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Glowing avalanche
Glowing avalanche
A mixture of hot gas and rock that travels at great speed down the side of a volcano, just like an avalanche. It is also known as a pyroclastic flow. It is one of the most destructive results of an eruption.
Volcanoes sometimes explode sideways, sending gas, ash, and other forms of tephra hurtling down the side of the volcano instead of up into the air. This fiery mixture moves with great speed and behaves like a snow avalanche, but moving even faster and with even greater destructive
Magma begins to find a new route to the surface.
power. It reaches temperatures approaching 1,000°C.
The explosive eruptions that cause glowing avalanches occur when acid magma that is full of gases builds up enough pressure to blow the top of the volcano apart. The pressure that builds up before this happens can be enormous
and can cause any weak rock above the magma chamber to fracture. This is why just before explosive eruptions there are often many small earthquakes. Each earthquake marks the snapping
of rocks close to the volcano or in the cone.
When a route to the surface is found, the volcano erupts like a shaken soft-drink bottle when the cap is taken off.
Sometimes the rocks in the side of the volcano are weaker than the plug of lava sealing the main vent. When this is the case, the new magma can burst through the side of the volcanic cone, and the full force of the eruption is sent out sideways, rather than upward. It is like firing an enormous gun at the surrounding landscape.
First, a chunk of the cone is blown away. Then the gases, ash, and rock are mixed together and thrown sideways with tremendous force. Everything standing above the ground—trees, houses, and so on—is blown away, and the land is left bare for tens of kilometers from the volcano.
One of the most devastating eruptions in historic times that included a glowing avalanche happened in 1902 on the Caribbean island of Martinique. The volcano
 Glowing avalanche—The Mount Pelée eruption on Martinique. This picture shows the devastation in the immediate aftermath.
 Glowing avalanche —The formation of a glowing avalanche.
Vent plugged by old lava
Magma chamber
Gases and ash blow out of the side of the volcano.
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