Volcanoes Flashcards
What is a volcano?
A volcano is a vent or ‘chimney’ that connects molten rock (magma) to the earth’s surface. It includes the surrounding cone of built-up material.
Where are volcanoes generally found?
Generally and plate boundaries..
Constructive plate boundaries ( plates moving apart)
Destructive plate boundaries (oceanic crust moving towards continental crust)
Why do volcanoes erupt?
Volcanoes form when magma is forced up through the crust.
Gases can escape from the magma and create an explosion.
If there is solidified lava (a plug) blocking the way out, the magma and gases either force it out of the way or break out the side of the volcano.
Volcano at constructive and destructive plate boundary
Constructive margins - volcanoes form because the plates move apart and leave a gap that the magma can rise up into. Eruptions are quite gentle.
Destructive margins - the pressure building up creates explosive eruptions.
What happens at hotspots?
Volcanoes happen at hotspots.
These aren’t plate margins.
These are where there is a very strong upward convection current in the mantle which forces magma up through the crust to make volcanoes. Eg. Hawaii
How can you monitor a volcano?
Seismometer - to detect small earthquakes when magma is on the move.
Satellite images - to detect infra-red when the ground gets warmer days before an eruption as hot magma moves upwards.
Tiltmeter - to detect changes in the volcano’s slopes.
Global Positioning System (gps) - detects movement using satellite images.
What’s a lahar?
It is made of water (from melted snow or crater late) mixed with volcanic ash.
It follows river valleys.
Travels at high speed. Very dangerous
What’s pyroclastic flow?
A glowing cloud of red hot ash, rocks, steam and gases.
May move at over 200mph. Very dangerous
What are volcanic bombs?
Large rocks blown into the air by the force of the eruption.
They can crush and set fire to anything they hit.
What’s an ash cloud?
Can be blown a long way.
Can cause death my suffocation.
What’s lava?
Usually the last thing to be erupted.
Doesn’t flow far.
Not that dangerous.
Volcano benefits
-ash and dust, and any weathered rocks, produces fertile soil for farming.
-volcanic rocks used as building materials. Can produce valuable and rare minerals.
-tourists come to see the volcano bringing in sums of money from tourist trade.
-steam + hot water can be used to produce geothermal energy at no cost.
Tend to have lots of sea life close to produce more food.
Where is Mt. Merapi?
Located in a densely populated area in Central Java, Indonesia.
When did Mt. Merapi erupt?
It stated in late October, 2010, continued to erupt until 30th November 2010 and it officially ended on 3rd December 2010.
Why did Mt. Merapi erupt?
It was caused by the Indo-Australian plate being subducted beneath the Eurasian plate. It is located at a destructive boundary at a subduction zone.
