Tectonic Plates. Lithosphere – outer part of the Earth’s crust. Composed of solid rock....
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Transcript of Tectonic Plates. Lithosphere – outer part of the Earth’s crust. Composed of solid rock....
Tectonic Plates
Lithosphere – outer part of the Earth’s crust. Composed of solid rock.Asthenosphere - the zone below the lithosphere which is more ‘plastic’ so it is easier to bend and moveRadioactivity is the sourc of heat in the mantle
Layers of Earth
2 Kinds of CrustContinental – less dense, thickerOceanic – more dense, thinner
2 Kinds of MantleUpper – solid, floats on…Lower – plastic (somewhat fluid)–Why?•Earth’s crust and upper mantle “float” on the plastic portion of the mantle. (asthenosphere)
Convection Currents
Movement of hot liquid or gas –Heated – rises–Cools – dropsEarth’s Crust Cracks…–Convection currents in mantle cause
cracking in crust–Thermal Convection cause seafloor
to spread and continents to drift
Divergent
Boundary
Convergent Boundary
Divergent – Ocean to Ocean
New crust formed and pushed up - Mid Oceanic Ridges–Ex. Mid-Atlantic Ridge
Ocean Ridges
Divergent-Continent to Continent Continent spreads, ocean basin may
formPaleontologist noticed that fossils were on different continentsArthur Holmes – First proposed that thermal convection in the mantle causes continental driftEx. Red Sea
Convergent –Ocean to Ocean
Older slips below newerSubducted plate melts–Volcanic islands formedEx. Aleutian islands, Japan
Convergent –Ocean to Continent
Ocean plate goes below continent– SubductionSubducted plate partially meltsTrenches – the deepest parts of the ocean.Volcanic mountains– Ex. Western South America
Aleutian Islands
Islands of Japan
Convergent – Continent to
ContinentSame densities, no subductionCompression, folding, upliftingEx. Himalayas, Alps
Transform faulting:Plates move past each other
Another type of plate movement…
San Andreas FaultSan Andreas Fault
How do you think scientists identified the plate boundaries?What is the “Ring of
Fire?”
Crustal Plates
“Connect the dots” – volcanoes and earthquakes8 major plates
Pangea Theory1912 – Alfred WegenerIdea that continents were once part of one large land mass – theory of continental driftHow did he know?–Continents’ shapes fit together like a
puzzle–Rocks and fossils found on different
continents matched
Early 1960sScientific evidence proves continental drift, plate tectonics, and Pangea theory
Ocean Features Picture 2