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Plate Tectonics
and Associated
Hazards:
Revision Pack





Zoe Leek

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Contents
I. Theory of Plate Tectonics
i. Geological Evidence
ii. Biological Evidence
iii. Earth's layers
II. Plate Margins
i. Constructive
(ia) Oceanic Ridges
(ib) Rift Valleys
III. Hotspots
IV. Vulcanicity
i. Volcanic eruptions
V. Intrusive landforms
i. Batholiths/laccoliths
ii. Dykes
iii. Sills
VI. Extrusive landforms
i. Basaltic lava
ii. Andesitic/rhyolitic…

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(if) CS: Lake Nyos




Plate tectonics and associated hazards


In 1912 a German, Alfred Wegener, published his theory that a single continent existed about 300 million years ago. He names
this super ­ continent Pangaea, and maintained that it had later split into the two continents of Laurasia in the…

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Sea floor spreading implies that the Earth must be getting bigger. As this is not the case, then plates must be being destroyed
somewhere to accommodate the increase in their size at the mid ocean ridges. Evidence of this was found with the discovery of
huge oceanic trenches where large…

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Constructive (divergent) margins

Where plates move apart in oceanic areas they produce midoceanic ridges. Where they move apart in continental crust, they
produce rift valleys. Constructive margins are therefore some of the youngest parts of the Earth's surface, where new crust is
continuously being created.

Oceanic ridges

Oceanic ridges are…

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is causing the plate to thin as it starts to split. The line of the African rift is thought to be an emergent plate boundary, the
beginning of the formation of a new ocean as eastern Africa splits away from the rest of the continent.

Divergent (convergent) margins

There are…

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The plates forming continental crust have a much lower density than the underlying layers, so there is not much subduction
where they meet. Instead, as the plates move towards each other, their edges and the sediments between them are forced up
into fold mountains. As there is little subduction, there…

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Vulcanicity is normally associated with plate margins but, in the centre of the Pacific Ocean, we find the volcanic Hawaiian
Islands that are not connected with any plate boundary. It is believed that this volcanic area is caused by a localised hot spot
within the pacific plate. A concentration of…

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Not at plate boundaries Hot spots: may be neat the Plume volcanoes Hawaiian islands: Emperor
centre of a plate seamount chain






Most volcanic activity is associated with plate tectonic processes and is mainly located along plate margins. Such activity is
therefore found;

Along oceanic ridges where plates are moving apart.…

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Dykes

Dykes are vertical intrusions with horizontal cooling cracks. They cut across the bedding planes of the rocks into which they
have been intruded. Dykes often occur in groups where they are known as dyke swarms. Many Scottish islands such as Mull
and Skye, have clusters of dykes, all associated…

Comments

Isobella98

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this is soooooo useful, thankyou for sharing :)

Muturi1

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Very comprehensive, helpful and high standard- done notes. Well done Zoe and Thank you!!! for sharing this resource.

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