Volcanic eruptions consist of red-hot lava, flowing out of the ground at temperatures as high as 3,600°F (2,000°C). It can create different scenarios, impressive shows of nature. For example, when Kilauea Volcano in Hawaii erupts, it flows into the sea, causing the water to boil and evaporate into huge clouds of steam. Other volcanoes, such as Washington 's Mount St. Helens, causes the mountain to blow its top, sending boulders flying for miles and raining hot rock from the sky.
Lava consists of molten rock from beneath the Earth 's crust. Inside the planet it 's called magma, a mixture of liquids, gases and solids. The crust of the Earth ranges from about 5 to 10 miles thick, and includes all the land and the oceans. Beneath it it 's the mantle, which is made mostly of very hot, solid rock that somehow gets fluid, like modeling clay. The mantle is about 2,000 miles thick, surrounding the iron-nickel core of the planet. Because the pressure at the to of the mountain is not that high, the rock becomes liquefied in a 60 miles thick layer. The tectonic plates of the crust float on this layer, known as the astenosphere.
Still, even if the pressure is lower than that on the layers beneath it, the magma of the astenosphere is still pressurized compared to the surface above it. When there's an opening in the crust, magma can squirt out to the surface. Generally this occurs at the boundaries between tectonic plates, but sometimes there can be an opening in the middle of a plate. Through such an opening magma was able to flow into the center of the Pacific Ocean, building the Hawaiian Islands.
However, most active volcanos occur at the boundaries between tectonic plates. The Pacific Ring of Fire consists of a string of volcanic mountains extending along the western coasts of the Americas, the Aleutian Island chain, and along the eastern coast of Asia, including all of Japan and the Philippines, Indonesia, and many of the islands of Oceania. More than half of the volcanos above the sea level are part of the Pacific Ring of Fire.
There are different types of volcanic eruptions, depending on the composition of the magma, especially the amount of gas dissolved in the molten rock. Magma with few gas bubbles allows lava to flow gently to the surface, and can be safely approached, but magma that is full of gas bubbles can spew hot lava as high as high as 2,000 feet in the air. Such eruptions can cause great devastations even hundreds of miles away, and the greatest eruptions can send so much material into the sky that it shades the surface from sunlight. Cases like this can disrupt weather patterns around the world for years.
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