The Earth Story

This is an incredible landscape to view in the first place - the Sierra Nevada Mountains above Lone Pine California, just below Mt. Whitney - this hiker was taking panorama videos, and then an earthquake struck triggering rockfalls all around him.

Volcanic Avalanche

Volcanoes have this annoying habit of becoming unstable. They build themselves up vertically, piling up lava flows on the top of the cone, until every so often gravity wins.

Volcanic collapse happens for a number of reasons. The biggest recorded avalanche in modern history happened because of a volcano; the entire north side of Mount St. Helens collapsed in 1980 due to pressure within the volcano that was deforming the entire mountain.

Other types of collapses are associated with the building of a high peak or a lava dome. When thick, viscous lava is pushed out of a volcano, it starts building lava domes that build upwards. A big, vertical pile of rocks isn’t a stable situation and can lead to a collapse. This image from the International Space Station shows the remnants of an ancient volcanic collapse in the nation of Bolivia. The mountain close to the center of this image is called Tata Sabaya. It’s one of many volcanoes in this part of the world, occurring due to subduction off of the West coast of South America.

However, take a look to the west of this cone. First, you can see the dried, salty remnants of a lakebed called Salar de Coipasa, which was filled with water during the last glacial period (10,000 years or more ago, at the time it would have been Lago Coipasa). Today, that lake has mostly dried up, leaving a salt flat deposit…but there are all these giant pieces of rock sticking out.

These blocks are surrounded by the saline deposits, but they spread over an area of 300 square kilometers. For comparison, that’s over 3 times the size of manhattan. The largest blocks stand up to 100 meters above the surrounding terrain; basically they’re skyscrapers.

These giant blocks are the remnants of a mega-landslide. The Tata Sabaya volcano, sometime before the last glacial maximum, completely collapsed, spilling its innards to the west and into the lake. Whether this collapse happened during an active eruption or just because of gravity (or gravity + an earthquake) is difficult to tell, because all of the other remnants of this avalanche wound up in the lake and washed away. Since the collapse, the volcano has rebuilt itself into a mountain probably similar in size to what it used to be. But at least from this perspective, the remnants of this mega-avalanche are a sight to behold.

-JBB

Image source, from NASA: http://earthobservatory.nasa.gov/IOTD/view.php?id=80945

Tata Sabaya: http://www.volcano.si.edu/world/volcano.cfm?vnum=1505-032

Volcanological and petrological evolution of Volcan Tata Sabaya, SW Bolivia (subscription): http://www.sciencedirect.com/science/article/pii/037702739390043Q[_

_](https://www.facebook.com/TheEarthStory/photos/a.352867368107647/507184022675980/?type=1&theater#)

It’s rainin’ rocks

This map should make us all take a moment and go hug the atmosphere. No, you figure out how, it earned it.

When a rock enters earth’s atmosphere, it releases a lot of energy and often explodes, producing shock waves in the atmosphere that have been detected by a U.S. Government monitoring program. These events are called bolides, and this map shows the location of bolides beyond a certain size in Earth’s atmosphere over a 20-year period from 1994-2013.

This map shows a total of 556 events, basically 1 every 2 weeks, on average. The largest explosion in that time was the Chelyabinsk event in 2013, when an asteroid about 20 meters in diameter entered the atmosphere, exploded, and fragmented, damaging cities in Russia near the shock.

The smallest dots on this map are much weaker than Chelyabinsk – objects about a meter in size entering the atmosphere and vaporizing or exploding produce them. Those are pretty harmless most of the time, but they still release the same energy as 5 tons of TNT exploding. The difference between a barely-detectable blast and something that can severely damage a city, therefore, is the difference between a chunk of rock 1 meter wide versus 20 meters wide - the Chelyabinsk explosion is estimated to have released the same energy as a 500 kiloton nuclear bomb.

As Earth orbits around the sun, it is literally in a shooting gallery of debris; rocks left over from the formation of our solar system hit this planet all the time, as this map shows. The locations of these events appear random, indicating that stuff flies in from all sides with no obvious pattern. By having this data over a 20 year period, scientists will be able to use statistics to estimate how often we can expect large explosions, the scale of Chelyabinsk or larger, in the atmosphere, and use that understanding to gauge how much we need to prepare for larger impacts.

If it weren’t for our atmosphere, most of these rocks would be hitting Earth. Instead, the thin layer of air above it does a remarkable job at keeping things off our heads. We owe it some thanks for that favor.

