Boudinage is such a fun structure. Here’s an example from the roadcut adjacent to the quarry featured so heavily last week. The thick limestone stratum in the center of the photo has been stretched left-to-right. It exhibits pinch-and-swell structure, the first stage of boudinage. Small extensional fractures began to form in the boudin necks, accommodating … Read more
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
The initials ABE might make you think of Lincoln, but that’s not what I’m talking about. Today, the letters mean something else: three subdivisions of the 5-part Bouma sequence of turbidites. I took these photos on a new (to me) outcrop of the Ordovician-aged Martinsburg Formation in Page County, Virginia. I visited the site for … 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
A USGS colleague shows Callan a bizarre fold outcrop in the Conococheague limestone of the Boyce quadrangle, Virginia.
Yesterday, I worked on my sabbatical project, the Mid-Atlantic Geo-Image Collection (M.A.G.I.C.). Whether I go outside on a given day to shoot GigaPans of local geology depends on multiple factors: (a) How’s the weather? (b) Do I have to watch Baxter? (c) Can I bring Baxter with me? (d) How are the lighting conditions? Yesterday … Read more
Everything’s bigger in Texas, even the footprints…
Some of the dynamics of small-scale mass wasting in granular materials are captured in this animated GIF from sand dunes in Death Valley.
This image is from the canyon in which route 168 ascends the Inyo Range from Big Pine, California. View is to the south/southwest. Those are gravel layers that dip gently westward. I think they’re associated with the underlying Waucobi Lake Beds, which are Plio-Pleistocene in age. The lake beds are made of finer stuff, but … Read more
All seen last March in Death Valley, at Mesquite Dunes…. within ten minutes of one another.
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 Table Mountain Sandstone.
Here’s a terrific outcrop to start off the new year at Mountain Beltway. We’re back in the Bighorns of Wyoming here, on highway 16, traversing the southern portion of the range en route from Buffalo to South Pass City. Click to enlarge Annotated, expanded, and Easter-egg-embedded: Click to enlarge From a different perspective (uphill a … 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.
My students Alan Pitts, Chris Johnson, Robin Rohrback and I have been busy adding to the Mid-Atlantic Geo-Image Collection. Check out a few of these new GigaPan images: link link link link link link link
What are these students up to? I’ll give you a hint: this is Dinosaur Provincial Park in the Great Plains of southern Alberta. The badlands style topography here offers a nice vertical section through clastic sedimentary rocks originally deposited adjacent to the Western Interior Seaway. On our Canadian Rockies field course in July, my co-instructor … Read more
NASA’s Earth Observatory posted a colorful confluence image last Thursday, and it reminded me that I have a similar site of my own to share. This is on the Icefields Parkway, north of the Athabasca Glacier and Snow Dome, a hydrological drainage triple point. Here, we’re a short distance into the Arctic Ocean drainage. (West … Read more
A weekend expedition to GigaPan the C&O Canal’s singular Paw Paw Tunnel results in an exposition on Devonian sedimentation, Alleghanian mountain-building, structural geology, and the incision of the Potomac River to produce entrenched meanders.
A few photos from the Canadian Rockies illustrated the characteristic “look” of glacial striations. Callan also demonstrates how they can be used for outright tomfoolery.
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.
The Friday fold is a seaside outcrop of soft sediment deformation (not post-lithification tectonic deformation) on Kodiak Island, Alaska.