3.1.5.2 Plate Tectonics Flashcards
What are constructive plate boundaries?
Where two plates are moving apart (diverging).
New crust forms where rising plumes of magma stretch the crust and lithosphere.
You can have continental-continental or oceanic-oceanic.
What does constructive continental-continental plates form? (3)
- Earthquakes
- Rift valleys
- Volcanoes
What does constructive oceanic-oceanic plates form? (3)
- Earthquakes
- Ocean ridges
- Volcanoes
What does destructive continental-continental plates form? (2)
- Deep Earthquakes
- Young fold mountains
What does destructive oceanic-oceanic plates form? (4)
- Ocean trenches
- Island arcs
- Earthquakes
- Volcanoes
What does destructive continental-oceanic plates form? (3)
- Earthquakes
- Volcanoes
- Deep sea trench
Constructive plate vulcanicity characteristics
The moving apart of the plates release pressure in the mantle causing it to melt creating magma. This is less dense and rises resulting in an eruption (forming volcano).
Basaltic lava is formed here - very hot and has a low viscosity (runny).
Eruptions of basaltic lava are frequent and go on for a long time.
The eruptions are not very violent.
Destructive plate vulcanicity characteristics
Subduction results in volcanic activity.
Andesitic any rhyolitic lavas are formed when oceanic crust dips below continental crust and melting occurs - cooler and more viscous (less runny).
These lavas usually erupt intermittently.
Because the lava is viscous it forms blockages in volcanic vents causing pressure to build. This leads to violent eruptions.
Constructive plate seismicity characteristics
Parts of plates don’t move at the same speed leading to pressure being built up.
When the pressure becomes too much, the plates crack causing a fault line and causing an earthquake.
Destructive plate seismicity characteristics
The subduction of a plate causes massive pressure to build up causing a huge earthquake when it is released.
The biggest earthquakes occur at destructive margins where one plate is forced beneath another at the subduction zone.
What are destructive plate margins?
Where two plates are moving towards each other (converge).
Also referred to as subduction zones and as it is here that lithosphere is destroyed.
You can have continental-continental, oceanic-oceanic, continental-oceanic.
What are conservative plate margins?
A conservative plate margin occurs where two plates are moving past each other.
Conservative plate seismicity characteristics
The two plates get locked together.
Pressure builds up.
This causes the plates to jerk past each other or crack, causing fault lines, releasing the energy as an earthquake.
Example: San Andreas fault line (California)
