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You are browsing the archive for structural geology Archives - Page 2 of 3 - AGU Blogosphere.

4 December 2019

There are tension gashes in my yogurt (but I ate it anyway)

As a student, I thought the gash patterns were great, but I always struggled to understand their relationship to shear zone orientation in the context of the stress field…This is where the yogurt comes into play. Some very nice en echelon tension gash sets appeared in my Greek yogurt a few weeks ago when I squeezed the plastic container.

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30 October 2019

“Oreo cookie” stratigraphy and the geologic setting of the Frog Legs Gorge

While the “frog legs gorge” post was supposed to be a bit funny, the real purpose of it was to link outcrop patterns with geologic structure. This follow-up post tries to put the frog legs’ underlying structure into a broader context within the Appalachian Valley and Ridge…

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22 October 2019

Google Earth and a simple model explain a weird pattern seen in LiDAR hillshade

Is this a bizarre and gigantic fossil discovery? An unsolved mystery akin to the face on Mars? Unfortunately, this is just another set of compressional folds within the Appalachian Valley and Ridge, but they do stand out in the hillshade due to their interesting topographic pattern.

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8 October 2019

An interesting geothermal energy prospect in the Vienna Basin…and its connection to oil and gas

In effect, the hydrogeothermal project is doing just what oil and gas exploration does–looking for and extracting desirable fluids in the subsurface. In this case, the desirable fluid is hot and readily flowing water…

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5 August 2019

Toreva Block landslide models

Somewhere on the AGU Landslide blog, I came across a reference to another type of rock strength-controlled, intact landslide I had never heard of–the Toreva Block. Like the Appalachian Valley and Ridge giant landslides, it is possible to replicate Toreva-style movement with contrasting model materials that represent failure-prone shale and much stronger topography-supporting lithologies, like sandstone or basalt.

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10 July 2019

Using sand models to explain the concept of geologic mapping

Geologic maps can be very visually engaging, but non-geologists may find it difficult to extract the information that a map is supposed to communicate…. Cross sections included with a map can help, but it can still be tough to pull it all together if you don’t look at this sort of material all the time.

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29 April 2019

The landslide that is too big to notice

The southeast slope of Sinking Creek Mountain in Craig County, Virginia hosts what is certainly one of the largest landslide complexes in eastern North America–and possibly the least noticeable. Despite extending for 15 miles (25 km) along the mountainside…this group of translational blockslides was not documented until 1986 by Art Schultz of the USGS.

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25 March 2019

A sandbox model perspective on the tilted sedimentary layers of the eastern Rocky Mountain Front Range

One of my earliest recollections as a geology student was a discussion of the upturned sedimentary rocks in The Garden of the Gods at the eastern foot of the Rocky Mountain Front Range in Colorado. I distinctly remember hearing about the vertical movement of a large block of crust, which would ultimately produce the high mountains, tilting the overlying sedimentary layers out of its way as it rose.

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26 February 2019

Some examples of the geology of “gaps” and travel on the early American frontier

The topographic features of the Powell Valley Anticline (PVA) played a significant role in the lives of both indigenous and Euro-American peoples on the American frontier in the late 18th century… Here I focus on two subjects inextricably connected to PVA topography: The Wilderness Road and Robert Benge, also known as Chief Benge, Captain Benge, Bob Benge, or simply “The Bench.” Benge and Wilderness Road users had two very opposite goals, leading to numerous clashes and Benge’s ultimate demise in the mountains of the PVA.

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15 February 2019

A LiDAR perspective on a 1965 geologic map

…how much existing geologic maps, particularly those produced without any digital topography or remote sensing, could be enhanced by checking them against LiDAR hillshade. The answer varies, and to continue the Powell Valley Anticline discussion, I draped a 1965, hand-drafted geologic map over the new LiDAR hillshade background.

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12 November 2018

Tectonics, heavy rain, and the cross section of nightmares

A YouTube viewer asked if I could make this style, which is strongly associated with parts of the sub-Andes fold-thrust belts in Colombia and southern Peru. I looked at some papers and gave it a shot!

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6 November 2018

Resurrecting buried faults along Jamaica’s south coast

In this model, I tried to reproduce a structural style that it is clearly expressed in some very interesting landforms–the Santa Cruz and Don Figuerero Mountains of southern Jamaica.

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24 October 2018

Geologic context of the “bottomless” plunge pool at Bath Fountain, Jamaica

I stuck my iPhone (in a Lifeproof case) into the pool with the camera recording video to see just how deep it was. For whatever reason, I didn’t look at the video while I was at the pool…I wish I had.

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2 October 2018

Model impact craters, from a structural geologist’s perspective

I have always wondered what would happen if the sandpacks I use for structural models were struck by a high-velocity projectile. This turns out to be a fairly easy question to answer if you have sand and a quality pellet gun…

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21 September 2018

Cove Mountain looks like a “2”…Part 3 (or Geology is even bigger than it looks!)

…large plunging folds make interesting shapes in erosional landscapes.

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6 August 2018

Normal or reverse? Tricky interpretations near high-displacement faults

I made this little compressional wedge model to test the mechanical contrast between various sands. The results weren’t quite what I was hoping for, but one very interesting geometry occurred just below the “backstop” thrust sheet.

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25 July 2018

A “duct tape and WD-40” approach to digital topography and geologic mapping

By Philip S. Prince Google Earth is amazing, but sometimes tree cover and land use obscure subtle but significant surface features critical to mapping and interpretation. Digital elevation and terrain models provide a way around this, but without ArcScene, SketchUp, or a similar program they lack the 3-D reality of Google Earth in oblique perspective. Addtionally, hillshade terrain models can produce an inversion effect for observers when seen in plan …

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17 May 2018

Making a new map of Denali

A Fairbanks scientist recently made an intricate new map of Denali while crisscrossing its summit a few times in a single-engine airplane.

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30 April 2018

Cove Mountain looks like a “2”…Part 2!

Recreating the evolution of the Cove Mountain “2” with Play-Doh.

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16 April 2018

Cove Mountain looks like a “2,” even to a structural geologist…but why?

Cove Mountain is shaped exactly like a neatly drawn “2.”

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