What’s behind the sudden surge in earthquakes in the middle of the United States?
Image Credit: NASA/JPL-Université Paris Diderot - Institut de Physique du Globe de Paris
Until geologists figure out a way to take a journey to the center of the earth, they’ll have to do their best by using alternative ways to study the earth’s interior. In this Science Update, you’ll hear about a lab designed to do just that by simulating what happens to rocks deep underground.
Some very high pressure research. I'm Bob Hirshon and this is Science Update.
Most of the 2000-ton presses made by Sumitomo Heavy Industries end up on factory floors, stamping out sheet metal. But one of the twelve-foot tall machines has found its way to a concrete bunker at the Center for High Pressure Research at Stony Brook. Here, the machine is helping researchers like Michael Vaughan figure out what happens 700 kilometers beneath the surface of the earth.
A lot of deep earthquakes occur at those depths. And we want to understand what causes them. And understanding the material properties of the rocks that are down there is the key to understanding that.
Since traveling or even drilling that far down is out of the question, Vaughan and his colleagues take minerals and squeeze them in the big press. An anvil made of tungsten carbide concentrates the force onto a point slightly larger than the head of a pin.
The main scientific goal of what goes on in this building, in this laboratory, is to understand the composition of the interior of the earth.
Analyzing the squeezed minerals helps the researchers understand the high pressure world of the earth’s mantle, without having to go there. For the American Association for the Advancement of Science, I'm Bob Hirshon.
Making Sense of the Research
Many of the most intriguing destinations in the scientific world -- the center of the Earth, the surface of Mars, or the bottom of the sea, for example – are expensive, difficult, or even impossible to get to. That’s why scientists come up with models to simulate conditions in these inaccessible places.
At the depths that Vaughan and his colleagues would like to simulate, the pressure can get up to 300,000 atmospheres. That’s 300,000 times the pressure on the surface of the earth. That kind of pressure can crush a diamond if it’s not applied slowly and carefully, and distributed to other materials besides the one that’s being studied. So a lot of space in the press is taken up by extra material that helps moderate the stress on the object in question. (This is closer to what happens in the earth, where minerals are surrounded by miles of other material, and pressures are applied steadily over millions of years.)
The goal of the research is to see what happens to different minerals under the tremendous forces inside the earth. One process that’s of particular interest is called phase transition. That’s when a mineral changes from one form to another, like carbon into diamond. Some scientists believe these phase transitions can help trigger “deep earthquakes” that occur far down in the mantle, but can have devastating effects on the surface.
Now try and answer these questions:
- Why is the high pressure lab necessary?
- Why must the pressure be applied slowly and carefully?
- Why do you think phase transitions might be involved in earthquakes? Click here for the answer.
- What else might scientists learn from using the high pressure chamber?
PBS Online’s Savage Earth shows how the processes beneath the earth cause earthquakes, volcanoes, and other violent natural occurrences.
The USGS site includes the latest United States and global earthquake activity and highlights research efforts to understand earthquakes and reduce their hazards.
The Tech Museum has this companion site to their exhibit on Earthquakes.