-JBB

Image credit: NASA/JPL http://neo.jpl.nasa.gov/news/news186.html

Moraine Lake

Missing: 1 large impact crater

The rocks seen in the first couple photos are little glassy blobs called tektites. Tektites are ejecta from large impacts – when an asteroid hits the Earth’s surface, it dumps so much energy into the target rocks that some of them partially melt and some of that debris is flung out to and beyond the edge of space. Little bits of molten rock will fly through the air and form droplet, or sometimes dumbbell shapes. As they cool in the air, they can cool to glass, creating the dark black color of these samples found on the surface.

In short, they’re kind of like droplets of obsidian created by asteroid impacts. If you go to a rock show, you’ll probably find some really nice ones on sale from Indochina or Southeast Asia. In fact, that’s where all of these are from. There’s a field of really well formed tektites that runs from Southeast Asia to Australia, and samples from that area (called a “strewnfield”) are regularly collected and sold around the world.

The Indochinite tektites are some of the best-developed ones on Earth, showing the classic droplet and dumbbell shapes. In fact, I even have one on my counter. The tekites are well dated as forming during the Pleistocene, 790,000 years ago. There’s only 1 problem with these Tektites; the crater is, um, missing.

Tektites are only going to form if there’s a large asteroid impact. There should be a crater at least 10s of kilometers wide left over from the impact that formed the Indochinite tektites, but no crater is known in that area from that time. That’s too young for the crater to have been subducted so the planet can’t be hiding it that way. There are a handful of proposed sites in Southeast Asia, but a tempting idea is to put the crater in Antarctica since you could hide it beneath an ice sheet.

The final image comes from a recently published study that, unfortunately, seems to rule out Antarctica as a source for these tektites. A team led by scientists at Curtin University in Perth, Australia studied the presence of a few very tiny grains in some of these tektites, looking for minerals that only occur at extreme pressures. They found that there is a polymorph of zirconium oxide called reidite found only in tektites from Indochina itself (the star on the map). Other samples, marked by dots inside the solid circle, are the only ones that have a high-pressure form of quartz called Coesite in it. All of the pale dots are places that don’t have these high-pressure phases in them.

The geographic location of these high-pressure phases seems to imply that the crater that formed these tektites must be in Southeast Asia somewhere, as that’s where the tektites are found that were hit the hardest. Somewhere in Southeast Asia, likely somewhere in that dark circle, there is a hidden impact crater, and we still don’t quite know where.

One other interesting bit of data comes out of this study. When an asteroid impacts Earth, the bigger the asteroid is, the higher the shock pressure is. The minerals in this study only form in impacts that are of a certain size. The crater that formed these tektites, therefore, must be at least 40 kilometers in diameter, and possibly up to 100 km. That’s at least the size of the city of London. There’s a city-sized crater buried somewhere in Southeast Asia, and as of now we still don’t have a certain candidate for where it is.

Anyone have a spare city-sized crater somewhere?

-JBB

Image credits: http://bit.ly/2piB2PT http://bit.ly/2FFs9Kk

Original paper: http://bit.ly/2HGbIKs_ _

“Volcano Boarding” down loose rocky slopes, Cerro Negro, Nicaragua

PLASTIGLOMERATE – The destructive legacy of mankind

It is likely that in the next 100 000 years the modern concept of Homo sapiens that we know and love will cease to exist, just as it is difficult to fathom the everyday lives of humans from 100 000 years before us. Our early ancestors left intriguing skeletal remains, stone tools and primitive art to help us decipher their lifestyles. We are leaving behind plastic… mainly.

Plastic has become so pervasive a substance that it can be found in some of the most remote locations including untouched, pristine tropical islands and in the deepest recesses of our oceans (mentioned previously in the post: EARTH’S MICROPLASTICS PROBLEM). But who would’ve thought it would find its way into the very earth itself? In 2014, Patricia Corcoran and colleagues produced a research article on the troubling occurrence of a novel geological phenomenon in Kamilo Beach, Hawaii. Plastiglomerate is a newly classified type of rock that many believe will mark the start of the Anthropocene, or the era in which technologically advanced humans have evolved. This is because it consists of naturally occurring debris and sediment that have combined with molten plastic and hardened together to form an often colourful, rocky clump. It is found predominantly in coastal regions and is believed to form from plastic pollution in contact with lava flow, forest fires or bon fires. Kamilo Beach is different from bathing beaches where constant human influence introduces plastic regularly. It is a remote coastal stretch that experiences influxes of marine debris from a nearby gyre. Except that most recently, the debris consists of plastic in various forms. Two types of plastiglomerate were encountered, namely clastic and in situ. Clastic plastiglomerate was described as an agglomerate of basalt, coral, seashells, woody debris and sand held together in a plastic matrix. The in situ type plastiglomerate was seen as plastic debris that had adhered to rocky surfaces, or molten plastic that had filled into the gaps in volcanic rock known as volcanic vesicles, becoming a part of the landscape.

