Landslides and Mariana

Science 2013-03-27

With all the excitement happening on Mars, interesting discoveries on our planet are sometimes off our radar. However, scientists have recently been looking at somewhat isolated parts of the Earth. This has included landslides or rock avalanches in the four corners of the world and also Mariana Trench, an 11-kilometres deep sea trench.

With all the recent rain, the risk of landslides has increased in some places. Landslides or rock avalanches emit energy when they occur. What if this energy could be detected in a similar way to the energy emitted by earthquakes?

Well, recently, research has been published detailing a method that could enable a landslide’s trajectory to be reconstructed in 3D. By examining numerous landslidesall over the world using their technology, researchers could better understand the characteristics leading to a landslide. Eroded cliffs that can no longer support the weight upon them are susceptible to collapsing. The following rock fall can destroy all that is in its path for several kilometres. In remote areas, however, this could goundetected save for the local communities. Detecting the energy emitted could enable rescue services to be alerted immediately irrespective of the remoteness of the landslide.

The individual waves given off by landslides are longer than those for earthquakes. More than one wave occurs for landslides as opposed to a brief, violent energy emission for earthquakes.

However, this system has its limitations. At the present time, the technology alone can only determine a landslide of at least 4.5 magnitude and to within a 100km of its point of origin. These data need to be amalgamated with satellite images and local reports to be able to get an accurate location for a landslide. The technology does, however with satellites, enable the calculation of the direction and mass of moved rocks and debris.

It is hoped that with further research and refinement, the detection technology will be able to identify rock movement of a lower magnitude and more specifically identify the location.

As well as taking a closer look at landslides, attention has been turned to the deepest point in the ocean, Mariana Trench.

Mariana Trench in the west pacific is the deepest known sea trench. At 11-kilometres deep, and with an atmospheric pressure to match, not much is known about the organisms that inhabit its unwelcoming conditions. Food is also thought to be scarce at this depth with only 1% of organic matter reaching depths of 3-6 kilometres. Ronnie Glud and his team from the University of Southern Denmark recently set out to discover what life existed this deep under the sea and what food was there for them. They sent autonomous sensors and sample collectors down Mariana Trench. Surprisingly, organic matter was abundant at the bottom of the trench. Explanations for this include the sharp slope leading down to the often-broad sea trenches meaning that organic matter falling on the slope cascades all the way down. Though only 1% of what accumulates at the bottom of trenches may be nutritious, the overall amount of matter that ends up there means that overall, there is plenty.

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