Restless Earth Flashcards
Oceanic
•oceanic Newer-less than 200ma Denser Can sink Can be renewed and destroyed
Continental
Older-over 1500ma
Less denser
Cannot sink
Cannot be renewed or destroyed
Types of boundaries
Constructive-build/make
Destructive-ruin/break it
Conservative-protect/keep things as they are.
Conservative
At conservative boundaries crust is neither created or destroyed as the plates move past each other
As the plates move at different speeds in slightly different directions they get stuck and pressure/friction is released suddenly an earthquake occurs
destructive
At destructive boundaries oceanic crust is destroyed as it is forced below the less dense continental crust. The melted rock forced its way to an area of lower pressure ready to erupt
Constructive
At constructive plate boundaries new oceanic crust is being made as the plates pull apart and magma rises to fill the gap and become solid rock
Collision boundaries
Plates move towards each other. As they are the same density one cannot be subducted . Pressure builds
Rocks are forced together and push up and fold to create fold mountains
Plenary
Fold mountains-collision/destructive boundaries
Ocean trenches-destructive boundaries
Composite volcano-destructive boundaries
Shield volcanoes-conservative boundaries
Ocean trenches
Located at destructive plate boundaries. They are created by subduction and mark the point where the oceanic crust is being pushed under the continental crust
Fold mountains and ocean trenchs
Both result from plates moving together. If both land forms occur in the same area they are doing in association with subduction. E.g. Destructive margins
Explain the formatting of ocean trenches
Plates that moved together form destructive plate margin which are forced together by convection currents. The oceanic crust is forced to sink below the continental crust which created a deep ocean trench. They are created by subduction
Fold mountains
Large mountains ranges where rock layers have been crumpled as they have been forced together
Composite volcanoes
A steep side volcano is made up of a varied materials such as lava and ash
Shield volcano
A broad volcano mostly made up of lava
Explain how volcanoes form at destructive plate margins
The oceanic plate goes under the continental plate because it’s more denser. The oceanic plate moves down the mantle where it’s melted and destroyed. This forms magma. The magma rises through the vents. The magma erupts onto the surface(lava) forming a volcano
Composite volcanoes
Made up of layers of ash and lava.
Steep sides
Usually erupt in an explosive way
Viscous magma rises to the surface-it clogs the vent and gas builds increasing the pressure-explosive eruption
Shield volcano
Made by lave that is very fluid-gentle slopes
Not explosive because there is little pressure building up
Effects of volcanic eruption
Disruption of flight
Damage to roofs
Damage to vehicles and communication systems
Damage to human health
Lahar
Created when snow and ice are melted again by a volcanic eruption
Flood damage to property
Expensive to clear form roads and farmland
Risk to human life
Pyroclastic flow
Massive cloud of hot gas and rocks which flows down the mountainside at up to 450mph with temperatures reached 1000d
30000 people were killed during an eruption in 1902 by the pyroclastic flow
Why are shields and composite different shapes
Shield volcanoes are less viscous so that the lava can spread out(expands out). Composite cysteine more viscous do that magma rises to the surface which increases the explosive eruption
Shield and composite
Composite volcanoes have sleep slows and narrow bases but shield volcanoes have a wide base and gentle slopes. Composite volcanoes are more viscous than shield volcanoes. Composite volcanoes erupt infrequent but often violent. Shield volcanoes erupt frequently and non-violent
Super volcanoes
A mega colossal volcano that erupt la at least 1000km3 of material
Super volcanoes 2
Much bigger scale than volcanoes
They are large depression called calderas
Often marked by a rim of higher land around the edges.
Super volcanoes erupt less frequently-eruption are hundred of thousands of years apart