Volcano FactsVolcanoes are openings in the surface of the Earth from which gas and hot molten, or liquid, rock escape and cover the surrounding land.
Some volcanoes are simply long cracks in the ground. Others look like cone shaped mountains with a hole in the top. The hole is called a vent.
When molten rock is inside the Earth, it is known as magma. But when it escapes onto the Earth's surface, it is called lava. As lava flows, it cools and hardens. The hardened lava, as well as ash and cinders from the volcano, pile up around it to form a cone shape.
A volcanic eruption is a spectacular and often terrifying sight. Red-hot lava may burst out of the volcano with a deafening roar creating beautiful but deadly fire fountains of glowing lava which shoot hundreds of metres into the air.
Lava is either very runny, or stiff and thick. Different volcanoes produce these different lava types. But some volcanoes produce no liquid lava at all. Instead they shoot out solid pieces of rock.
On average, between 20 and 30 volcanoes erupt each year.
Mauna Loa on Hawaii is the largest live volcano on Earth. One eruption lasted for one and a half years!
Stromboli, a volcano off the coast of Italy, erupts once every 20 minutes! It's known as the lighthouse of the Mediterranean.
Throughout history people have lived near volcanoes. This can be dangerous, as in 1883 when the volcanic island of Krakatoa in Indonesia exploded. The explosion killed 36,000 people on or near the island.
Volcanoes are either live or dead. A live volcano is one that may erupt in the future. A dead volcano is one which erupted in the past but will not again. When a live volcano is erupting, it is said to be active. When it is not erupting it is said to be dormant.
Volcanoes usually occur in places where the earth's plates meet, and magma rises from underground.
At least eighty active volcanoes are known to be on the bottom of the sea. Sometimes when they erupt their cones burst above the sea to create islands.
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