Geography Edexcel paper 1 - Tectonics EQ1 - Why are some locations more at risk from tectonic hazards

What 2 factors do plate motion depend on?

-The weight of the cold plates at the subduction zone pulling the slab downwards

-Gravitational sliding where the weight of the slab begins to subside(become less violent) into the mantle to compensate for the increase in density of the slab

Describe destructive/convergent plate margins(means the same as boundary)

-Oceanic plate moves towards continental plate

-The heavier denser oceanic plate is subducted (where one tectonic plate moves under another and sinks into the Earth's mantle) beneath the lighter continental plate

-As it’s forced downwards pressure at the margins increases and results in violent earthquakes/volcanoes

e.g CHILE subduction of the Nazca Plate beneath the South American Plate, which creates the Andes Mountains

Villarrica (Southern,Chile) Known for its persistent lava lake and frequent, mild-to-moderate explosive activity

Describe Constructive/Divergent Plate margins

-The earth’s crust is forced apart

-Magma rises and solidifies to create a new oceanic crust and forms a mid-ocean ridge(underwater mountain system)

-The ridge is made from igneous rock and such ridges usually form below sea level

e.g ICELAND Mid-Atlantic Ridge

Describe collision plate boundaries (Type of convergent/destructive)

-When 2 plates moving together are both made from continental crust

-Continental crust can’t sink or be destroyed as a result the land between them is pushed upwards to form high fold mountains

-Earthquakes are common but no volcanoes (because there is no subduction)

e.g NEPAL The himalayans

Describe conservative/transform plate margins

-2 plates sliding past each other slowly

-often these stick and pressure builds up,the release of this pressure creates a severe earthquake

-Conservative/transform plates margins have no volcanic eruptions because the crust is being neither created nor destroyed

-However because they are close to surface they can be more violent EQ’s

Examples - haiti/New zealand -christchurch

What is a hot spot plume?

A stationary, upward current of unusually hot magma rising from deep within the Earth's mantle that create volcanoes on the surface.

How do hot spot plumes work?

-The tectonic plate above the plume is constantly moving, typically due to convection currents in the mantle.

-As the plate moves, the magma plume burns through weaker parts of the crust, creating a volcano.

-The new volcano is active, but as the plate moves, it is carried away from the plume. A new volcano forms over the hotspot, and the older one becomes dormant. This process repeats, creating a chain of volcanoes, like the Hawaiian Islands.

What are the key characteristics for a hot spot plume?

• Location: Hot spots are not at plate boundaries, unlike volcanoes that form at convergent or divergent plate margins.

• Activity: The volcano directly above the hot spot is active, while those that have moved off the plume are dormant

• Age: The further a volcano is from the hotspot, the older it is. (the volcanoes farther away are older because they formed earlier in the plate's history.)

Have convection currents been disproven?

Yes because:

-heat generated from convection isn’t enough to pull the plates - not forceful enough

-The slab pull theory suggests that plates are pulled down through gravitational sliding

However,they are useful for explaining hot spot plumes

Why do we have tectonic plates?

due to heat generated from the earth’s core by radioactive decay