In a new study, Northeastern earth and environmental sciences professor Jennifer Cole has discussed what causes earthquakes and how one natural disaster can lead to another.

As to what causes earthquakes, Cole says that they result from the movement of tectonic plates.

As tectonic plates slide past each other, energy builds up in the rocks until they can no longer hold the stress.

This causes failure in the form of breaking rocks, sending energy waves outward.

The earthquakes in Haiti, China, Japan, and Chile all happened because of this series of events.

Glaciers may also cause earthquakes.

During the last glacial period, the ice sheet was up to 2.5 miles thick. This pushed down on the Earth’s crust, causing a depression.

When the weight was lifted due to glacial melting, the depressed crust began to stick-slip on its way back to the pre-depressed elevation.

In addition, humans can cause earthquakes by damming rivers, creating a reservoir heavy enough to cause a depression in the earth’s crust.

A massive earthquake is usually followed by a sequence of aftershocks, landslides and tsunamis.

Earthquakes are capable of causing tsunamis.

In the unique case when an earthquake occurs on the ocean floor, a rock is forced up, causing a disturbance in the water column that extends to the ocean surface.

Waves then travel outward in a series of concentric circles at a rapid rate, up to 550 miles per hour, or as fast as a jet airplane travels.

When tsunamis reach shallow water, they slow down and grow taller, forming massive waves.

These waves travel inland and cause flooding and increase the potential of coastal landslides.

Some scientists are making the case that global warming is contributing to an increase in earthquake activity by making the ocean water warmer, and therefore, heavier.

Additionally, melting glaciers take weight off of tectonic plates, which can cause them to pop upwards in those areas, resulting in earthquakes.

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A killer surge of sea water racing across an ocean should, theoretically, generate an electrical current that ought to be detectable by existing undersea cables, say researchers.

The idea has been successfully modeled using what’s known about the 2004 Indian Ocean Tsunami. It looks like the wave moving through the Earth’s magnetic field probably generated a small electrical current. That, in turn, could be absorbed by undersea cables and ought to be noticed as a telltale power surge.

If so, then undersea cables could be a quick way to detect and monitor dangerous tsunamis in the open ocean.

“This should be seen as a technical demonstration paper,” said Manoj Nair of the University of Colorado, referring to his paper in the February issue of the journal Earth, Planets and Space. “We have a long way to go.”

According to Nair and his co-authors’ model, the 2004 Indian Ocean Tsunami surging along, and interacting with the Earth’s magnetic field as it went, should have induced a 500-millivolt (or half of one volt) electrical current in undersea cables.

Just how the electricity is generated harkens back to the 19th century scientist Michael Faraday, who showed that water flowing through a magnetic field can induce a flow of electrons — a.k.a. an electrical current. Ocean water is particularly good at this because it is very salty, making it a better conductor of electricity as it flows through the Earth’s magnetic field, Nair explained.

As for the cables that could absorb some of that electrical flow, they are the sorts used for telecommunications across oceans. Today’s modern fiber optic cables would not, of course, carry the current, Nair said, but they could just if a bit of copper wire were added to them.

“We also have a network of of old copper cables all over the oceans that are no longer in use,” he said. These could, theoretically become part of an array that is used to detect tsunamis.

Of course, even if a cable-based tsunami detection idea is proven in the real world, it will only be at best a small part of a larger system of buoys and other monitoring systems to keep people informed about tsunamis, Nair said.

In fact, there could be some drawbacks to even attempting to set up such a detection system, according to geophysicist Mark Everett of Texas A&M University.

“From a practical way of monitoring tsunamis, it has problems,” Everett said. For instance, there may not be cables in the right places and there are big costs that go with laying more cables, as well as maintaining existing cables. There is also a big risk of false alarms and other difficulties, he said.

On the other hand, said Everett, what Nair and his colleagues have modeled could have other uses — such as for studying other sorts of flows, currents, tidal surges and even internal waves in the oceans.

“There are many other different sorts of flow that scientists would like to study,” Everett told Discovery News. “That could lead to other applications in the future.”

The moon may have been adopted by our planet instead of descended from it.

If a new twist on a decades-old theory is right, conditions in the early solar system suggest the moon formed inside Mercury’s orbit and migrated out until it was roped into orbit around Earth.

The idea flies in the face of scientific consensus, known as the giant impact hypothesis, which holds that the moon formed from red-hot debris left over after a Mars-sized object collided with Earth around 4.5 billion years ago.

However, the moon has several curious traits that go unexplained with that theory, and Robert Malcuit of Denison University has argued for decades for an alternative view of our moon’s history.

Malcuit’s version of events is tantamount to cosmic blasphemy, but scientists have recently found 4 billion-year-old minerals in Australia that suggest our planet was too cool to have sustained a cataclysmic moon-forming impact early in its history.

“Everything in the giant impact model is hot, hot, hot,” he said. “It’s incompatible with what we see in the geologic record. Earth is cool enough at that time to have ocean water on its surface.”

Malcuit’s computer modeling studies, which he has worked on since the 1980s, show that it is possible for Earth’s gravitational pull to capture the moon.

At first, the moon’s orbits would have been highly elliptical, swinging close to Earth and then far away about eight times a year.

The gravitational pull from each pass would have stretched the planet 18 to 20 kilometers (11.2 to 12.4 miles) near the equator, churning the hot mantle and crust. Rocks closer to the poles, like those found today in Australia, would have been spared. The upper layers of the newly-captured moon would have melted from gravitational friction, until the satellite’s orbit stabilized about 3 billion years ago.

Malcuit presented his theory at the annual meeting of the Geological Society of America in Portland, Ore.

Traditionally, scientists cite the moon’s low density and a lack of iron as reasons why it came from Earth — the giant impact skimmed light material off Earth’s upper layers and flung it into orbit.

“I think this it is highly unlikely,” that Malcuit’s idea is correct, Jack Lissauer of the National Aeronautics and Space Administration in Moffett Field, Calif., said. “Capture is very, very difficult. You have to have just the right velocity and very special parameters to all be just right.”

Lissauer allowed that the current giant impact theory of the moon’s formation may yet be revised, even replaced, but probably not by Malcuit’s capture model. The fact that Earth was cool 4 billion years ago doesn’t mean the moon was captured.

“Heat from the impact dissipated very quickly,” he said. “It wouldn’t take 100 million years, and it certainly wouldn’t take 500 million. The impact is not going to affect Earth at 4 billion years ago.”