Douglas Wiens, of the Washington University in St. Louis, in Antarctica.
Click on image for full size
Image Courtesy of Douglas Wiens, Washington University in St. Louis

Study of Glacial Earthquakes Shakes Up Idea of How Ice Streams Move
News story originally written on June 5, 2008

New research shows that a 7,000-square-mile region of the Whillians Ice Stream in West Antarctica moves more than two feet twice every day in an earthquake-like pattern equal to a Magnitude 7 earthquake. Seismologists use the magnitude scale to describe the seismic energy released by an earthquake. An earthquake that measures between 7.0 and 7.9 on the scale is considered "major," and can cause serious damage over large areas of the world.

In an earthquake, stress builds between two plates on the Earth's crust as the energy of their movement accumulates. Finally, one plate or the other moves, causing shudders and jolts at the Earth's surface.

A similar movement was observed in the Whillians Ice Stream by the research team. Using GPS sensors and seismic sensors, the researchers say they have measured what they are calling a "stick-slip" interaction on the massive ice stream. The "stick-slip" pattern in the ice sheet is very different that the way scientists usually think of ice streams as flowing at a constant speed.

"Glaciologists model the flow of glaciers using the assumption that it's basically a kind of creeping kind of motion. But recently we've been seeing seismic signals coming from a number of ice streams and glaciers, and no one's been able to interpret them," said Douglas Wiens, a professor of Earth and planetary sciences at Washington University in St. Louis, who led the research team.

The "stick-slip" events on the Whillians Ice Stream occur twice a day and seem to be related to the daily tidal action of the Ross Sea. During each slip, a 96 by 193 kilometer (60 by 120 mile) region of the the ice stream moves as much as .67 meters (2.2 feet). The ice is 609 meters (almost 2000 feet) thick. The slip takes place over about 25 minutes, so scientists standing right on the slipping ice stream don't feel anything. In contrast, most rock earthquakes, which can take place in as little as a few seconds, are felt strongly by people in the area.

The new findings don't say if these ice movements have anything to do with global warming. But they are significant, because they add another piece to the mosaic of scientific understanding of ice dynamics.

Last modified July 8, 2008 by Becca Hatheway.

Shop Windows to the Universe Science Store!

Our online store includes fun classroom activities for you and your students. Issues of NESTA's quarterly journal, The Earth Scientist are also full of classroom activities on different topics in Earth and space science!

Windows to the Universe Community

News

Opportunities

You might also be interested in:

Traveling Nitrogen Classroom Activity Kit

Check out our online store - minerals, fossils, books, activities, jewelry, and household items!...more

The Antarctic Region

What Will You Find There? South of the Antarctic Circle (at 66.5°S latitude) you will find the continent of Antarctica surrounded by the Southern Ocean, the geographic South Pole and the magnetic South...more

What Is an Earthquake?

The expression “on solid ground” is often used to describe something as stable. Usually the solid ground underfoot seems very stable. But sometimes it is not. "The ground seemed to twist under us like...more

Plate Tectonics

The main force that shapes our planet’s surface over long amounts of time is the movement of Earth's outer layer by the process of plate tectonics. This picture shows how the rigid outer layer of the...more

Glaciers and Ice Sheets

For a glacier to develop, the amount of snow that falls must be more than the amount of snow that melts each year. This means that glaciers are only found in places where a large amount of snow falls each...more

The Cryosphere

Frozen water is found in many different places on Earth. Snow blankets the ground at mid and high latitudes during winter. Sea ice and icebergs float in the chilly waters of polar oceans. Ice shelves fringe...more

Global Warming: Scientists Say Earth Is Heating Up

Earth’s climate is warming. During the 20th Century Earth’s average temperature rose 0.6° Celsius (1.1°F). Scientists are finding that the change in temperature has been causing other aspects of our planet...more

Triggers of Volcanic Eruptions in Oregon's Mount Hood Investigated

Scientists have learned that Mount Hood, Oregon's tallest mountain, has erupted in the past due to the mixing of two different types of magma. "The data will help give us a better road map to what a future...more

Windows to the Universe, a project of the National Earth Science Teachers Association, is sponsored in part is sponsored in part through grants from federal agencies (NASA and NOAA), and partnerships with affiliated organizations, including the American Geophysical Union, the Howard Hughes Medical Institute, the Earth System Information Partnership, the American Meteorological Society, the National Center for Science Education, and TERC. The American Geophysical Union and the American Geosciences Institute are Windows to the Universe Founding Partners. NESTA welcomes new Institutional Affiliates in support of our ongoing programs, as well as collaborations on new projects. Contact NESTA for more information. NASA ESIP NCSE HHMI AGU AGI AMS NOAA