what happens at plate margins Flashcards
what is the earth made up of
the earth is made up of layers
what are the layers of the earth called
solid core (solid/hard due to the great pressure on it), outer core (liquid), mantle (made up of liquid magma- this escapes from cracks in the earth eg. volcanoes), crust (can be divided into 2 types- oceanic crust that is under oceans and the continental crust which forms the continents)
what are the properties of the continental crust
it is thick, older than the oceanic crust, and light
what are the properties of the oceanic crust
it is thin, younger than the continental crust, and heavy
what happens at constructive plate margins
2 plates move apart from each-other. as they love a gap is created in between them. this allows magma to escape through the gap as lava, either as a gentle eruption or as a lava flow. the lava creates a new oceanic crust. an example of a constructive plate margins is the mid-Atlantic ridge
there is earthquakes and volcanic activity here
what happens at destructive plate margins
oceanic crust and continental crust are moving together, as the oceanic crust is heavier than the continental crust, it is forced downwards. every time the oceanic crust moved down, earthquakes occur. whenever the magma escapes, huge eruptions can occur. an example is the nazca plate forcing under the south american plate
there is earthquakes and volcanic activity here
what happens at conservative plate margins
2 plates slide past eachother, as they go past eachother they stick. pressure builds up and when it is finally released, a very severe earthquake occurs. no crust is destroyed or created so there is no volcanic activity. this happens frequently at the san andreas fault in california with the north american and pacific plates. it can include oceanic or continental crust
there is earthquakes here
what happens at collision margins
2 plates move towards eachother. the crust is always continental. they can’t sink or be destroyed so they touch eachother and push the plates up. this creates ‘fold mountains’. an example of this margin are the himalayas
there is earthquakes here
what is the pacific ring of fire
it is a ring from the west coasts of america to indonesia and japan and this is where there is lots of volcanic activity and earthquakes. the anomaly is mauna loa which lies right in the middle of the ring of fire.
what are products of volcanic eruptions
ash, pyroclastiques flow, rocks, gases
what are active, dormant and extinct volcanoes
an active volcano is a volcano that has erupted recently and is expected to erupt again
a dormant volcano is a volcano that has erupted in the last 2000 years but not recently
an extinct volcano is a volcano that is not expected to erupt again
what are the 2 types of volcano
strato volcanoes - they are steep sided, tall and pointy. they are big and tall. the lava is viscous(thick) and flows slowly. gas pressure builds up causing an explosion.
shield volcanoes - they are gently sloping, wide and short. the lava is fluid and flows quickly. there are lava flows
how do you monitor and predict volcanic eruptions?
smell of sulphur, smoke, rocks fall off, seismic activity, lots of small earthquakes, frequent lava flow, temperature - thermal imaging
what is an earthquake
it is the shaking and vibration of the crust due to movement of the earths plates (plate tectonics)
what is pressure and what is tension
pressure is a build up of energy and tension is the release of energy
