Tuesday, September 18, 2007

Offbeat Tuesday

There are more than 1500 active volcanoes on the Earth. We currently know of 80 or more which are under the oceans.

The Earth's crust is made up of huge slabs called plates, which fit together like a jigsaw puzzle. These plates sometimes move. The friction causes earthquakes and volcanic eruptions near the edges of the plates. The theory that explains this process is called plate tectonics.

Volcanoes are like giant safety valves that release the pressure that builds up inside the Earth.

A volcano is a geological landform (usually a mountain) where magma (rock of the earth's interior made molten or liquid by high pressure and temperature) erupts through the surface of the planet.

The name "volcano" has its origin from the name of Vulcan, a god of fire in Roman mythology.

As pressure in the molten rock builds up it needs to escape somewhere. So it forces its way up “fissures” which are narrow cracks in the earths crust. Once the magma erupts through the earth’s surface it’s called lava.

Magma is liquid rock inside a volcano.

Lava is liquid rock (magma) that flows out of a volcano. Fresh lava ranges from 1,300° to 2,200° F (700° to 1,200° C) in temperature and glows red hot to white hot as it flows.

An active volcano is one that erupts regularly.

A dormant volcano is one that has not erupted for many years, although there is still some activity deep inside.

An extinct volcano has ceased to be active.

A volcanic eruption is when hot rocks and lava burst from a volcano.

Geysers are springs that throw boiling water high in the air. They are caused by volcanic heat warming trapped ground water.

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

The world's largest, active volcano is Mauna Loa in Hawaii, where famous coffee is grown in the rich volcanic soils.

Mauna Loa is 13,677 feet above sea level. From its base below sea level to its summit, Mauna Loa is taller than Mount Everest. Mauna Loa is about 36 m (120 ft) lower than its neighbour, Mauna Kea.

Hawaii was formed by 5 volcanoes. Mauna Loa, and Kilauea are the only active volcanoes.

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