Sharing the Fascinating Ice Age Floods Story Since 1995
Sharing the Fascinating Ice Age Floods Story Since 1995
View a gallery of diagrams for different volcano types, with glossaries
The three major types of volcanoes—cinder cone, composite, and shield—each exhibit unique, lesser-known subterranean and surface features, including lava bombs, lahars, and spatter. Other types of volcanoes include lava domes, calderas, fissure volcanoes, and Maars and tuff rings.
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.
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.
Lava flow viscosity plays a significant role in the type of volcano formed
Magma usually stays underground because of a balance between its upward pressure, the weight of the Earth’s crust above, and the crust’s rock strength. Landslides can reduce crust weight, while built-up gas pressure can strengthen magmastatic pressure.Thin, runny flows spread quickly before cooling, producing expansive layers that build over time into wide shield volcanoes. The ejection and fast hardening of thicker lava flows and pyroclastic material create steep slopes and the characteristic cone shape of composite volcanoes.
Explosive volcanic eruptions happen when magma pressure overcomes rock strength
The composition of magma affects the explosivity of volcanic eruptions. Silicate-rich magma contains extensive molecular chains that trap dissolved gases like water and carbon dioxide. These gases build pressure until they violently escape, creating explosive eruptions. Low-silica magmas produce gentler eruptions categorized as effusive.
Magma usually stays underground because of a balance between its upward pressure, the weight of the Earth’s crust above, and the crust’s rock strength. Landslides can reduce crust weight, while built-up gas pressure can strengthen magmastatic pressure.