Dr. Universe explains how volcanoes erupt

Ask Dr. Universe is a science-education column from Washington State University.

  • Thursday, February 7, 2019 1:51pm
  • Life
Illustrations by Rob McClurkan

Illustrations by Rob McClurkan

Dr. Universe: How do volcanoes erupt? –Miles, 10, Tampa, FL

Dear Miles,

Wherever we find a volcano on the surface of our planet, we can find the source of an eruption beneath it. That’s what I found out from my friend John Wolff, a volcanologist at Washington State University.

Our planet is home to all kinds of volcanoes that erupt in different ways. Some eruptions are quiet and continuous, with a slow flow of lava. Other volcanoes erupt explosively and can spew ash and lava hundreds of feet up into the sky. All of this lava has its start underground in the form of something called magma.

Wolff said that scientists used to think there were large pools of hot liquid beneath volcanoes. Now we know it isn’t quite that simple. Magma is not really a liquid, but rather a kind of sludge or slurry. It helps to think of it kind of like honey.

“If you put honey in the cupboard for a long time it will solidify,” Wolff said. “But if you set it in a pan of hot water, you can return that honey to a more liquid state.”

Wolff is very curious about volcanoes and told me about super volcanoes like the Yellowstone Caldera in Wyoming. The pools of magma under the Yellowstone super volcano are anywhere from three to 12 miles deep.

When a volcanic eruption is about to happen, magma near the surface of the earth gets heated up by even hotter magma from below. The hot magma deep in the earth starts to melt the crystals in that magma above and the magma becomes more liquid-like. When this happens, the system is in a dangerous state, said Wolff. The volcano could erupt at any time.

The eruption also has something to do with density. When we talk about density we are talking about how tightly packed together the particles are in an object. For example, if you put an object in water and that object floats, the object is less dense than the water.

Magma from the earth is actually lighter, or less dense, than the rock around it. As the magma starts to rise, bubbles of gas start to form inside the magma and they can’t escape. That also makes the pressure build up in the volcano, makes the magma rise even more, and eventually erupt.

In fact this pressure is one of the things that is a major difference between volcanoes on land and volcanos under the sea. Yep, there are also submarine volcanoes deep in the ocean. In fact, about 75 to 80 percent of volcanic eruptions on our planet occur underwater.

Water pressure can prevent those gassy bubbles from forming in lava, so the explosions under the sea aren’t quite as huge as eruptions on land. Because it is so dark on the ocean floor, it’s harder to see these eruptions. But whether at land or at sea, there’s likely some volcanic activity happening somewhere on our planet at this very moment.

Sincerely,

Dr. Universe

More in Life

Thom Cantrell, one of the organizers of the upcoming International Conference for Primal People, holds up a mould of a Sasquatch footprint. He said the mould was taken in the Blue Mountains in Oregon by Paul Freeman, a well-known Sasquatch hunter who’s 1994 footage of a Sasquatch in that area made big waves in the believer and skeptic communities alike. Photo by Ray Miller-Still
All things Sasquatch in Enumclaw

Washington state is famous for countless reasons. It’s the birthplace of Starbucks… Continue reading

RHS Students gear up for Bubblin Brown Sugar dance competition

The competition is April 27 at Garfield High School.

How to be a backyard micro farmer

Do you have a small space? Perhaps just a balcony or patio… Continue reading

Special police partners honored

King County Sheriff’s Office dedicates new memorial to honor K9 service dogs and handlers.

Renton Schools Foundation hosts annual breakfast fundraising event

The Renton Schools Foundation (RSF) is hosting its 10th Annual Fundraising Breakfast… Continue reading

Photo by Haley Ausbun.
Rooftop dragon roars over Renton

New 25-foot iconic sculpture draws crowd downtown.

Renton Rotary selects Teachers of the Month for April

Silvia Flores, John Hoag and Kristen Murphy were selected as teachers of the month.

STREAM offers after school curriculum for Highland kids

A new program is redefining the North Highlands Neighborhood Center

Photo of Renton native Matt House by Mass Communications Specialist 2nd Class Brad Gee
Renton native propels submarine legacy into the future

By M. Dawn Scott Navy Office of Community Outreach As citizens of… Continue reading

Most Read