Plate Tectonics

Mind Map by Sharondeep, updated more than 1 year ago
Created by Sharondeep almost 6 years ago


Undergraduate Physical Geography (The structure of the Earth) Mind Map on Plate Tectonics, created by Sharondeep on 03/20/2014.

Resource summary

Plate Tectonics
1 The crust is broken up in pieces called plates
1.1 Plates are driven by convection currents
1.1.1 Heat rising and falling inside the mantle creates convection currents Convection currents are created by radioactive decay in the core
1.2 The point where two plates meet is called a plate boundary
1.2.1 Volcanos and earthquakes are most likely to occur on or near boundaries
1.2.2 Plate tectonics cause earthquake and volcanoes
1.3 They move in different directions
2 History
2.1 Continental drift
2.1.1 Concept attributed to Alfred Wegener F.B Taylor independently came to the same idea Francis Bacon in 1620 first saw that the continents fit like a jigsaw Supercontinent - Pangea In Quaternary split to Laurasia in the north and Gondwanaland in the south Theory rejected at first as could not describe drifting the continents
2.1.2 Evidence Biology Mesosaurus, a small Permian reptile, found only in SA and Brazil A plant only existed in coal-forming times found only in India and Antarctica Geology Rocks of a similar age and type found only in SA and Brazil Like Mesosaurus Mountain ranges and fold belts all become consistent if fitted back into Pangean landmass E.g. NW European mountains and the Appalachians of the USA Climatology Evidence of glaciation found in tropical Brazil and central India Coal forms under warm, humid conditions, found in Antarctica Limestone found in England could not have formed under current climate
2.2 Later evidence for sea spreading
2.2.1 Paleomagnetism 1950's As molten lava cool on surface the material, iron, within align themselves with the magnetic pole creating a record of the Earth's magnetic polarity Symmetrical either side of the Mid Atlantic Ridge
2.2.2 1962 Maurice Ewing discovered mountain range extending the entire length of the Atlantic sea floor Rocks volcanic in origin and young He had discovered the Mid Atlantic Ridge
2.2.3 Harry Hess discovered rocks became increasingly younger towards the Ridge and the sea floor was spreading He confirmed the newest rocks were still being formed in Iceland However if new crust is being created it had to be being destroyed elsewhere as the world was not expanding in size Evidence found around the Pacific Plate tectonics theory was universally accepted Theory of the plates constantly moving, driven by convection currents
3 Plate boundaries
3.1 Constuctive
3.1.1 plates move away, new crust formed transform faults perpendicular
3.1.2 mainly between oceanic so underwater rarely on land E.g. East Africa, Great African Rift Valley It is said the Red Sea is the beginning of a new ocean, associated volcanoes include Mount Kilimanjaro and Mount Kenya
3.1.3 rift valleys initially, marked by ocean ridges
3.1.4 submarine volcanoes may grow above sea level e.g. Ascension Island on the Mid-Atlantic RIdge 73% of lava (magma after it reaches the surface) is found at mid-ocean ridges.
3.2 Destructive
3.2.1 2 plates move towards each other and one is subducted (forced below into the mantle)
3.2.2 Pacific ocean surrounded by them, perimeter is known as Pacific Ring of Fire
3.2.3 different plates converging means different features
3.2.4 OC vs CO = Oc dips, deep-sea trench forms, sediments pushed up to form fold mountains, heat generated by friction helps to melt platemagma less dense then mantle so rises and forms vol, des margins magma acidic so may cool before surface and form a Batholith at base of mountains shallow Eqs occurs as plate initially stretched and dipped. Deeper eqs arise from increased friction. At subduction zome where more eqs take place is known as the Benoiff zone greater subduction angles gives shallower eqs If occurs off shore Island Arcs may form E.g. Japan and WI
3.2.5 Oc vs Oc = either subducted
3.2.6 CO vs CO = very rare, Oc cannot sink so crumple to form deep-rooted fold mountains mark site of the Earth's thickest crust E.g. the Indo-Australian Plate is moving NE to the Eurasian Plate creating the Himalayas. Uplift is a continuous process as is weathering and erosion.
3.3 Passive
3.3.1 slide past eachother boundary between two plates pronounced by transform faults plates stick, friction builds, releases eqs
3.3.2 E.g. San Andreas Fault North America and Pacific plates, both moves NW But pacific moves faster (6CM TO 1CM)
3.4 Mark the site of major landforms.
3.5 mountain-building, volcanoes and earthquakes are found here
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