Volcanoes Viola 5/6 A

What is a volcano?

A volcano is an enormous moutain with a hole in the top. TIP: there are 1500 volcanoes in the world. A dormant volcano has not erupted in a long time but there is a possibility that it will erupt in the future.

How are volcanoes formed?

Volcanoes form when magma from within the Earth's upper mantle works it's way to the surface. At the surface, it erupts from lava and ash deposits. Over time, as the volcano continues to erupt, it gets bigger and bigger.

Why do volcanoes erupt?

The Earth's crustis made up of huge pieces called plates, which fit together, just like a puzzle. These plates sometimes move. The friction sometimes causes earthquakes and volcanic eruptions near the edges of the plates. The theory of this progcess is called plate tectonics.

What are plate tectonics?

The theory of plate tectonics is an interesting story of continents drifting apart, grinding against each other. The plate tectonic theory is supported by a wide range of evidence that considers the Earth's crust and upper mantle to be composed of several large, thin, rigid plates that move relative to one another. The plates are all moving in diferent directions and at diferent speeds. Sometimes the plates crash together, pull apart or sideswipe aech other. When it happens, it commonly results as earthquakes.

How many volcanoes are there?

There are more than 1500 volcanoes on Earth. We currently know about 80 or more, which are under the oceans. Active volcanoes in the U.S. are found mainly in Hawaii, California, Orgeon and Washington.

What are the different types of volcanoes?

Volcanoes are grouped into four types: cinder cones, composite volcanoes, shield volcanoes and lava volcanoes.

What are the difference between lava and magma?

Magma is liquid rock inside a volcano. Lava is liquid rock (magma) that flows out of a volcano. Fresh lava glows red hot to white hot as it flows.

Why does lava take a long time to cool down?

Lava cools slowly because lava is a poor conductor of heat. Lava flows slow down and thicken as they harden.

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