Volcanoes 101 | National Geographic
Our planet has a violent soul, majestic and often destructive. Volcanic explosions rattle our collective imagination: Krakatoa, Mount St. Helens, Etna. Yet, lay your eyes on the images; they simultaneously strike fear and awe in our hearts.
But how did these giant mountains form, and where does all that destructive force come from? At least 50 eruptions rock the earth each year, meaning our planet is literally bursting apart at the seams. The Earth's crust is made up of about 17 slabs of land called tectonic plates that float on the superheated magma that makes up most of the planet's interior.
Magma is the Earth's lifeblood, churning restlessly beneath the crust, and wherever it can, it’s trying to burst through. It’s at these spots that volcanoes form. Our planet is home to some 500 active volcanoes. While some volcanoes, like those in Hawaii, break through a thin point in the crust called a hotspot, the vast majority of volcanoes occur on active fault lines where tectonic plates meet.
The most volatile region is the Ring of Fire, a geological fault belt that rims the Pacific Ocean and holds roughly 75 percent of all the Earth's volcanoes. Typically, volcanoes take one of two forms: shield volcanoes, which are wide and broad with lava usually slowly oozing out of them, and composite or stratovolcanoes, which are steeper and more violent.
When hot liquid magma reaches the surface, whether in a slithering flow or a booming eruption, we call it lava. Though molten lava may seem threatening, it's not known to move quickly. A volcano's pyroclastic flow is far more deadly; this poisonous ash cloud can race down the slope of a volcano like a bullet train, obliterating everything in its path at speeds topping 100 miles per hour. It’s what stopped the residents of Pompeii dead in their tracks.
But despite the volcano's brutal destruction, it is also a force of beauty and rebirth for the planet. Lava creates new lands where life can flourish. Like it or not, volcanoes are part of the planet's life cycle. As the Earth continues to explode, gurgle, and slither its molten heart out, we must learn to live side by side with its awesome power.