Today, two GigaPans shot of the uppermost Martinsburg Formation, informally known as the “Cub Sandstone” since it crops out along Cub Run in the southern part of the Massanutten range. 10 or 15 meters upsection (west) of these two outcrops is the base of the Silurian-aged Massanutten Sandstone, the ridge-forming unit. Lower in the section: … Read more
Yesterday, I took five new GigaPans at Thoroughfare Gap, a water gap where Broad Run cuts through Bull Run Mountain, the eastern limb of the Blue Ridge Anticlinorium at my latitude. The rocks here are the Cambrian-aged Chilhowee Group, with bedding tilted moderately to the east during Alleghanian mountain-building in the late Paleozoic. To the … Read more
Callan continues his week-long recounting of his five-day backpacking trip from the Cape of Good Hope to Cape Town, South Africa, along the Hoerikwaggo Trail. Today, we examine the jointing, oxidizing and reducing fluid flow, and the emplacement of ore veins.
Last week, we took a closer look at the xenoliths (MME’s?) in the Boulder Batholith. Here is a look at a fracture, perhaps a small fault, in that same outcrop. There are no marker units by which we could detect offset here, so we can’t say for sure it’s a fault. But definitely weathering has … Read more
The Boulder Batholith outside of Butte, Montana, is actively weathering, and shedding off grus. In the third installment of the Transitions of the Rock Cycle series, we watch an igneous rock turn to sediment.
An outcrop of the Ordovician-aged Martinsburg Formation is used to illustrate the development of slaty cleavage, and hence a major transition in the Rock Cycle.
The Friday fold, delayed by a week from last week’s contest, appears in Yoho National Park, British Columbia, near the “Natural Bridge” over the Kicking Horse River.
Royal Tyrrell Museum geologist Dave Eberth donates time and expertise to help Callan’s students understand the Cretaceous-aged Horseshoe Canyon Formation in central Alberta.
A cobble of green Belt/Purcell argillite, exposed on the trail to Crypt Lake in Waterton National Park, Alberta, displaying a well-developed “weathering rind”:
Callan shares some photos of “leopard rock” (porphyritic mafic dikes) seen along the Beartooth Highway, northeast of Yellowstone National Park.
Wow! Is it Friday already? Time flies when you’re settling into your dream house. The Friday fold is of my new home, the doubly-plunging Massanutten Synclinorium: The Alleghanian Orogeny is responsible for deforming these strata. Differential weathering produced the valley/mountain/valley pattern. The Cambro-Ordovician limestones and flysch (shale + graywacke) of the Martinsburg Formation in the … Read more
A few shots from Fossil Falls, in the southern Owens Valley, California… This is the now-dry river bed of the Owens River. There’s abundant evidence of water-induced erosion (potholes, polishing, etc.), but nary a drop of water to be seen – Though this particular portion of the Owens River drainage dried up in the Pleistocene, … Read more
Here’s the view riding up (or down) Sulphur Mountain, Banff, on the gondola: As you can probably tell from the cable lines’ misalignment, this was a composite (stitched) photo. Mt. Rundle is in the background. If you turn to the left, you can see Tunnel Mountain, south of the town of Banff: Tunnel Mountain is … Read more
Some tafoni (pattern of little weathering pits) expressed on Malmesbury Group (~700 Ma) turbidite sandstones at a little outcrop on the eastern shore of False Bay, South Africa: That last one seems to have some concentric layering to the tafoni pits – exfoliation? Spheroidal weathering? Hmm…
Here are some photos out the window of my flight home from California the week before last… Snow on the north sides of mountains, but not on the south sides (view is from the south towards the north): Same thing here: And again… And again… it would appear that our route from Reno to Minneapolis … Read more
Some views from the airplane, over southern Wyoming (first two photos) and north-central Nevada (last four), last Saturday morning… A canyon: …and zooming in to the middle area of the previous photo: Strata upwarped into a structural dome (that has been “planed off” to be topographically horizontal, revealing a bull’s-eye-shaped outcrop pattern, then differentially weathered … Read more
Meter-scale fold in metagraywacke layers at the head of Mather Gorge, Maryland shore of the Potomac River, highlighted by differential weathering along the layering. Annotated interpretation: Happy Friday!
Spheroidal weathering in Kruger National Park, South Africa. This outcrop is Archean granite of the Kaapvaal Craton. It’s producing a nice little inselberg in the low veld; good klipspringer habitat. “Kopje” is the word I learned to call these things in East Africa, but I guess the proper Afrikaans spelling is “koppie.”
Another sample from the collection on display, both indoors and out, at the University of Texas at El Paso. Don’t know anything about it beyond its lovely differential weathering. Happy Friday.
I’m in El Paso, Texas, today (and tomorrow and Saturday), collaborating on a massive brainstorming session for a new NSF-funded initiative called InTeGrate, which is all about Interdisciplinary Teaching of Geoscience for a Sustainable Future. As leader Cathy Manduca said today when she opened our session, “We’re here to save the world!” And we’re going … Read more