Tectonics Flashcards
What is a natural hazard?
A natural hazard is an event that threatens people or has the potential to cause damage, destruction and death.
If an HIC is impacted it will cope better because:
- government stable + democratic + has agencies to help in emergencies
- technology can predict events e.g USA has USGs. Technology can protect buildings.
- Planning laws prevent buildings in dangerous areas
- Agencies that can act quickly to help an area e.g army, fire crew
- Better education
What are the 4 layers of the earth (inside to out)?
- Inner core
- Outer core
- Mantle
- Crust
What are convection currents?
They take place in the mantle where the hot core causes magma to rise in the mantle and sink back down to the core when it cools. Convection builds pressure and carries the plates with it.
What is slab pull?
The denser plate sinks back into the mantle under the influence of gravity. It pulls the rest of the plate along behind it.
What is ridge push?
Magma rises as the plates move apart. The magma cools to form a new plate material. As it cools it becomes denser and slides down away from the ridge. This causes the tectonic plates to move away from each other overtime.
What is continental drift?
The movement between land/continents.
What is the proof for continental drift?
The apparent fit of continents, the correlation of fossils on earth, the rock and rock type correlation, paleoclimate data.
Which boundary type is divergent?
Constructive
Which boundary types are conservative?
sideways or transform
Which boundary types are convergent?
Destructive or collision
Describe a destructive plate boundary:
It is found where convection currents push a continental plate and oceanic plate towards each other. The oceanic plates subducts under the continental because it is denser. Where two plates intersect a deep trench forms. Earthquakes occur at varying depths along the subduction zone where the lates stick and pressure builds up. When the plate has descended below 100km it starts to melt due to rising temperature and pressure as it moves into the mantle. The magma is now less dense than the surrounding rock and rises through the gaps in the continental plate. Most of the molten rock cools and solidifies in huge sponge-like magma chambers far below the Earth’s surface. If it reaches the surface, there is an explosive eruption of gases, ash and lava.
Describe a constructive plate boundary:
It is found where two plates move apart and a new crust is formed at the boundary. The plates are being pulled apart through convection currents. Initially rift valleys form on sea floor. Magma rises from the mantle to fill the gap between the separating plates forming submarine volcanoes which in time may grow above sea level. A midge ocean ridge develops at this point. As the basaltic magma cools it adds new land to separating plates.
Describe a conservative plate boundary:
They occur where two plates move parallel or nearly parallel to each other. Crustal roc are neither created or destroyed here. The boundary between the plates is characterised by pronounced transform faults. As the plates move past each other they stick building pressure. Suddenly when there is a release of pressure the plate jerks forward and energy is released in the form of seismic waves causing an earthquake.
Describe a collision plate boundary:
Two continental plates move towards each other and collide. Neither plate can be created or destroyed here so they are forced upwards or downwards. The upwards section makes fold mountains and the downwards section makes mountain roots. There are high magnitude earthquakes at collision plate boundaries because of the massive build up of friction and pressure. However no plate is being destroyed. magma is not created, so no volcano formed.
Example of destructive plate boundary:
Nazca plate subducts under south American
