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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.
6 April 2021
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.
24 March 2021
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.
24 February 2021
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.
11 January 2021
“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.”
4 December 2020
A coal spoil landslide in southeastern Wise County, Virginia, appears traceable to a faint scarp visible in the spoil pile in a 2017 lidar dataset. The slide pre-dates October 2019 Google Earth imagery and post-dates the 2017 lidar data acquisition.
5 October 2020
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.
24 September 2020
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.
14 September 2020
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.
28 August 2020
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.
28 July 2020
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.”
21 July 2020
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…”
17 July 2020
Several Mesozoic rift basins have been exhumed along the Atlantic margin of North America, creating interesting patterns in sedimentary rock layers and igneous intrusions that originated during the breakup of Pangaea.
1 July 2020
A new study simulates ocean tides on imaginary Earth-like worlds, revealing the limits of topography’s influence on tidal energy
19 June 2020
The latest post from The Geo Models blog.
15 May 2020
A simple model of a continental rift basin that develops some characteristics of the real thing can be made by constructing a layered sand cake on top of two overlapping sheets of paper, one of which is anchored to the underlying board, etc. This model setup will produce an asymmetric half-graben style of basin, which has a single, high displacement breakaway fault on one side and several smaller faults on the other.
22 April 2020
Latest from from The Geo Models: Deformation associated with listric (downward flattening) normal faults produces very interesting patterns.
7 April 2020
The different mechanical properties of the layers are apparent in the dip angles of the normal faults in the model. The master fault on the left side of the model (black line) is less steep in the weak microbeads, an expression of how their failure behavior differs from the stronger layers above and below.
25 March 2020
Some upper Devonian sandstone mountains in the Virginia Valley and Ridge show evidence of deep-seated landsliding, resulting in the formation of a downthrown block (graben) along the summit ridge.
20 March 2020
A newly-released LiDAR data set reveals impressive ridge-top cracks associated with large rock slides in the Virginia Valley and Ridge. While the cracks are easily visible with LiDAR hillshade imagery, they appear to be covered by normal forest vegetation and would probably look like elongated depressions in the forest.