Restless Earth Flashcards
Describe continental crust
Think but less dense
How many major tectonic plates are there
Seven
How do destructive plate margins move
Towards each other
In detail what happens when the two plates move towards each other at a destructive margin
The lighter continental crust stays above but the oceanic crust goes underneath this is called a subduction zone
What does the rising magma cause at destructive plate boundaries
Composite volcanoes
Name the three land features of a destructive plate boundry
Fold mountains
Ocean trenches
Composite volcanoes
Why do earthquakes occur at destructive plate boundrys
Because energy build up in the subduction zone which forms and earth quake when the palates suddenly jolt under the pressure
How do constructive plate boundrys move
Away from each other
What fills up the gap at a constructive plate boundry
Magma
Where are constructive margins often found
Under the sea
What is formed at a constructive margin
Shield volcanoes
Why are islands sometimes formed at constructive margins
Because the shield volcanoe produces magma which solidifies above the water
What is the name for the margin in which the plates move across from each other
Conservative margins
What occurs at conservative margins
Earthquakes
What is the depression in which sediment forms to start the formation of a fold mountain
A geosyncline
What happens to the sediment in a geosyncline over time?
It turns to rock
What happens when pressure for plate movement is put onto the rock inside a geosyncline
It is forced upwards
What is the name for the tops of a fold mountain
Anticline
What are the dips of a fold mountain called
A syncline
Name the features of a shield volcano
5
Only made of lava Gentle slopes Wide base Regular eruptions Runny lava
Name the features of a composite volcanoe (5)
Made from ash and lava Steep slopes Shorter based Irregular eruptions Viscous lava
Where do earthquakes happen
At all margins
What is the focus
The underground centre of the earthquake
What is the epicentre of an earthquake
The point on the surface directly above the focus
What are shock waves
Waves of energy that move out in all directions from the focus
Describe the Richter scale with four points
Measured magnitude
Uses sismographs
They are logarithmic
Measure 1-10
Describe the mecaralli scale in three points
Measured by impact on people
Measured by human judgement
Measured in Roman numerals
Name three physical things that make an earthquake worse
Magnitude
Shallow focus
Ground eg sand is worse as it shakes more
Name four human factors that increase an earthquakes severity
Population density
Residential area
Self built housing
Lack of response
What could tsunamis be described as
The secondary effect of a earthquake at sea
How do tsunamis happen
One plate is stick under another causing tension
An earthquake occurs forcing the plate upwards
Sea rises causing water to be displaced and is pushed in a direction perhaps towards land
Describe oceanic crust
Thin but dense
