Volcanoes

What are Volcanoes? A volcano is a rupture of the Earth’s crust that allows hot lava, poisonous gases and ash to escape from magma chambers. Volcanoes occur because the Earth’s crust is separated into 17 rigid tectonic plates that float around on the softer mantle. Volcanoes are generally found around places where the plates converge (move together) or diverge (move apart). 20% of all volcanoes are under water.

What causes volcanoes Volcanic activity frequently occurs on the boundaries of tectonic plates. They occur as the pressure within causes the magma below to rise up and explode or escape. The Ring of Fire is a string of volcanoes that run around the edge of the Pacific ocean.

Types of Volcanoes There are four types of Volcanoes:

Fissure Volcanoes Fissure volcanoes are cracks in the ground that are only a few meters wide, but they can be several kilometers in length. Fissure volcanoes are not usually explosive. Lava seeps out of the gaps in the crust’s surface.

Cinder Cone Volcanoes Cinder cone volcanoes occur when large globs of lava are launched from a single event. Most have a bowl-shaped crater in the center.

Composite Volcanoes Composite volcanoes are some of the grandest. They are typically large, steep and symmetrical. They have a crater at the summit which contains a central vent or a clustered group of vents.

Shield Volcanoes Shield volcanoes are almost entirely made up out of fluid lava flows. Vent after vent flows out through the volcano from the center vent. This builds a broad, gentle-sloping cone of a flat, dome shape, similar to a warrior’s shield.

Measuring Volcanic Eruptions Volcanic eruptions are measured using the volcanic Explosivity Index. Each eruption is given a rating of 0-8 with 0 being non-explosive and harmess, and 8 being “Run for your lives, the Earth is melting!” Volcanic eruptions are measured by: Volume of material ejected, Height of the eruptive column Duration, etc