Understanding Volcanoes

Volcanic activity is a fascinating, frightening, and an absolutely essential feature of our planet. Volcanoes are scattered everywhere, from a desert in Africa to the frigid climes of Antarctica, islands in the Pacific, and on all continents. Every day one erupts somewhere. Earth’s volcanoes are familiar to most of us, such as the very active Mount Agung in Bali, Bárðarbunga in Iceland, Kilauea in Hawai’i, and Colima in Mexico. 

However, there are volcanoes spread on worlds across the solar system. Take Jupiter’s moon Io, for example. It’s highly volcanic and spews sulfurous lava from beneath its surface. It’s estimated that this little world nearly turns itself inside out over millions of years due to its volcanic activity bringing material form the interior to the surface and beyond. 

Farther out, Saturn’s moon Enceladus also has geyser features related to volcanism. Instead of erupting with molten rock as on Earth and Io, it spews out slushy ice crystals. Planetary scientists suspect that there is a lot more of this “ice volcano” activity (known as cryovolcanism) spread throughout the distant reaches of the solar system. Much closer to Earth, Venus is known to be volcanically active, and there’s solid evidence of past volcanic activity on Mars. Even Mercury shows the traces of volcanic eruptions very early in its history.

Volcanoes do major work in building up continents and islands, fashioning deep-ocean mountains, and craters. They also resurface landscapes on Earth as they spew out lava and other materials. Earth began its life as a volcanic world, covered with a molten ocean.

Not all volcanoes that have flowed since the beginning of time are currently active. Some are long-dead and will never again be active. Others are dormant (meaning they could erupt again in the future). This is true on Mars, particularly, where a few volcanoes exist among the evidence of their active past.

Most people are familiar with volcanic explosions like the one that blew apart Mt. St. Helens in Washington State in 1980. That was a dramatic eruption that blew part of the mountain away and showered billions of tons of ash on surrounding states. However, it’s not the only one in that region. Mt. Hood and Mt. Rainier are also considered active, although not as much as their sister caldera. Those mountains are known as “back-arc” volcanoes and their activity is caused by plate motions deep underground.

The Hawaiian island chain stems from a hot spot, a weak point in Earth’s crust under the Pacific Ocean. The islands were built up over millions of years as the crust moved over the hotspot and lava vented out to the seafloor. Eventually, each island’s surface broke the water’s surface and kept growing.

The most active Hawaiian volcanoes are on the Big Island. One of them — Kilauea — continues to pump out thick lava flows that have resurfaced much of the south area of the island. Recent eruptions from a vent on the side of that mountain have destroyed villages and homes on the Big Island.

Volcanoes also erupt all along the Pacific Ocean basin, from Japan south to New Zealand. The most volcanic areas in the basin are along plate boundaries, and that whole region is called the “Ring of Fire”.

In Europe, Mt. Etna in Sicily is quite active, as is Vesuvius (the volcano that buried Pompeii and Herculaneum in 79 AD). These mountains continue to affect surrounding regions with earthquakes and occasional flows.

Not every volcano builds up a mountain. Some vent volcanoes send pillows of lava out, particularly from undersea eruptions. Vent volcanoes are active on the planet Venus, where they pave the surface over with thick, viscous lava. On Earth, volcanoes erupt in various ways. 

ThoughtCo