The Restless Earth Flashcards
(43 cards)
5 features of continental plates
Older
Thicker
Less dense
Lighter
Convection Current
Heat rises from the core and travels through the mantle. The heat comes as a result of radioactive decay in the core. The movement of plates are as a result of convection currents
Constructive Plate Boundaries + example
The two plates are moving apart due to the convection currents in the mantle.
In the North Atlantic Ridge, the two oceanic plates (Eurasian and North American) are slowly moving apart. Magma rises up from the mantle and cools to form a new crust. Sometimes the magma reaches the surface and forms islands such as Iceland.
Conservative Plate Boundary + example
The two plates are moving past each other. The friction that occurs leads to very strong earthquakes because is has a shallow focus. The San Andreas fault between San Francisco and Los Angeles
How do earthquakes occur
One plate catches on the other when it is moving adjacent to it or sub ducting beneath it. The plates catch and the pressure builds up. As the pressure builds up from friction, it releases eventually and the jolt of the plates leads to the earthquakes
Destructive plate boundary + example
Oceanic plate subducts beneath the continental plate. The plate subducts into the subduction zone where the oceanic plate melts in the mantle. Excess magma is forced up through weaknesses in the crust. Earthquakes occur in the zone between the two plates where they touch.
Peru - Chile trench
How are fold mountains formed
O+C
Continental plate collides with oceanic plate. The oceanic plate subducts beneath the continental and the continental plate continues to move in the same direction and buckles
Structure of the Core
Solid inner core
Liquid outer core - iron and nickel
Mantle - soft molten rock
Crust - hard outer shell
Shield Volcanoes Location
Constructive plate boundaries such as Iceland
Shield Volcanoes nature of lava
Runny and therefore flows a long way. Creates wide cones with shallow sides
Shield Volcanoes nature of eruption
Magma isn’t viscous so releases its gases beforehand therefore no pressure build up
Not explosive yet frequent eruptions
2 examples of Shield Volcanoes
Mauna Loa in Hawaii
Emi Koussi in Chad
Description of a shield volcano
Much wider than tall. (120km vs 8km)
Long sloping sides
Layers of lava and stone inside them
Large magma resevoir
Composite Volcanoes location
Destructive plate boundaries
Composite Volcanoes nature of lava
Sticky and viscous lava so steep sided mountains
5 features of Oceanic Plates
Newer Thinner Denser Heavier 6-10km thick
Composite Volcanoes nature of eruption
Top blown off
Hail of ash and rock
Lots of steam
Quiet
2 examples of Composite Volcanoes
Mount Fuji - Japan
Mount Rainer - Washington
Description of Composite Volcanoes
Steep sides due to slow flowing lava
Layers of hardened lava
Crater at top
Subsidiary cones
Formation of fold mountains
C + C
Thick sediment layers form in huge depressions called geosynclines under the sea
Over the years the sediments are compressed into rock
As the plates move towards each other, the sedimentary rock is compressed and buckles upwards
Why are ocean trenches of little use to humans
Too deep for humans to reach the ocean floor
On,y possible for short times using expensive machinery
Three economic positives of tourism in fold mountains
4% of Nepal’s GDP is from tourism ($500m) - 50k per trip
$3.3m from people climbing Everest each year
£1600 earned by each Sherpa per trip
Three social positives of tourism in fold mountains
Funds contribute to communities (school, hospitals)
Financial support for preservation of environment
Can educate rest of the world on other religions
Two environmental positives of tourism in fold mountains
Must collect 8kg of litter or £4000 fine
Money earned used to preserve fragile environment.
