Plate Techtonics Flashcards
(27 cards)
What is the mantle made of and its state?
Made of silicate rocks
What part of the mantle is located just below the lithosphere?
The asthenosphere
What are the two parts to the core and their states
1) Inner core, solid, made of iron and nickel.
2) outer core, molten, made of iron and nickel
Explain how plates move?
1) Radio active decay in the mantle cause heat to be given off.
2) This creates convection currents in the Asthenosphere.
3) Convection currents create drag on the base of the plates causing them to move.
who and when proposed the theory for continental drift?
Alfred Wegener, 1912
How does geology provide evidence for plate tectonic theory?
Areas in South America and Africa have rocks that are the same age and composition, and the continents fit together. Suggesting they were once linked
How do Fossils provide evidence for plate tectonic theory?
Putting Continents together, the distribution of fossils matches up. e.g. A plant Fossil Glossopertris found over South America, Africa, India, Antarctica and Australia. Plants obvious could not swim this distance so these areas must have been close together.
How can Living species provide evidence for plate tectonic theory?
Many of the same species found over different Continent. That are unlikely to of swam or evolved in different locations. e.g. Earthworms.
How does Climatology provide evidence for plate tectonic theory?
Evidence that past climates were similar so suggesting continents were located closer together. Coal needs tropical environments to develop but is found in Antarctica and Europe.
2 Land forms created by constructive plate margins?
- Mid Ocean Ridge
2. Rift valley.
Explain how a mid ocean ridge is formed?
Under the sea when plates are diverging magma erupts through underwater volcanoes this magma cools and builds up creating a ridge e.g. mid Atlantic ridge
Explain how a rift valley is formed
when a plate is diverging it can create 2 parallel fracture lines. As the crust continues to move apart this chunk then fall down into the mantel creating the rift valley. e.g.
East African rift system
How is a deep sea trench formed?
Oceanic crust is subducted under continental crust. e.g. the Peru-Chile trench in the pacific Ocean
How are fold mountains formed?
Sediments accumulating on the oceanic crust whilst the oceanic is being subducted these pile up to form fold mountains.
Explain the formation of island ARCs
Oceanic crust is subducted under ocean crust, this creates friction below the surface, melting the crust forming lave. This lava travels to the surface and forms volcanoes these build up to for islands.
Define intrusive volcanic activity and 3 of its forms?
Volcanic activity that takes place below the surface, batholith, sills and dykes.
Define Extrusive volcanic activity?
Volcanic activity that takes place on the earths surface, major forms being volcanoes whilst minor forms tend to be hot-springs, geysers and boiling mud pools
What are the three types of lava and were would they be found?
- Basaltic, Constructive.
- Andesitic, Destructive
- Rhyolitic, Destructive
What is the Silica content, viscosity and temperature of Basaltic lava?
- Low
- Low (runny)
- high 1100 to 1200’c
What is the Silica content, viscosity and temperature of Andesitic lava?
- medium
- medium
- medium 750 to 950’c
What is the Silica content, viscosity and temperature of Rhyolitic lava?
- High
- High (thick and sticky)
- less than 750’c
Structure and lava type of a Dome volcano?
Central vent, lots of lava layers, steep sides. Made of Andesitic or Rhyolitic lava. e.g. Puy de Dome in France.
Structure and lava type of a Caldera volcano?
Central part of the volcano has collapse, the crater can be km wide. Rhyolitic lava. e.g. Aira Caldera in Japan
Structure and lava type of a shield volcano?
Gently sloping sides, central vent. Occurs at constructive margins or hot spots. Basaltic lava. e.g. Mauna Loa in Hawaii.
