Tag Archives: landslide

ESA/Rosetta/NavCam

Landslide spotted on comet for the first time using Rosetta’s images

A 100-meter cliff on Comet 67P was caught by the Rosetta’s spacecraft’s cameras as it dramatically collapsed. It’s the first time a landslide on a comet was documented.

ESA/Rosetta/NavCam

This image taken on July, 2015, shows a white outburst emanating from comet 67P. The bright flash is radiating ice exposed by a cliff which collapsed. Credit: ESA/Rosetta/NavCam

A while ago, Maurizio Pajola, an astronomer at the Nasa Ames Research Center, California, was up late at night casually browsing images taken by the famous Rosetta spacecraft when he came across something strange. He saw a bright patch emanating out of the comet’s dim surface in a photo taken by ESA’s spacecraft in December, 2015. So Pajola went through the catalog of images that focus on the region in question, a cliff called Aswan. He eventually came across an image snapped in on July 10, 2015 were a large plume of dust was showing. A snapshot taken just five days later clearly showed the cliff had collapsed, linking the bright outburst to the landslide. In the wake of the landslide, a giant 70 metres-long by one metre-wide fracture was carved.

When the cliff collapsed, it exposed a patch of pristine ice which radiated strongly which explains the bright features at the top of Comet 67P that Pajola had initially witnessed.

A 70 metre-long, 1 metre-wide fracture was created in the wake of the cliff's collapse. Take a moment to appreciate how sharp these images are -- taken by a spacecraft orbiting a freaking comet millions of miles away from Earth. Credit: ESA.

A 70 metre-long, 1 metre-wide fracture was created in the wake of the cliff’s collapse. Take a moment to appreciate how sharp these images are — taken by a spacecraft orbiting a freaking comet millions of miles away from Earth. Credit: ESA.

Previously, scientists had thought such outbursts, seen before in other comets, were the result of pressurized gas that blasted through the comet’s warm interior. Now, astronomers need to rethink the mechanics of such events often observed in comets which come too close to the sun.

In the same study published in Nature Astronomy, Pajola and colleagues simulated the conditions on the surface of the comet at the time when the cliff collapsed. Around July 2015, temperatures sharply rose from an ungodly -143 degrees Celsius to scorching 46 degrees celsius in only 20 minutes as the comet dropped from the shadow and came face to face with the sun’s rays. Every 12 hours, the cliff was directly exposed to the sun for one and a half hours. This tug of war of expansion/contraction triggered by the temperature gradients eventually cracked the cliff causing it to collapse.

“This is the most compelling evidence that we have that the observed outburst was directly linked to the collapse of the cliff,” said Maurizio Pajola, an astronomer at the Nasa Ames Research Center, California, and the study’s lead author.

The findings yet again confirm that comets aren’t just benign chunks of dust and ice — they’re very much geologically active, Pajola says. Cliffs collapse, boulders roll, dust migrates all the time. There are even sinkholes. A lot of things are happening.

After two years spent orbiting around comet 67P, which culminated with landing a robotic probe on the comet’s surface, the 12-year-long mission came to an end last year, in September. Data gathered by the probe, such as the high-resolution images analyzed by Pajola and colleagues is still keeping scientists busy, however. Science will likely benefit from Rosetta for another decade underscoring its importance.

Landslide fatalities continue at Burma jade mines

The annus horribilis continued at the jade mines in Myanmar, as another major landslide was announced, with at least one fatality and ten people missing.

While local reports seem sketchy and unreliable, it seems that it’s yet another case of a collapse of a waste pile onto informal miners who scavenge the dumps. The local Irrawaddy news service cited a police officer Tuesday:

“The landslide moved slowly, so most of the people working on the waste pile had time to run for their lives,” he said. “According to witnesses, he fell down from a cliff and was buried deeply,” he added, warning of the threat of more landslides in the area. Khin Maung, a miner who witnessed the collapse, told The Irrawaddy that around 20 people had been mining for jade residue at the time of the incident. “The waste pile slowly slid down, with people shouting and running away. Some escaped, but some did not,” Khin Maung added.

The Hpakant area of Burma has suffered a string of disastrous landslides this year, with a disturbingly high number of fatalities.

Table via AGU.

Table via AGU.

 

Over 300 lives lost in a single year, from landslides that could have likely been avoided, or at the very least been mitigated, is an unacceptable number. But why is this happening now, has something changed recently? According to a fascinating article on the Human Rights Watch website, the main culprit is a blatant disregard for the workers’ health, despite skyrocketing profits:

The miners were working at a site used by dozens of Burmese and Chinese companies that have dramatically increased mining in the past year, driving many small-scale miners to scavenge for small jade deposits the machinery misses, in dangerous dump sites where landslides are common. Since large-scale mining resumed in 2014, profits have skyrocketed, but that has done little to reduce the threats to miners’ safety.

Mining companies should be held responsible for the health and safety of their workers, because until then, the number will probably continue to grow. It’s easy to blame all this on illegal mining scavenger, but the reality is that the companies operating the mines should ensure the safety.

Jade trade in the Burma area of Myanmar is one of the significant sources of income, especially in the poorer areas. The jadeite deposits found in Burma’s northern regions is the highest quality Jadeite in the world, so high that some people can even survive by scavenging the remains around the mines. The mining process itself was not without danger. Much of the jade extraction is done by “boulder mining”, which requires removing the “overburden” layer of alluvial material, exposing the rocks below, and separating the jade containing rocks, while discarding the waste in a river. Irresponsible dumping could very well be responsible for these landslides.

 

Colorado Mudslide seen from outer space

A month ago, on May 25, a large mudslide rushed down a Colorado mountain near the town of Collbran covering an area three miles long and one-half to three-quarters of a mile wide. It claimed the lives of three ranchers, caused a small earthquake and covered an area three miles long and one-half to three-quarters of a mile wide.

You can see the huge extent of the mudslide in the pictures above, which was taken by the Landsat 8 satellite on June 7. The lower image, taken by Landsat 8 on June 20, 2013, shows the slide region before the slide; on average, Colorado experiences thousands of landslides each year, but very few reach this magnitude. This region in particular, the Grand Mesa region of western Colorado, is extremely prone to landslides due to the underlying geology.

What we have there is a heavy layer of basalt ontop of soft claystone that erodes easily. When the water starts to erode the claystone, the basalt above starts to slip, catching more and more mass in its movement; the phenomenon is more prone in the spring, when there is a large quantity of water around from meltoff and increased rainfall.

Image via Baum and Odum, 1996.

The slide contains a pool of water at the top, and a large block of earth towards where the slide originated. Geologists now estimate that pool will hold about 245 acre feet of water before it could reach an outlet and spill over