Volcanoes Flashcards
what is a volcano?
A mountain or hill that has an opening at the top through which lava, pieces of rock, ash and gases erupt
How many volcanoes in the world are currently active?
Between 50 and 70
Where are many of the volcanoes located?
Around the edges of the Pacific Ocean:
. The west coast of the Americas
. The east coast of Siberia, Japan, the Philippines and Indonesia
. In island chains from New Guinea to New Zealand - the so-called ‘Ring of Fire’
Recently, active volcanoes were also found in Iceland, the Kenya Rift Valley in Eastern Africa, Italy and Hawaii. When we look at the locations of the world’s most active volcanoes, we can see that most of them occur near the edges of the large tectonic plates
What does it mean for a volcano to be dormant?
Not active at the moment
What are hot spots?
Volcanic regions where there is a lot of volcanic activity
What causes hot spots?
The mantle in these areas is much hotter than in other areas
Where can you find hot spots?
They may be on, near to, or far from tectonic plate boundaries
Give an example of a famous hot spot.
The Hawaiian hot spot that has produced a volcanic chain that extends 6000km across the northwest Pacific Ocean
What is the ring of fire?
An area where a large number of earthquakes and volcanic eruptions occur in the basin of the Pacific Ocean
How many volcanoes are there in the ring of fire?
452, which is over 50% of the world’s active and dormant volcanoes
What else occurs in the ring of fire?
About 90% of the world’s earthquakes and 81% of the world’s largest earthquakes
Why are there so many volcanoes (and earthquakes) in that area?
The tectonic plates in this area move and collide nearly continuously. For example, in the eastern section of the ring the Nazca Plate and the Vocos Plate are continuously colliding with the westward moving South American Plate and sliding beneath it
Why do volcanoes occur?
When tectonic plates collide, one plate can slide under the other. This can cause the mantle underneath to melt and become magma. The magma pushes upward through the cracks and weak points in the crust, melting more rock. The hot magma collects under the surface of the Earth in magma chambers. In addition, it is so hot deep inside the Earth that some rocks slowly melt and become magma. Because magma is lighter than the solid rock around it, it rises and and also collects in magma chambers. When the pressure is high enough in the magma chamber, or if a crack opens in the crust, the magma is forced up the vent and shoots out through the crater
What are the three basic kinds of volcanoes?
Shield
Cinder cone
Composite
