Three new videos from Montana
I spent several enjoyable weeks in Montana last month, and shot some new video content there for my YouTube channel. Here are three videos that may be of interest to readers of this blog:
primary structures
Pillbug tracks in ash from Mt. St. Helens
Reader Nancy Weidman (who supplied the Wind River boudinaged basaltic dike images from earlier in the week) sent me this interesting note: Your ichnoanalogue post reminds me of the insect or pillbug tracks I found in Mt. St. Helens ash deposited in Missoula, Montana. At least some of the tracks, if I recall correctly, ended … Read more
The coastal section at Esterillos Oeste, Costa Rica
Callan documents a geological stroll along the coast of Esterillos Oeste, in central southern Costa Rica, investigating the sequence of sediment in the Punta Judas Formation (Mid-Miocene) exposed there. Fossils, sedimentary structure, diagenetic features, structural deformation, and modern weathering all make prominent appearances.
Well-preserved mudcracks in Belt argillite, Glacier National Park, Montana
Fresh from the field, Callan shares a quintet of beautifully preserved desiccation cracks in Mesoproterozoic Belt Supergroups sediments, exposed in Montana’s geological gem, Glacier National Park.
Friday fold: blueschist & eclogite at Jenner, California
A pre-Fall Meeting field trip to the coast of northern California yields rare sights of garnet-bearing blueschist, plus eclogite, some pillow basalts, birds, waves, wind, and a lot of rain.
Friday fold: Calafia State Beach
The Friday fold is a guest contribution to “Mountain Beltway” from the manager of the AGU Blogosphere, Larry O’Hanlon. It shows apparent crumpling of a few sedimentary layers at the toe of a soft sediment slump at Calafia State Beach in southern California.
Digital manipulation as a teaching aid
Photoshop is a powerful image editing program. Its “cloning” tool allows the removal of “distracting” data from geological imagery. Examine these four examples and consider the ethical limits of the technique. Is it okay to remove fractures and lichens from an outcrop photo in order to allow novices to focus on the geological content you want them to learn from?
New discoveries in the Martinsburg Formation
A virtual field trip to examine some deepwater clastic sediments shed off the first phase of Appalachian mountain building, and deformed in the third phase. It’s a lovely day for a field trip to the late Ordovician!
Dalradian schist at Glen Roy
We saw last week how glaciation carved out a valley in Scotland called Glen Roy. As the glacier ground into the landscape, it liberated tremendous numbers of sedimentary particles from the bedrock, which is composed of Dalradian metamorphic rocks (mainly porphyroblastic schist in my observation). Then once that now-U-shaped valley had been deglaciated, a new … Read more