Tectonic plate boundaries and features
- Created by: EEC2145
- Created on: 27-01-23 14:40
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- Plate boundaries
- Convergent
- Oceanic-Oceanic
- Caribbean plate + South American plate
- Puerto Rico Trench (8.6km deep, 280km long)
- One plate (older one) is subducted under the other causing the other to bend, forming a v-shape between them
- Puerto Rico Trench (8.6km deep, 280km long)
- Ocean trenches
- One plate (older one) is subducted under the other causing the other to bend, forming a v-shape between them
- Obduction
- The sea floor sediments are scraped off the subducted plate (South American) forming an accretionary wedge on the other
- Subduction
- As the plate is subducted the sea water evaporates lowering the melting point of the mantle, producing magma
- This then causes explosive volcanic eruptions
- As the South American plate is subducted it causes friction against the Caribbean plate... Earthquakes!
- Benioff zone
- Where many earthquakes occur from the subduction
- Benioff zone
- As the plate is subducted the sea water evaporates lowering the melting point of the mantle, producing magma
- Andesitic lava
- 1000*C
- Viscous
- Produces pyroclastic flows e.g. Monserrat 1990s
- Caribbean plate + South American plate
- Oceanic-continental
- Nazcan plate + South American plate
- Off the coast of Chile
- Oceanic is forced under the continental
- Shallow focus earthquakes in the Benioff zone.
- Accretionary wedge
- Formed from the obduction off the oceanic plate
- Subducted plate melts causing andestic lava
- Very explosive eruptions
- Lascar in Chile
- Small amounts of lava, lots of ash
- Viscous, trapping gas bubbles making it hard for them to escape
- Very explosive eruptions
- Andes
- Nazcan plate + South American plate
- Continental- continental
- Indian plate and Eurasian plate
- Himilayas
- Formed from the obduction off the oceanic plate
- Himilayas
- No subduction as both plates are of equal density
- Crustal shortening
- The 2 plates collide and as neither is subducted they "fold" up making the crust thicker in that area
- Himilayas
- Andes
- Himilayas
- The 2 plates collide and as neither is subducted they "fold" up making the crust thicker in that area
- No volcanic activity as no plate is subducted under the other
- Any magma that does rise solidifies before it reaches the surface of the thickened crust
- Crustal shortening
- Shallow focus earthquakes as the 2 plates are still moving into each other
- Indian plate and Eurasian plate
- Oceanic-Oceanic
- Divergent
- Continental
- Afar region, Arabian, Somalian and Nubian plates
- Red Sea is formed from the Arabian and African plates moving apart
- Causing the area between them to become a graben that dropped below sea level
- Indian Ocean then flooded it forming the Red Sea
- Causing the area between them to become a graben that dropped below sea level
- Dead Sea in Israel is the lowest point on the continental surface (-400m)
- Plates here are moving due to a hotspot (rising mantle plume) forcing the plates to rise and split which separates them
- Red Sea is formed from the Arabian and African plates moving apart
- The crust is uplifted and stretched causing a sunken valley (graben or rift valley)
- Earthquakes
- Flood basalts
- A hotspot causes the lithosphere to stretch and fracture causing lava to pour out, the lava the forms the flood basalt
- Afar region, Arabian, Somalian and Nubian plates
- Oceanic-oceanic
- Transform fault
- A break in the mid-ocean ridges
- Earthquakes as the faults displace the ridge and energy is released as an earthquake
- Mid-ocean ridges
- Rate of spreading is determined by the amount and rate of rising magma
- Mountain chains are found along them
- 3000m above the sea bed in some places
- They have a combined length of 60,000km
- Pillow lava
- Rounded mounds formed by magma erupting directly onto the sea bed and cooling instantly
- Black smoker
- A hydrothermal vent
- Sea water seeps into rifts and is super heated, re-emerges on the ocean floor containing metal sulphides
- Underwater rift valley
- Rigid lithosphere is put under stress and fractures, a block of rock drops down
- Transform fault
- Continental
- Convergent
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