1.8 Plate Boundries Flashcards
What are the three types of plate boundries?
Convergent, divergent and conservative
What are the two convergent plate boundries
Continental - oceanic and continental - continental
Explain what happens at a convergent (continental-oceanic) plate boundry.
Two plates that are moving towards each other, the one that is denser will be submerged under the less dense
Give an example of a (continental-oceanic) convergent plate boundary stating which one subducts which.
The South American plate subducts the Nazca plate
What are the features produced at (continental-oceanic) convergent plate boundaries?
- Earthquakes
- Volcanoes
- Ocean trenches
- Tsunamis
Explain what happens at a convergent (continental-contiental) plate boundry.
The continental plate boundaries do not subduct but collide with each other and push upwards.
What is an example of a (continental-continental) plate boundary?
The Indo-Asian plate and the Eurasian plate.
What are features produced by (continental-continental) plate boundaries?
- Earthquakes
- Fold mountains
Explain what happens at divergent plate boundaries.
Two plates are moving apart, so magma fills the gap in-between the plates forming new crust.
Where are divergent plate boundaries mostly found?
Under oceans
What is an example of divergent plate boundaries?
The North American plate and Eurasian plate
What are the features produced at divergent plate boundaries?
- Earthquakes
- Volcanoes
Explain what happens at conservative plate boundaries.
Two plates slide past or next to each other which are moving at different speeds and angles, so they can become stuck which builds up pressure. When one of the plates break free this causes an earthquake.
What is an example pf a conservative plate boundary?
Pacific plate and North American plate
What are the 3 types of volcanoes.
- Composite
- Shield
- Hotspot
What are volcanic bombs?
Air borne material from a volcanic eruption.
What is a Lahr?
A destructive mudslide
What is the magma chamber of a volcano?
The source of the molten rock
What is a secondary vent of a volcano called?
A parasitic cone.
What are pyroclastic flows?
A flood of gas, dust and ash that moves rapidly down the side of a volcano.
Which plate boundaries are composite volcanoes caused by?
Convergent plate boundaries
What are composite volcanoes made of?
Alternate layering of lava and ash.
What type of lava do composite volcanoes have? (State the lava’s flow)
Andesitic lava (high silica content) - high viscosity. The lava flows short distances before cooling.
State the properties of the eruptions of composite volcanoes.
Violent but infrequent eruptions with lava bombs and pyroclastic flows.
Which plate boundaries are shield volcanoes caused by?
Divergent plate boundaries.
What type of lava do shield volcanoes have? (State the lava’s flow)
It has basaltic lava (low silica content) - low viscosity. The lava travels a long distance before cooling.
State the properties of the eruptions of shield volcanoes.
Frequent but relatively gentle with low explosivity.
What are hotspot volcanoes caused by?
Super heated rock in the mantle called plumes.
Explain the formation of hotspot volcanoes.
The plume rises from the hotspot to the mantle, as it reaches the asthenosphere and lithosphere, they melt. Magma rises through the crust and erupts onto the sea floor eventually forming a volcano.
What type of lava do hotspot volcanoes have? (State the lava’s flow)
Basaltic lava(low silica content) - low viscosity. The lava is thin, fast flowing, runny and travels far.
State the properties of the eruptions of hotspot volcanoes.
Low explosivity.
What are tsunamis caused by?
Earthquakes, volcanoes and landslides that happen on the ocean floor.
Explain how a tsunami is formed.
An earthquake, volcano or landslide displaces water vertically at the ocean floor which forms the start of the tsunami. As the tsunami approaches the shore it begins to slow down but grow in height and gain energy.
