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plate tec - Coggle Diagram
plate tec
theory
convection current: heat from earths core causes mantle material to become less dense. the mantle material then rises to the surface of the earth. convection currents spreads beneath the plates, dragging them apart, known as the divergent plate movement. the mantle material then loses heat and sinks to the core.convergent plate movement is when the convection currents collide with one another. then the mantle material gains heat again and the whole thing repeats
slab pull force: when two plates collide, the denser plates subjects under the less dense plate.the denser plate subducts and is pulled down by gravity. it further sinks deeper when it is pulled by its own weight, contributing to further convergence
evidence of plate tec
seafloor spreading: when two oceanic plates diverge, seafloor spreading occurs. the magma rises to the surface of the earth through the mid ocean ridge and forms the new coenaic crust. it is found that the rocks nearer to the mic ocean ridge is younger than the rocks laterally further away from both sides of the ridge
magnetic striping: refers to the zebra like pattern of the alternating bands of normal polarity rocks and reverse polarity rocks.
movement
divergent
O-O divergence: 2 oceanic plates diverge. the decrease in overlying pressure on underlying mantle causes the underlying mantle to melt, forming magma. magma rises to the surface of the earth to fill up the gaps between the crust. the lava cools, solidifies to form basaltic rocks. the mid ocean ridge can eventually form an extensive underwater mountain chain. in the middle of the mid ocean ridge is a Rift Valley with steep sides. magma rises to the surface to erupt as lava, lava cools solifidifies and accumulates to form a volcano. after many eruptions, the volcano break the surface of the water to form a volcanic island. earthquakes also occur here due to the tension and stress released
EXAMPLE: mid Atlantic ridge is the worlds longest ridge of 56000km long, North American and eurasian plates diverging
C-C divergence: 2 continental plates diverge. case cracks in the rocks known as faults. the faults then widens to form a deep Rift Valley. the lan between the two sides of the Rift Valley is known as block mountains. as the plates move apart, the decrease in overlying pressure on underlying mantle causes the mantle to melt, forming magma. the magma then rises to the surface of the earth to erupt as lava the lava cools solidifies and accumulates to form a volcano. earthquakes are common here due to the tension and stress released from the two plates diverging.
EXAMPLE: somalia plate ad nubia plate diverge, forming the great Rift Valley, and also mount Kenya and Mount Kilimanjaro volcanoes
convergent
O-O convergence:when 2 oceanic plate collide, the denser plate sinks beneath the less dense plate. this forms a deep depression known as an oceanic trench. as the denser plate subducts, the high pressure forces water out of its oceanic crust. water lowers the melting point of the mantle and from magma. magma rises to the surface of the earth to erupt as lava then the lava cools solidifies and accumulates to form a volcano, which subsequently forms a chain of volcanoes known as volcanic island. earthquakes also occur due to the friction between plate boundaries.
EXAMPLE: oceanic philippine plate converges with the oceanic pacific plate: forming the Mariana Trench and Guam islands, an island near the Mariana Trench often suffer from earthquakes.
C-O convergence: when two plates collide, the denser oceanic plate subducts beneath the less dense continental plate this forms a deep depression known as oceanic trench on the oceanic plate. a the oceanic plate subducts, the high pressure forces water out of its oceanic crust. water lowers the melting point of mantle, forming magma. magma rises to the surface of the earth and erupts as lava. lava cools solidifies and accumulates to form a volcano not he continental plate. the rocks on continental plate also buckle and fold, forming fold mountains. earthquakes also occur here due to the friction between plate boundaries.
EXAMPLE: oceanic nazca plate collides with South American plate, forming the; Peru Chile trench, andes fold mountain range and nelvado del Ruiz volcano earthquakes are common here like the 2010 Chile earthquake
C-C convergence: when two continental plates converge, there is no subduction as the continental plates are too buoyant to subduct. there is no magma rising to the surface hence there is no volcano formed. rocks buckle and fold, forming fold mountains. earthquakes occur here due to the friction between two plate boundaries
EXAMPLE: the Indo Australian plate collides with the eurasian plate, forming the Himalayas fold mountain range. earthquakes are common here like the 2015 Nepal earthquake
transform: pacific plate and north American plate slide past one another. stress from seismic waves causes earthquakes to occur. magma does not rise to the surface hence no volcano is formed, forms the san areas fault (stress caused by plate produces a fault)
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