Volcanoes Flashcards
where are most volcanoes found and why
at plate edges, because there is already a weakness at these points.
where is the ring of fire
the ring around the Pacific Plate
stretches from New Zealand through Indonesia, up to Japan joins North American Plate at Alaska, runs down on western side of United States towards Mexico and then down South American Plate.
what % of volcanoes and earthquakes occur in the ring of fire
- 90% of worlds earthquakes
- 75% of worlds volcanoes
can you draw or locate the ring of fire
yes / no
where can some volcanoes occur, why and how. give 1 example
some occur over hotspots because there’s a weakness / vent in Earth’s crust. gradually an island forms over hot spot and arises out of sea. For E.g Marion Island, where SA has weather station.
how do volcanoes occur
the heat in the mantle cause rock melt. this molten rock is magma. because Earth’s crust is cooling it’s contracting. the magma in mantle is therefore under extreme pressure. to release pressure magma forces its way through weaknesses that exist in Earth’s crust.
what are the 2 weaknesses in the Earth’s crust called
- holes called vents
- cracks called fissures
what is lava
it is magma that has reached the surface
what are the 2 different types of volcanoes and describe them
1 - some volcanoes erupt gently, with gentle lava flows that flow down volcano slopes
2 - others erupt violently spewing magma into air which forms ash cloud as some particles break up while large boulders are shot into air
how many people have the 2 types of volcanoes kill throughout the past 200 years
- almost 200 000 people
- both volcanoes are highly dangerous
can you draw and label a typical volcano
yes / no
learn 2 of the volcanoes in you book
how well do you know them
