geology

Wednesday 11 May 2011

What is a volcano


What is a volcano?
volcanic rocks 



A volcano is a vent or 'chimney' that connects molten rock (magma) to the Earth's surface. It includes the surrounding cone of built-up material. Magma erupting from a volcano is called lava. Gases and pieces of rock erupt from volcanoes too.
A volcano is active if it erupts lava, releases gas or shows seismic activity. It is dormant if it hasn't erupted for a long time but could again one day. An extinct volcano will never erupt again.
The explosiveness of a volcanic eruption depends on how easily magma can flow and the amount of gas trapped in it. Large amounts of water and carbon dioxide are dissolved in magma. They behave like gas in fizzy drinks. After opening the bottle the gas expands, forming bubbles that escape. This also happens when magma rises quickly through the crust - gas bubbles form and expand up to 1000 times their original size.
How do volcanoes effect the weather?
The first is how the weather near an erupting volcano is being affected. The second is how large eruptions will affect the weather/climate around the world. I think more people are worried about the second issue than the first. As far as we know, the main effect on weather right near a volcano is that there is often a lot of rain, lightning, and thunder during an eruption. This is because all the ash particles that are thrown up into the atmosphere are good at attracting/collecting water droplets. Another problem in Hawaii is that involves the formation of volcanic fog. The ongoing eruption is very quiet, with lava flowing through lava tubes and then into the ocean.
How do volcanoes effect people?
Volcanoes affect people in many ways, some are good and some are not. Some of the bad ways are that houses, buildings, roads and fields can get covered with ash. As long as you can get the ash off (especially if it is wet), your house may not collapse, but often people leave because of the ash and are not around to continually clean off their roofs. If the ash fall is really heavy it can make it impossible to breathe.

The good part of volcanoes
The main good effect that volcanoes have on the environment is to provide nutrients to the surrounding soil. Volcanic ash often contains minerals that are beneficial to plants, and if it is very fine ash it is able to break down quickly and get mixed into the soil.

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