisohere is thin (MOHO is lowered) When erosion occurs, the load of the lithosphere lightens. Then asthenosphere is ductile, so asthenosphere can bounce/move back. The crust is ISOSTATICALLY UPLIFTED

Contour lines are parallel to geological boundaries of rock: HORIZONTAL BEDS Dipping boundaries that cut across contour lines, smoothing or accentuating contour lines: DIPPING BEDS Boundaries cuz straight across topography: VERTICAL BEDS