The Friday fold is a lovely little sandbox analogue model by Prof. Marco Martins-Ferreira, who posted it on Twitter this week: As deformation proceeds, you can see the layers develop folds that then morph into faults, shoving deeper layers atop more shallow strata. As a bonus, you can hear Marco’s baby cooing in the … Read more
The Friday fold shows disharmonic crumpling in marbles of the Boyden Cave Root Pendant in California’s Sierra Nevada. The GigaPan image displayed is part of the digital legacy of Ron Schott, who passed away a year and a half ago.
Reader John Christian shared these folds with me via email last week. They are quartz veins in slightly metamorphosed Precambrian igneous rocks found near Sunflower, AZ in the Mazatzal Mountains. The second photo is a close-up shot of the curviest, cleanest batch of folds from the first shot. These are beautiful examples of folds in … Read more
A roadside boulder in the Bronx shows folded gneissic banding. It’s another guest-submitted Friday fold!
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.
This week marks the launch of a new digital revision of a field guide to the geology of San Francisco, “Streetcar 2 Subduction.” Learn more here!
From a creek bed in northern Colorado, the Friday fold distorts foliation in early Proterozoic quartzofeldspathic gneiss, peppered with small almandine garnets.
The Friday fold is a slab of banded iron formation now dwelling in the University of Washington’s Department of Earth & Space Sciences. But where did it come from? India? Brazil? Perhaps you can help identify its provenance.
The western edge of O’Shaughnessy Boulevard, near Glen Canyon Park in San Francisco shows beautiful examples of crumpled cherts. Here are a few dozen photos of these glorious outcrops, and instructions on how to visit.
At Bacon Cove in eastern Newfoundland, there is a nice example of an angular unconformity between Ediacaran and Cambrian sedimentary rocks.
The Friday fold erupted out of a volcano, completing the second part of its two stage cooling history, then later got folded and metamorphosed. It was found atop a high cliff near the northern Newfoundland town of St. Anthony.
The ‘Friday fold’ shows gorgeous conjugate sets of kink bands transecting the plane of foliation in some phyllitic metasediments seen on the southern Burin Peninsula of Newfoundland.
Traveling in Newfoundland, Callan visits a seaside outcrop showing a Proterozoic submarine slump complex, overprinted by tectonic cleavage and weathered by the sea.
Last weekend was the annual meeting of the eastern section of the National Association of Geoscience Teachers. On Friday afternoon, we visited Harpers Ferry, West Virginia, and my colleague Beth Doyle led a great field trip to examine the rocks exposed there. This was my favorite outcrop we saw: Here is a close up of … Read more
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?
A book review of one of the runners-up for this year’s Pulitzer Prize for general nonfiction: Elizabeth Rush’s chronicle of modern sea level rise.
When a dike is subjected to shear, how does it deform? A guest Friday fold from Darrel Cowan of the University of Washington teaches a nice little lesson. Join the field trip in Monarch Canyon of Death Valley National Park…
The Friday fold can be found in a boulder of gray chert layers on Black Sands Beach, at Marin Headlands in California.
For the third Friday in a row, “Mountain Beltway” features folds from Angel Island, in northern San Francisco Bay, California, This time, it’s meta-cherts on Perles Beach, showing impressive metamorphic recrystallization reactions.
