Tectonics - EQ1 Flashcards
At what boundaries are volcanoes mostly found?
Oceanic - Continental convergent
Oceanic - Oceanic divergent plate boundaries
What percentage of active volcanoes are found along the Ring Of Fire?
75%.
Name the statistics for earthquakes along the Ring Of Fire
80% of the world’s largest earthquakes.
90% of the world’s total earthquakes.
Name the 5 steps of a volcanic eruption
- Subduction of a tectonic plate
- Heat + pressure creates magma (molten rock).
- This plate has a lower density than the surroundings and so rises.
- Pressure + gas content build up in the magma chamber.
- Blockage is cleared with an eruption e.g Pinatubo 1991
What is the example of a volcanic eruption?
Pinatubo, Philippines-1991.
Name the 4 steps of an earthquake
- Plates move towards or slide past each other.
- Builds up tectonic strain.
- Pressure exceeds friction.
- Leads to a fracture- energy released as seismic waves=earthquake e.g Chile 2010, 8.8 magnitude.
Name the example of an earthquake
Chile 2010 - 8.8 magnitude.
Name 3 different types of plate boundaries
- Divergent
- Convergent
- Conservative
At which plate boundaries do lower magnitude earthquakes take place and why?
Divergent- less tectonic strain (usually between 3.0-5.0 magnitude e.g Iceland)
What are the 2 different plate combinations at a divergent boundary?
Oceanic - Oceanic
Continental- Continental
What happens at divergent plate boundaries?
New crust forms - earthquakes are formed by crustal stretching.
Name an example of an O-O divergent plate boundary
Mid-Atlantic Ridge.
Name an example of a C-C plate boundary
Rift valley between Nubian and Somalian plates.
What are the 2 possible plate combinations at convergent boundaries?
Oceanic - Continental
Continental - Continental
What are the 3 hazards situated at O-C convergent plate boundaries?
Earthquakes
Volcanoes
Tsunamis
Name an example of a location of an O-C convergent plate boundary
Ring Of Fire.
What are possible at C-C convergent plate boundaries?
Only earthquakes.
Name an example of a C-C convergent plate boundary
Indian and Eurasian plate - Fold mountains of the Himalayas.
Name an example of an earthquake at a C-C convergent plate boundary
Nepal 2015 - 7.8 magnitude.
Name the 2 possible combinations at conservative plate boundaries
Oceanic - Oceanic
Continental - Continental
What are possible at O-O conservative plate boundaries?
High magnitude earthquakes.
Possibly Tsunamis.
What are possible at C-C conservative plate boundaries?
Only high magnitude earthquakes.
Name an example of a C-C conservative plate boundary
San Andreas Fault - Pacific and North American plate.
Describe what happens to cause intra-plate earthquakes
- Pressure from all sides on the tectonic plate.
- Causes a reactivation of ancient rifts + faults.
- A fracture can occurs.
- Arguably more risky as perception of risk is lower - due to lower frequencies, therefore population are less prepared.
e.g Gujarat 2001 - 7.7 magnitude (20k deaths)
Name an example of an intra-plate earthquake
Gujarat 2001 - 7.7 magnitude (20k deaths).
Describe what happens to form intra-plate volcanoes
- A stationary mantle plume breaks through the thin oceanic crust to form a volcano and new crust forms.
- The oceanic plate is constantly moving and creates a volcanic island chain.
e.g Hawaiian Islands and eruption of Mount Kilauea in 2018.
Name an example of a volcanic island chain and a volcanic eruption
Hawaiian Islands.
Mount Kilauea in 2018.
