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November 17, 2021
Another intersection of lidar and 19th-century observations at the Silas McDowell slide, Macon County, North Carolina
McDowell described the slide as a “violent shock” which opened a “chasm” that remained visible for many years after the initial event. The date of the slide is unknown, but it probably occurred during the 1850s.
November 2, 2021
A mid-1800s description of landslide topography meets 21st century lidar at Split Mountain, Haywood County, North Carolina
The “mystery” of Split Mountain specifically refers to episodes of falling rock, formation of lumpy “hillocks” on previously smooth slopes, split and tilted trees, and cracked ground that gave the mountain its name in the mid-19th century. Interestingly, none of the features Clingman described are readily apparent today, allowing the mystery to persist.
June 22, 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.
April 6, 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.
March 24, 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.
March 1, 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.
February 24, 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.
January 11, 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.”
December 4, 2020
Lidar hillshade imagery hints at the location of a future coal spoil landslide
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.
October 15, 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.
