Picturing Volcanoes

When you picture a volcano, what do you imagine? You probably think of a tall, pointed mountain. Perhaps you imagine red-hot lava spewing from the top or gushing down the sides. Dark towers of ash and smoke might jet into the sky.

All of these things can happen, but this image is only one type of eruption from one type of volcano. There are many different kinds of volcanoes and eruptions that happen all over the earth. Shield volcanoes, stratovolcanoes, and cinder cone volcanoes are three of the main types.

Shield Volcanoes

Shield volcanoes sometimes don’t look like volcanoes at all, but these are the largest volcanoes on the planet! Instead of a pointed peak, these volcanoes are wide with gentle, sloping sides. They get their name from a warrior’s shield; people thought these volcanoes were shaped like a shield laying on the ground.

The Hawaiian volcanoes of Mauna Loa and Kīlauea are both active shield volcanoes. This means that both of these volcanoes are still erupting. Mauna Loa is the largest active volcano on Earth. It reaches all the way to the bottom of the ocean. Less than half of its height is above the water. If Mauna Loa and Mount Everest were placed side-by-side, Mauna Loa would be taller!

Eruptions on Mauna Loa and Kīlauea are slower than you might think. Lava on these volcanoes can flow up to 35 miles per hour. That’s fast for a car driving around your neighborhood, but it’s slow for a volcanic eruption. What shield volcanoes lack in speed, they make up for with their long lives. Shield volcanoes can erupt for millions of years.

Stratovolcanoes

Stratovolcanoes come closest to the cartoon image of a volcano. These volcanoes are tall and may have pointed, snow-covered summits. They have steep sides. When these volcanoes erupt, they tend to put on a dramatic show.

Mount St. Helens is a famous stratovolcano in Washington State. It erupted on May 18, 1980. Hot ash, steam, dirt, rocks, and gasses rushed down the side and out of the top of the volcano at hundreds of miles per hour. Mudflows, called lahars, flooded the river valleys around the volcano. The eruption was so violent and blew away so much dirt and rock that Mount St. Helens went from being the 5th tallest mountain in the state to the 92nd. Fifty-six people died in the eruption.

There are many other stratovolcanoes beside Mount St. Helens. Mount Rainier in Washington State is also an active stratovolcano. Mount Vesuvius, which buried the ancient city of Pompeii in 79 CE is a stratovolcano, and so is Krakatoa in Indonesia which had a devastating eruption in 1883.

Cinder Cone Volcanoes

Cinder cone volcanoes are the most common type of volcano on Earth. They’re also the smallest kind of volcano. Most are only a few dozen or a few hundred feet tall. Like stratovolcanoes, cinder cone volcanoes have the shape you might think of when picturing a volcano: steep sides and a summit with a crater at the top.

When a cinder cone volcano erupts, hot gasses shoot out and mix with lava as they rise. Pieces of lava are thrown into the air. These pieces of lava cool as they fall back to earth. They land on the ground as solid rock. These rocks are called cinders. Cinder cone volcanoes are piles of these small pieces of rock.

Sunset Crater near Flagstaff, Arizona is one of the most famous cinder cone volcanoes in the United States. You can hike part of the way up this 1,000-foot-tall volcano. You should always be careful when exploring volcanoes, but Sunset Crater isn’t active. It formed about 1,000 years ago and hasn’t erupted since.

Shield volcanoes, stratovolcanoes, and cinder cone volcanoes all bring magma, hot fluid from inside the earth, to the surface as lava which hardens into rock. Big or small, volcanoes help shape our planet. Even if they look different than what you might think of as volcanoes, each type is important.