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April 16, 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.
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.
September 14, 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.
August 28, 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.
July 28, 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.”
July 24, 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.
July 17, 2020
Anticlines and synclines in exhumed model rift basins
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.
May 15, 2020
A simple rift basin sandbox model with normal faults
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.