So besides being the marker of our plastic revolution, what’s the worst impact that plastiglomerate can have? The formation of plastiglomerate in Kamilo Beach is thought to be driven largely by campfires and bonfires. The burning of plastic is known to release a variety of noxious chemicals which may cause cancer and affect the endocrine system. The formation of plastiglomerate from extreme heat has led researchers to infer that volcanic activity may also promote its formation. Additionally, the near-immortality of plastic poses significant environmental implications. Plastic can take thousands of years to decompose, but the products of its decomposition and its affinity to often toxic compounds is a direct threat to marine and coastal systems. Unless we want to be remembered for our toxic contributions to the environment, we need to make some serious changes in our plastic-driven habits.

KR.

References and further reading:

http://bit.ly/2tqaNGz https://en.wikipedia.org/wiki/Plastiglomerate http://bit.ly/2upfWCO http://bit.ly/2tqvQc5

Image: http://bit.ly/2ukwtbx

Zion Rockfalls

Zion National Park in Utah is open year round, but the weather recently left many of the park’s most popular features inaccessible. Snow, ice, and rain are all common there in winter, and Zion had plenty of all three last week. The soil became saturated and went through freeze/thaw cycles that triggered rock falls.

The first landslides occurred on trails. The well-worn Lower Emerald Pools Trail was one of two trails that become impassible and had to be closed after several debris and rockfalls completed covered portions of the trail (see photo). Heavy rain also meant that popular The Narrows and other canyon trails had to be closed as well due to high water levels.

Then another landslide hit the Zion Scenic Drive dropping 200 tons of sandstone onto a section of the road about 4 car-length long (see photo), trapping 12 cars on the opposite side with no other outlet. The occupants had to temporarily leave their cars behind and take a shuttle back out of the park. Thankfully no one was hurt. It’s the second time in 5 months that rockslides have closed a road at Zion (http://bit.ly/2iKyGX9).

Geologists and engineers will help the NPS decide when and how to safely remove the debris. No work can begin until the area is determined to be stable. And while it’s sad to see a beloved park suffer damage, the NPS notes it’s a good reminder that geologic processes at the park are always on-going.

Photo Credit: National Park Service https://www.facebook.com/zionnps/ References: https://www.facebook.com/zionnps/ https://www.nps.gov/zion/index.htm http://bit.ly/2k1mfrS

Drone flight over cliffs labeled as part of Hadrian’s wall, border between Scotland and England in Roman times.

Here’s one I haven’t seen before. Perseid meteors viewed from above, from the International Space Station, 2 in about 2 seconds from the high resolution downlooking camera.

Videographer travels through Nepal to see how the country is recovering 1 year after the large Gorkha Earthquake.

Cruising down one of the eroded, sediment-lined channels in Death Valley, National Park, at low light conditions.

The gigantic Seymareh landslide - can you spot it?

The Seymareh or Saidmarreh rock avalanche is the biggest known subaerial (on Earth's land surface and exposed to Earth's atmosphere) non-volcanic landslide on Earth. With a volume of about 44 Gm3 it had a massive impact on its surroundings.

About 10 000 years ago, in the early Holocene, the rock mass on the flank of Kabir Kuh in the Zagros Mountains of Iran failed catastrophically. A huge avalanche crossed two valleys and travelled about 19 km far, damming up two major rivers. Two large lakes formed and remained intact for a long period of time until they eventually breached the natural dam and eroded a channel through it.

The slide was probably triggered by an earthquake and involved several rock layers including limestones, carbonates and mudrocks. The morphology of the debris indicates that the rock mass rapidly disintegrated and transformed into a highly mobile avalanche. The surface of the slide is now cut by ridges, troughs and large grabens and offers a spectacular example of a gigantic and ancient slide.

You can find the location of the Seymareh landslide very easily on satellite images and have a look around at the different characteristic features of a landslide by searching for these coordinates: 33°00'20" 47°35'44" or by following this link: http://bit.ly/1RsXH01.

Xandi

Image Credit: Google Earth Sources: http://bit.ly/1OV63f2 http://bit.ly/1LYg3UQ http://bit.ly/1TY3T4J http://bit.ly/1QpScRS