Tectonic Processes and Hazards 1.1a, b&c PDF

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Summary

Edexcel A-Level Geography Year 1 | Physical Geography | topic: Tectonic Processes and Hazards | spec points: 1.1a, b&c...

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1.1 The global distribution of tectonic hazards can be explained by plate boundary and other tectonic processes. a. The global distribution and causes of earthquakes, volcanic eruptions and tsunamis.

Tectonic Hazards: ● Hazard ⇒ natural/geophysical event that has the potential to threaten both life and property ● Natural Hazards → hydro-meteorological, geophysical ● Hazards happen at either divergent plate boundaries, convergent plate boundaries or conservative plate boundaries

The Global Distribution of Hazards: ● Distribution of hazards is uneven → some areas of the world are at high risk and others are at low risk ● Earthquakes → along all types of plate margins ● Volcanoes → only at constructive and destructive plate margins. ● A lot of volcanic activity occurs in the ‘ring of fire’ ⇒ a group of volcanoes that are located along the plate margin of the Pacific plate ● Majority of tsunamis (over 90 per cent) → occur in the Pacific Ocean ● The oceanic fracture zone (OFZ) - a belt of activity through the oceans along the mid-ocean ridges, coming ashore in Africa, the Red Sea, the Dead Sea rift and California. ● The continental fracture zone (CFZ) - a belt of activity following the mountain ranges from Spain via the Alps, to the Middle East, the Himalayas to the East Indies and then circumscribing the Pacific.

b. The distribution of plate boundaries resulting from divergent, convergent and conservative plate movements (oceanic, continental and combined situations)

TYPES OF TECTONIC PLATES:

OCEANIC

CONTINENTAL

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makes up the ocean floor

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makes up the Earth’s landmasses

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High-density materials.

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Thicker (25-75 km) than oceanic plates.

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Made of basaltic rock.

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Less dense than oceanic plates

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Made of granitic rock

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Only 7-10 km thick. ●

Continental plates do NOT subduct

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Oceanic plates can subduct under other plates

TYPES OF PLATE BOUNDARIES: 4 main types: destructive, constructive, conservative, collision CONSTRUCTIVE

DESTRUCTIVE

CONSERVATIVE

COLLISION

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Plates diverge

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Oceanic plate slides beneath the continental plate

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Plates are sliding past each other horizontally

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Two oceanic plates/continental plates move towards each other

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Convection currents push apart and cause a gap between the plates

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Crust is destroyed as one plate dives under another at the subduction zone

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The plates, made of rock that has jagged edges, catch and snag against one another

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Layers of sedimentary rock on the seafloor become crumpled and folded

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Magma rises to fill up the gap created

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Rocks catch against each other as the plates are not smooth

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Friction and pressure between the plates builds until the plates can't take the stress

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Eventually, the sedimentary rock appears above sea level as a range of fold mountains

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New crust generated as plates pull

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The pressure between plates builds until the

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Plates slip past each other causing

away from each other shield volcanoes aka Divergent

plates can't take the stress

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The plates slip past each other, which can cause both plates to move resulting in the ground shaking

both plates to move to result in the ground shaking aka Transform

aka Convergent

c. The causes of intra-plate earthquakes, and volcanoes associated with hot spots from mantle plumes Causes of INTRA-PLATE EARTHQUAKES: ● Earthquakes can happen in mid-plate settings ● Plates have a pre-existing weakness that becomes reactivated by tectonic stresses, forming seismic waves ● Zones of weakness are created as plates move and stress increase HOTSPOTS: ● ⇒ hot mass of rising heat under weakness in a plate ● Magma rises to the surface through this weakness Causes of INTRAPLATE VOLCANOES: ● Volcanic hotspots: (Ring of Fire) - a localised area of the lithosphere which has an unusually high temperature due to the upwelling of hot molten material from the core ● Isolated plumes of convecting heat (mantle plumes) rise towards the surface generating basaltic volcanoes. ● The plume remains stationary, although the tectonic plate above moves slowly over it. ● Continuing plate movement over time produces a chain of volcanic islands, with extinct ones furthest from the plume location...