Volcano Anatomy

purpose. Early earth had a mantle that wasn't very oxidized but was just waiting for oxygen to react with it.

The gases emitted from early volcanoes reacted with oxygen as they were emitted. Hydrogen gas may have been one of these, reacting with oxygen to make water. It was only when the gases were mostly mixed with oxygen from bacteria that real oxygen gas could accumulate. As the mantle itself became oxidized, fewer of these gases were emitted and more gases that were already oxidized were more likely to be emitted from newer volcanoes. It's hard to know much about early volcanoes as the oldest volcano on earth – Mount Etna – is only about 350,000 years old.

VOLCANO ANATOMY

What are the pieces and parts of a volcano? They all look different but have similar parts to their anatomy. This brief glossary covers things you'll see in figure 31 on volcano anatomy:

Figure 31.

The main feature you'll see is the magma chamber beneath it. The magma is molten and hot, sitting up to 10 kilometers below the earth's surface. This is what is emitted out of it as lava. The vent is the top part of the volcanic mountain where most of the magma comes out. This is where you see the main eruption. You can have side vents off the main vent as well.

Magna and lava can be thin or thick. They can also be gaseous or non-gaseous. Lava that can flow downhill will do this as a typical lava flow. Some lava is ejected wildly out of the vent as a volcanic bomb. These are at least 26 inches in diameter, cooling quickly as they fly through the air as extrusive igneous rocks. As lava builds up, it forms a lava dome or circular mountain that is caused by slowly moving thick lava.

An eruption column is the hot ash and gases that are released when there is a volcanic eruption. Inside this hot cloud, the air is electric so that you might see lightning and thunder. This leads to an eruption cloud or a falling cloud of ash that falls like snow after an eruption. Ash is dangerous and can suffocate living things. You might see this up to 12 miles above the volcano itself with ash falling thousands of kilometers away from the eruption. Tephra are pieces of magma that break apart after being ejected from the lava vent. They can be giant boulders or tiny ash pieces; tephra are very dangerous. Acid rain is a common occurrence which happens when sulfur dioxide or nitrogen oxide coming out of the volcanoes mixes with water in the air.

Pyroclastic flows are very deadly. The stuff coming down the mountainside is very hot, gaseous, and fast-moving. Tephra are mixed in with these gases to make this deadly cloud. Lahar is also dangerous. This is a mixture of volcanic gases, ash, and local water to create a giant mudflow that can destroy whole towns. Fumaroles are any holes, fissures, or cracks near volcanoes where heat, gases, or magma come out. Sulfur gases come from these areas, for example. Cracks are also openings that reach down into the magma pool.