Flashcards
Restless Earth
Cards in this deck (13)
- 1What are some features of oceanic crust?Sima
Newer, usually <200 million years old
Denser
Can sink
Can be renewed and destroyed
6-10 km thick
Basaltic composition
Silica and magnesium - 2What are some features of continental crust?Sial
Older, mostly >1500 million years old
Less dense
Cannot sink
Cannot be renewed or destroyed
35-40 km thick
Silica and aluminium - 3What are geosynclines?A depression into which sediment settles and which then goes on to form fold fountains when two plates move together.
- 4What are the characteristics of composite volcanoes?Formed from mixed layers of lava and pyroclastic debris
Steep slopes and narrow base
Eruptions infrequent but often very violent with pyroclastic flows and lahars. - 5What are characteristics of shield volcanoes?Wide base and gentle slopes
Layers of runny lava, with little ash
Low, rounded peak
Eruptions frequent and non-violent - 6How can volcanic eruptions be predicted?--Seismometers used to detect small earthquakes caused as magma forces its way up through cracks in the earth's crust
--Thermal imaging can pick up temperature rises around a volcano as activity increases
--Gas released from volcano sampled and chemically analysed for sulphur content. High levels of sulphur=close to eruption
--Building hazard maps from historical information - 7Name two examples of volcanoes that are closely monitored at all times.Mount St Helens in USA
Mount Etna, Italy - 8How can an area prepare for an eruption?--Have a detailed plan which everyone who could be affected knows well
--Exclusion zone around volcano
--Ability to evacuate quickly
--Emergency provisions of food
--Good communications
--Use of hazard maps - 9What are the characteristics of supervolcanoes?--Tend to sit on large hotspots
--Emit at least 1000 cubic km of material
--Look like large depressions (calderas) - 10In which ways can the strength of earthquakes be measured?--Richter scale: logarithmic scale, measures vibrations
--Mercalli scale: measures effects of an earthquake - 11At which plate boundaries do: 1) earthquakes happen 2) volcanoes form1) destructive, constructive, conservative
2) destructive and constructive - 12How can the impact of earthquakes be reduced?Prediction: difficult, foreshocks occur but on too short a timescale; some think animal behaviour can be used
Protection: earthquake resistant buildings
Preparation: disaster drills; codes of practice - 13How do tsunamis differ from normal waves?Normal wave 100m crest to crest; tsunami 200km
Normal wave 2m high; tsunami 1m
Normal wave speed 40 km/h; tsunami 800 km/h
As tsunamis near land, they reduce in length and increase in height, to around 30m
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- GCSE Geography (Restless Earth) Flashcards on Restless Earth, created by muon neutrino on 05/04/2016.
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