TECTONICS: types of plate boundaries Flashcards
What happens at Constructive (divergent) boundaries?
- Earthquakes tend to be mild and shallow
- Eruptions tend to be small and effusive
- The eruptions are usually of basalt lava:
Low gas content
Low viscosity
Higher temperature
What happens at Destructive (convergent) & Collision (convergent) boundaries?
- Friction and pressure build up in the Benioff zone (the area within the subduction zone where most friction and pressure build up occurs) causes strong earthquakes
- Volcanic eruptions tend to be explosive as the magma is forcing its way to the surface
- These eruptions are often rhyolite lava:
High gas content
High viscosity
Lower temperature
What happens at Transform (conservative) boundaries?
Plates can stick causing a significant build up of pressure and powerful earthquakes
Convergent (destructive)
- 2 plates move together
- desner plate subducted and melts in mantle
Convergent (destructive)
Earthquakes:
- largest and most damaging
- as stress builds in the subduction zone
EXAMPLE: Japan 2011 Earthquake & Tsunami, Nepal 2015 Earthquake
Volcanoes:
- create large proportion of the Earth’s active volcanoes
- most explosive types
- less frequent but more destructive
Conservative plate boundary
- plate slides against each other
- lithosphere is neither created or destroyed
Conservative plate boundary
Earthquakes:
- create shallow focus earthquakes
- can be very destructive
EXAMPLE: Los Angeles 1994 Earthquake
Volcanoes:
- do NOT cause volcanic activity
Divergent (constructive) plate boundary
- 2 plates move apart from each other
- leads to creation of crust
- mostly clearly displayed at mid ocean ridges
Divergent (constructive) plate boundary
Earthquakes:
- frequent
- low risk seismic activity
- doesn’t normally cause tsunamis
Volcanoes:
- rift volcanoes are created
- less explosive
- more effusive especially deep underwater
