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AQA paper 2 physical GCSE- The challenge of natural hazards
Terms in this set (20)
Plate tectonics theory
The theory is the earths crust is divided into slabs (tectonic plates) that float on the mantle.
What are the 3 plate margins ?
Destructive plate boundary
2 plates move towards each other. Oceanic plate meets continental, denser oceanic plate is submerged (destroyed and creates magma).
It forms volcanoes and ocean trenches.
It creates fold mountains.
Constructive plate boundary
When 2 plates move away from each other.
Magma rises from the mantle and cools creating a new crust.
Conservative plate boundary
where two tectonic plates slide past each other.
or moving in the same direction but at different speeds.
Crust isn't created or destroyed.
Why do the plates move ?
convection currents in the mantle
What is it called when the plates meet ?
Plate margins or boundaries.
Example of a destructive margin
The oceanic (Nazca - west coast of South America) meets the continental (South American plate)
Example of a constructive margin
The Eurasian place and North American plate.
How do earthquakes occur at destructive and constructive plate boundaries ?
- At destructive, oceanic plate moves down into the mantle, where it melts. A pool of magma forms, which rises through the cracks in the crust called the vents.
The magma erupts forming a volcanoes.
- At constructive margins, the magma rises up into the gap created plates moving apart, forming a volcanic.
What do volcanic eruptions emit ?
Lava and gas, ash.
What is a pyroclastic flow ?
Extremely fast moving ash, rock and gas that moves down the side of a volcano.
Distribution of earthquakes and volcanic eruptions.
Most earthquakes occur at the plate margins.
What is the jigsaw fit theory ?
Alfred Wegener the world was joined together as a single island called Pangea.
Continents fit like a jigsaw and wasn't proven until 1950 due to continental drift.
Evidence is that fossils matched from east of South America and west Africa had the same fossils.
Physical processes that take place at different types of plate margins that lead to earthquakes and volcanic activity.
- Destructive - tension builds up when one plate gets stuck and it moves past the other.
- Constructive - tension builds up along cracks in the plates and moves away from each other.
- Conservative - tension builds up when plates grind past each other get stuck.
- the plates eventually jerk past each other, sending out shock waves. (The vibrations are the earthquake)
- The shock waves spread out from the focus (the point where the earthquake)
- the waves are stronger at the focus and cause more damage.
- the epicentre is the point on the earths surface above the focus.
Types of natural hazard
Factors affecting hazard risk
Primary effects of tectonic hazards
Secondary effects of natural hazards
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