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Thursday, October 2, 2014

Is It Magma or Lava??

When geologists group volcanoes, it’s usually into four main kinds.

The Hawaiian islands are made up of Shield Volcanoes. A shield volcano is a broad, domed volcano with gently sloping sides that is built up by successive outpourings of very fluid lava.

Last week I posted about the Kilauea eruption on the Big Island. I thought this week you might like to learn a little about volcanoes.

You may hear a variety of terms used when people talk about volcanoes. What’s the difference between the terms? Here are a few definitions that may help you.

Caldera—The large basin-shaped depression formed when the roof of the magma chamber collapses because massive amounts of magma have erupted. Some are formed when a huge explosion removes the upper part of the volcano.

Crater—A depression around the orifice of a volcano.

Magma—Molten rock within the earth’s crust that is capable of extrusion onto the surface.

Lava—Molten rock that has extruded onto the surface.

Lava Tube—A tunnel formed under a lava flow.

Pahoehoe—As the lava flows along the tube, a top crust will form. As the lava flows underneath, the top begins to wrinkle. This is pahoehoe.

Aa—Sometimes the pahoehoe will shift as it cools and loses gas, forming sharp edges and spiny projections.

If you would like to see some photos of Pahoehoe and Aa flows, or would like to read more about the Hawaiian volcanoes, here is a site to visit.

Aloha, and Mahalo for visiting!

The Hawaiian Island Detective Club
Book One—Pineapples in Peril
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Book Two—Menehunes Missing
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I love hearing from my readers! Mahalo for visiting and commenting. Aloha! --Cheryl