Incredible video of houses in Norway sliding into the ocean on a mud layer.
Source: vgtv.no
Learn about Lahars - mudflows generated naturally by volcanic structures and events.
earthstory reblogged
Geologic heroin at the Pallisades of John Day Fossil Beds Nat'l Monument, Clarno Unit, OR.
A volcanic complex to the south produced prodigious ash fall and tuffs. Over time these slid away in lahars or welded into ignimbrite. In this area this led to huge, well-stratified, windswept cliffs that include many fossils, mostly petrified wood and leaf impressions. This is the Pallisades Mudflow Member of the Clarno Formation (57-40 Ma or so)
Mudflow in Stehekin, Washington
On the shores of Lake Chelan in a remote area of the state of Washington sits the city of Stehekin, a small town of 150 which is effectively only accessible by boat or floatplane. The town sits in an area mostly managed by the federal government, within the Lake Chelan National Recreation Area and just south of North Cascades National Park. Since the area is managed by the park service, we can share some of their impressive photos taken following a mudslide in this area. This photo shows what used to be a road.
A combination of large wildfires and large rainfalls triggered this particular slide. The mud poured through the town, carrying boulders and trees with it, eventually dumping out into Lake Chelan which sits at the bottom of the valley. Although several businesses were damaged, no one was injured in this slide.
-JBB
Image credit: National Park Service http://www.flickr.com/photos/northcascadesnationalpark/9695877144/in/set-72157635421195577
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earthstory reblogged
Mud volcanoes of Qobustan. Baku, Azerbaijan.
Incredible video of a debris flow captured in the Swiss Alps (I think). Note how the edges and front have built up extra-coarse grained material, a common feature in these sorts of debris flows. Also note that it isn’t raining at this site - this debris flow formed from rocks and water being dislodged farther up slope, so remember that as a hazard warning in mountain valleys.
This series of frame captures from NOAA’s GOES-WEST weather satellite gives a satellite-eye view of the train of El Nino driven storms, an atmospheric river type event, that slammed into California over the last week.
earthstory reblogged
Recent mudslide/debris flow deposits in Tehachapi, CA Photo 1&2: notice the disappearing fence line Photo 3: debris in the bush Photo 4: 10 ft buried drainage catch
Overflight video of the end result of one of those mudslides like we saw in the last video, this one showing what happened where it crossed a road. Cars and trucks tossed around and buried beneath each other.
This is drone-captured video of a mudflow/debris flow advancing its way down a canyon in the California desert. Great video.
California has been in a drought for years, but this year’s strong El Nino event is likely to replace that drought with heavy rains. Heavy rains, of course, have their own risks, such as this amazing series of on-site videos of a mudflow engulfing vehicles on a highway in the high desert near Tehachapi.
A few days ago I shared these images of a massive and deadly flash flood in Utah that struck Zion National Park and other parts of southern Utah. This video was captured by a hiker escaping that same flood.
This video captures the major mudflow and flash flood in Utah and Arizona at a different location from the last video. This mudflow was deadly, several people died near here and a group of climbers in a slot-canyon in Zion National Park also were caught offguard and killed.
A couple days ago southern Utah and Arizona were hit by a deadly flash flood that killed over a dozen people. Here’s on-site video of part of the flash flood view downstream (NSFW Language). The power of the flood is extraordinary - just carries a couple cars downstream like they’re nothing.
This news reel footage captures the beginning stages of a landslide in Japan’s Kagoshima Prefecture. Watch how the trees are carried with the slide as it starts off moving as a single mass that broke away before it then disrupts and turns into a mudflow.
Sabo dams
Mountainous areas of the world have major threats towering over them; sometimes during heavy rains the mountains will come down.
A debris flow is a fast-flowing mixture of rock, water, mud, and sand that flows rapidly downhill under the force of gravity. Debris flows can engulf villages and cities rapidly, sometimes with little to no warning. The energy of the flowing water is dangerous enough, but the large chunks of rock can be particularly hazardous as they’ll plow right through a person, car, or house.
Sabo dams (also called check dams) rely on technology that has been in use around the world for thousands of years. Today dams like these are most commonly deployed in Japan, a country that has to deal with the combined threats of debris flows, tropical storms/typhoons that can trigger flooding, and volcanic lahars, although other Sabo dams have been deployed in a variety of locations around the world.
