Even if you don’t live near a volcano, you’ve been impacted by their activity.
It’s estimated that more than 80% of our planet’s surface has been shaped by volcanic activity. They’ve helped create our mountain ranges, plains, and plateaus, and have even helped fertilize the land that we now use to grow crops.
These critical mounds come in many shapes and sizes. This graphic by Giulia De Amicis provides a brief introduction to volcanoes, explaining their different types of shapes and eruptions.
Types of Eruptions
A volcano starts to form when molten rock rises from a crack in the Earth’s surface, which often emerge along tectonic plate boundaries.
Magma rises to the Earth’s surface because it’s lighter than rock. When it surfaces or erupts, it’s referred to as lava.
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There are various types of volcanic eruptions, depending on the lava’s temperature, thickness, and composition. Generally speaking, high gas content and high viscosity lead to explosive eruptions, while low viscosity and gas content lead to an effusive, or steadily flowing, eruption.
The Four Main Types of Volcanoes
Volcanoes vary in size and structure, depending on how they’re formed. Most volcanoes types fall into four main groups:
Shield Volcanoes
Shield volcanoes are built slowly, from low-viscosity lava that spreads far and quick. The lava eventually dries to form a thin, wide sheet, and after repeated eruptions, a mount starts to form.
From the top, these types of volcanoes look like a shield, hence the name. While these volcanoes take a while to form, they aren’t necessarily low. In fact, the world’s tallest active volcano, Mauna Kea in Hawaii, is a shield volcano.
Stratovolcanoes
Also known as composite volcanoes, stratovolcanoes are built relatively fast, at least compared to shield volcanoes. This is because, in between lava eruptions, composite volcanoes emit ash and rock, which helps add structure to the mound rather quickly.
Some well-known composite volcanoes are Mount Fuji in Japan, Mount St. Helens in Washington, and Mount Cotopaxi in Ecuador.
Volcanic Domes
Opposite to shield volcanoes, volcanic domes are formed when lava is highly-viscous. Because the thick lava can’t travel very far, it starts to pool around the volcano’s vent.
This can sometimes create a pressure build-up, meaning dome volcanoes are prone to explosive eruptions.
Cinder Cones
These types of volcanoes typically don’t release lava. Rather, their eruptions typically emit volcanic ash and rocks, known as pyroclastic products.
Cinder cones are characterized by a bowl-shaped crater at the top, and usually don’t exceed 400 m (1,312 ft) in height.
How Volcanoes Benefit the Earth
Volcanoes have a number of ecological benefits. Once broken down, volcanic materials create exceptionally fertile soil, which can help build prospering new habitats for animals and plants.
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Volcanic eruptions can also help cool our climate. When a volcano explodes, ash and sulfur gas from the eruption combine with water droplets and get trapped in the atmosphere for years. This has a cooling effect which is extremely beneficial to us, especially given our current global warming situation.
Dr. Tracy Gregg, associate professor for the University at Buffalo’s geology department, told Accuweather that “volcanoes have actually helped to keep the world about 2 to 3 degrees cooler than it otherwise may be.”
