Geology thread

[bjdeming]

Meanwhile, in Arkansas, posted about two hours ago -- proof that cool geology stuff is not just about shakin' and bakin':

 

[bjdeming]

Seismic "CT" of the upper crust underneath the US (scale is too large to pick out regional and local features):



A little more info here.

That could be the old Farallon plate (a real troublemaker) whose tail end -- now called the Juan de Fuca plate -- is still subducting under our feet here in the Pacific Northwest, storing up more stresses for the next "big one."

 

[bjdeming]

FIrst impressions on the terrible landslide in Papua New Guinea, from the AGU's landslide blogger, Dave Petley; there have been some strong quakes in the general region lately, but he doesn't think seismicity was a factor (of course, this could change as more information gets out -- in good times, it's difficult to get near-real-time news from this remote country);

On first inspection, this is a large rock slope failure that has transitioned into a rock and debris avalanche. There has been no indications that there was a trigger event, such as intense rainfall or an earthquake. It will be interesting to see whether the slope had been subjected to mining or quarrying. Note the very steep, planar surface at the rear of the landslide scar, and also on the left side. This suggests to me that the landslide has mobilised existing planes of weakness in the rock mass.