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You are browsing the archive for geology Archives - AGU Blogosphere.

31 January 2022

Thirty years on semi-solid ground

At the end of this month, Vladimir Romanovsky will retire after 30 years as a professor and permafrost scientist at the University of Alaska Fairbanks’ Geophysical Institute. This comes at a time when people — finally — no longer squint at him with a puzzled look when he mentions what he studies.

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22 June 2021

Low-displacement landslides explain unusual West Virginia landscape features visible in lidar imagery

Like so many older landslides in the Appalachians, the significance and cause of these features is unknown. Because they are so numerous and are only visible using lidar data acquired in 2016, they may represent an untapped resource of useful information about the recent history of Appalachian landscapes.

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16 April 2021

Listening to avalanches half a state away

High on the broken pyramid of Iliamna Volcano, rotten rock held in place by volcano-warmed ice sometimes loses its grip. Several times over the years, rock-and-ice avalanches have blasted down Iliamna at 150 miles per hour. Left behind on the mountain’s face is a dirty, five-mile scar, in the same place as the last one.

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6 April 2021

Central peak formation in model impact craters

I produced the model impact crater with a combination of the same granular materials I use for tectonic models and a projectile fired from a powerful air rifle (a city-safe version of Gene Shoemaker’s approach). The model crater developed a nice central peak as well as terraced margins. The darker material is quartz sand, combined with a small amount of cornmeal to produce a minor amount of cohesion between sand grains. The white material comprising the central peak is glass microbeads.

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24 March 2021

What does that landslide actually look like, part 2: an active landslide

As indicated in the previous post, lidar-derived imagery still needs ground-truthing to maximize its usefulness as a means of characterizing landslides and other slope failures. Last June, Ken Gillon and I visited the Rutherford County, North Carolina, landslide described below as part of our work with Appalachian Landslide Consultants, PLLC (ALC) on behalf of the North Carolina Geological Survey. This slide caught my eye in lidar hillshade imagery because it appeared to share characteristics with an active slide we had visited a few days before.

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4 March 2021

Finding the great earthquake of 1900

The largest earthquake on the planet for the year 1900 happened somewhere near Kodiak, Alaska, on Oct. 9. Scientists know it was big, but how big? And could it happen again?

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1 March 2021

What does that landslide actually look like?

We have no constraints on the age of the slides, but they may reflect logging history in the area. The majority of these slopes were heavily and continuously logged during the past ~150 years, with logging in this area clearly occurring within the past 50 years. The slides may have developed after clear-cuts, with the rapid return of vegetation common in the region quickly making the area look less disturbed than it really is.

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Malaspina Glacier gets up and goes

Massive icefields near the Canada/Alaska border feed Malaspina ice through a slot in the mountains. Freed of mountain walls, Malaspina’s ice oozes over the coastal plain like batter on a hot griddle. Near the Gulf of Alaska about 30 miles northwest of Yakutat, the glacier is — on clear days — visible from a window seat on an Alaska Airlines flight from Southeast Alaska to Anchorage. But the dirty-white blob on the cheek of Alaska is not as large as it used to be, which is why glaciologist Martin Truffer and his colleagues are studying it.

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24 February 2021

Lidar-derived imagery of 1949 debris flows on North Fork Mountain, Grant County, West Virginia

Debris flow events present a significant hazard to life and property in all parts of the Appalachians. The 1949 event that created the features shown here caused 8 fatalities and displaced a tremendous number of residents. Detailed mapping…along with analysis of detailed surface imagery, can greatly enhance understanding of where debris flows begin and where they travel. This understanding, in turn, can potentially reduce the human impact of these particularly dynamic and mobile slope failure events.

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8 February 2021

Blue beads in the tundra: The first U.S. import from Europe?

Glass beads the size of blueberries found by archeologists in a Brooks Range house-pit might be the first European item ever to arrive in North America, predating the arrival of Columbus by a few decades.

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11 January 2021

The Ray Sponaugle well: A 13,000-ft lesson in Appalachian Valley and Ridge structure

“To the surprise of the drillers and geologists involved with the project, the well bore never got anywhere close to the Cambrian quartzite. At 10,000 ft (3,010 m) below the surface, the well passed through a thrust fault and entered a tight, nearly recumbent syncline cored by the same Ordovician shale unit into which drilling began.”

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15 October 2020

Normal fault, reverse fault, or both?

The new model, whose color scheme is admittedly quite shocking (think Pepto-Bismol bottle), is shown… The interesting fault is at the center of the image. The fault is traced in black in the lower image, with arrows indicating movement sense.

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5 October 2020

Interesting “sideways” movement of a large sandstone blockslide

A large sandstone blockslide in Highland County, Virginia presents an unusual appearance in LiDAR hillshade imagery–it appears to have moved sideways across a slope instead of directly down the slope.

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24 September 2020

LiDAR reveals the cloth-like appearance of a “wrinkled” translational landslide

The Virginia Valley and Ridge hosts plenty of amazing landslide features, but this wrinkled translational slide in Botetourt County, Virginia is particuarly eye-catching. It reminds me of the wrinkling that might occur in a thin layer of cloth pushed along a smooth surface–something like pushing a napkin or tablecloth along a tabletop.

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14 September 2020

The interesting geologic setting of Thomas Cole’s “The Oxbow”

New from The Geo Models blog: “Earlier this year, I became aware of the longer, geographically-specific title and learned that the painting does portray a real location with a particularly interesting geologic context…. Cole’s vantage point on Mt. Holyoke is east-northeast.

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4 September 2020

#AGURocks: The Intersection of Music and Science

I didn’t start making and recording music until college, where I met some friends who had similar interests to me. They pushed me to write songs with them in a band, which was something I had wanted to do forever, but had lacked the courage to create and perform in live settings. As I progressed through my microbiology degrees, both as an undergraduate and graduate student, I used music as a way to vent about broader institutional issues I saw in the sciences.

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28 August 2020

The Geo Models: Landslides associated with historic iron mining in the Virginia Valley and Ridge

The sharpness of these landslide features suggests they may still be slowly moving, but very little disruption to vegetation is visible in satellite imagery, so movement is probably very slow. Since their maximum age is known (the time of mining; late 1800s-1920s), they offer interesting comparison to older, natural landslides in the area, which tend to have softened, rounded features due to weathering and erosion.

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28 July 2020

Fault-propagation folds in a sandbox model

New from The Geo Models: “These anticlines are recognizable as fault-propagation folds because the fault that offsets the deepest blue layer does not cut upward through the entire section. Displacement along the fault at depth is accommodated by folding of the overlying, un-faulted layers.”

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24 July 2020

Earthquake adds missing piece to puzzle

Late in the evening of July 21, 2020, State Seismologist Michael West heard a text alarm. His phone informed him of a large earthquake beneath the ocean, just south of the Alaska Peninsula, about 60 miles southeast of the village of Sand Point. His first thought was that this — the biggest earthquake on the planet so far in 2020 — would cause a devastating tsunami. His second thought was that a longstanding earthquake mystery may have just been solved.

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21 July 2020

Is this Florida’s most famous landslide?

New from The Geo Models blog: “I asked Google and was rewarded with a vintage paper called…wait for it…’A Florida Landslide.’ Written in 1948 by Richard Jordan of Florida State, the paper describes a surprisingly impressive landslide that occurred in Gadsden County, Florida…”

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