Maggie and the Volcano - Science Stories

Racing down the volcano like a fiery snake, lava roars and hisses and crackles. Dr. Maggie Mangan’s job is to walk across the volcano’s fresh, hot crust—which was molten rock just an hour before—and take samples from the stream of flowing lava.

As she steps close to the lava flow, her face feels hot under her protective mask, as if her skin is beginning to burn.

Walking on an erupting volcano is all in a day’s work for Maggie.

Maggie is a geologist who specializes in the study of volcanoes. Her office is perched on the rim of the world’s most active volcano, Kilauea (key-lah-WAY-ah). That volcano is in Hawaii Volcanoes National Park on the island of Hawaii.

Usually, when a volcano erupts, everyone runs away from it. How can Maggie get so close to Kilauea during an eruption?

“Quiet” Eruptions
The reason is that Kilauea is different from most volcanoes. One important difference is that Kilauea does not explode when it erupts. Instead, its lava flows steadily, forming hot streams and underground tubes full of lava. Maggie explains that the magma in the Hawaiian volcanoes is what makes them different.

The magma in most other volcanoes is thick, like pudding, because it contains a lot of a chemical called silica. When this magma comes to the surface (where it is called lava), it can explode. These explosions are caused by gases—mostly steam—trapped in the magma.

When the magma comes out, a huge amount of gas inside it expands instantly, forming bubbles that can burst with explosive force. The thick lava then piles high, forming a mountain shaped like an anthill.

But inside Kilauea, the magma contains very little silica and very little gas. It’s called basaltic (buh-SAWL-tick) magma.

Because basaltic lava flows more like syrup than pudding, the small amount of gas in it escapes without an explosion. This runny lava creates a wide mountain with a curved top, like a warrior’s shield lying on the ground. Because of this shape, the Hawaiian volcanoes and a few others in various parts of the world are called shield volcanoes.

Why do shield volcanoes have a different kind of magma? Scientists think the reason is that shield volcanoes do not form on the cracks, or faults, in the Earth’s crust as explosive volcanoes do.

Instead, they form over hot spots in the Earth’s mantle. These mysterious places deep in the Earth melt holes in the crust, allowing basaltic magma to rise to the surface. For this reason, shield volcanoes are also called hot-spot volcanoes.

Walk Softly
To study lava flows, Maggie walks on hardened lava that may be barely two inches thick. “I walk lightly and go fast,” she says.

A few years ago, a scientist working near her broke through the crust over a fiery pool of lava. “He’s fine now,” says Maggie. “But working near fresh lava is the most dangerous part of our job.”

Sometimes lava is easy to reach because it oozes over the ground in what are called breakouts. But at other times the lava flows through underground tubes. To get to this lava, Maggie must find a skylight, which is a hole in the hardened lava that lets her see down into the underground tubes. “When you reach one, you feel like you’ve been hit by a board, the heat is so intense,” she says.

Using a radar gun and other measuring devices, she can tell how much lava is in a lava tube and how fast it’s flowing. When the lava slows down, the eruption might be coming to an end.

To collect a sample, Maggie throws a hammerhead attached to a stainless steel cable into the river of molten rock.

Then she pulls out her catch—lava that clings to the hammerhead like taffy. It hardens quickly as it cools, turning into a black, glassy rock.

These lava samples contain crystals and other minerals that Maggie studies for clues about the lava’s history. She can tell how long the molten rock sat in the magma chamber (which is a kind of holding tank inside the volcano) before it was erupted and how hot it was at the time of the eruption.

Clues to the End
From the beginning of an eruption to its end, the lava’s temperature and the mixture of minerals in it change. By measuring the temperature and studying the composition of the lava, scientists hope to learn how to predict the time when almost any shield volcano will stop erupting. The photograph to the right shows the two kinds of rock formed by shield volcanoes.

Foreground: Extremely fluid lava hardens into sheets of puffy, sometimes ropy, rock called pahoehoe (pah-hoy-hoy).

Background: Thicker lava forms a higher pile of crumbly, razor-sharp rocks called aa (ah-ah). Geologists have borrowed these Hawaiian words to identify these rock forms.

Maggie and her helpers are not the only people who love Kilauea. Millions of people visit Hawaii Volcanoes National Park each year to see the beauty of Kilauea’s gentle eruptions.

If you have a chance to visit the park, you might spot some people near a hot lava flow. They’re scientists who think it’s cool to be hot.