The idea behind a Sabo dam is pretty simple. If a stream is flowing normally, the stream should be allowed to continue flowing. It should be able to carry its normal sediment load downhill, eroding and depositing normally, without having sediment pile up behind the dam where it could be a threat to its integrity. A Sabo dam therefore is a structure built around a stream that lets the stream flow through during normal times. It can be something like this – a metal grate across the stream – or a concrete structure with a channel in the center that allows for normal river flow.
In the event of a flood, debris flow, or lahar, suddenly the dam’s presence becomes known. If the water level on the stream rapidly increases, suddenly the vertical bars are in the way. Friction with the vertical bars will actually slow the speed of the water rushing in the flooding river and as the water is slowed, some of the sediment will drop out behind the dam. Furthermore, if the river begins carrying large objects such as boulders or felled trees, those objects will be fully trapped behind the dam and will actually interrupt the flow even more.
These structures can be built at many scales; even small, temporary structures placed in the path of a river likely to flood can serve as obstacles that protect people downstream (based on my reading, small/temporary structures generally are described as check dams, although the terms can be interchangeable).
These structures can be particularly useful in areas at risk of Lahars. Lahars are volcanic debris flows and mudflows that can occur catastrophically. Volcanoes tend to be high peaks and therefore can generate snow and glaciers, they tend to have layers of poorly consolidated rocks and ash that are easily eroded away, and they also have heat supplies that can suddenly cause glaciers and snow to melt. Lahar threats from the volcanoes in Japan are another major reason why that country has deployed these structures in a number of areas.
-JBB
Image credit: machmud junus http://www.panoramio.com/photo/39889532 https://machmudjunus.wordpress.com/2009/05/11/sabo-2/ (broken link at this page)
Read more: http://www.sabo-int.org/dott/ http://staff.civil.uq.edu.au/h.chanson/sabo.html http://bit.ly/1SWC7Vn http://on.doi.gov/1QqifpH http://www.dpri.kyoto-u.ac.jp/
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EROSIVE FLOW OF LAHAR: the Mount St. Helens eruption of 1982
The famous 1980 eruption at Mt. St. Helens, located in Washington state, blasted a caldera directly into the peak of the iconic volcano. However, this image shows the aftermath of a more minor volcanic explosion that occurred in the March of 1982.
The visible black ash shown flowing down the mountain side is actually lahar. This mudflow is constituted primarily of pyroclastic material. Pyroclastic rocks, usually ejected from the volcano, are simply various forms of volcanic rock ranging in size. Mixed with water, this mass of pyroclastic material forms a massive tide of moving "cement", capable of vast destruction and pollution. Lahar tends to obliterate obstacles in its path, known for carrying boulders as wide as 10 meters.
As you can see, the path of this destructive lahar becomes larger in width as it nears the base of the volcano. Pyroclastic mud flow tends to do this, as the steady flow of lahar builds on itself by eroding further rock fragments on the mountainside. Gorges were found at the base of the volcano due to the lahar's erosion, one gorge even dubbed the "mini-Grand Canyon." Lahar is a common result in many stratovolcano eruptions due to its steep structure, intensity of explosion, and large quantity of loose rock debris.
Lahar flow causes serious ecological harm to the surrounding environment. Think of it as a natural oil spill. The pyroclastic sediment infiltrates the areas water system and surrounding land, destroying plant and animal life. In this image, lahar is seen entering Spirit Lake, at bottom left. Following this explosion, lahar took over the North Fork Toutle River, and followed the natural river flow until lahar reached the Cowlitz River, an astounding 80 kilometers away! Lahar is an amazing observation of the natural world, yet is extremely harmful as it can destroy a diverse field of life, can block tributaries, and strip the land of its trees and soil.
Sam J.
Image Credit: Tom Casadevall, United States Geological Survey
References:
http://volcanoes.usgs.gov/volcanoes/st_helens/st_helens_gallery_28.html
http://volcanoes.usgs.gov/hazards/lahar/index.php
http://www.icr.org/research/index/researchp_sa_r04/
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