Friday fold: ptygmatic vein from Finland (NMNH)

Happy Friday! Here’s a sample from the Smithsonian Institution’s National Museum of Natural History in DC: As the label says, we have a nice example of ptygmatic (“intestine like”) buckle folding here. It comes from Finland. The coarse equigranular crystals in the vein appear to be mainly potassium feldspar and quartz. The surrounding matrix has … Read more

The bizarre world wherein we march for science

I marched on Saturday. In spite of the congested conditions in both the local atmosphere and my sinuses, I felt compelled to add my voice and presence to the March for Science, an event that was probably the first of its kind since the Enlightenment, aiming to push back against anti-science attitudes from the current … Read more

Norman Bowen’s papers

I got a special treat the week before last – one of my students this semester works at the Geophysical Laboratory of the Carnegie Institution in Washington, DC. During our unit on igneous rocks, he was prompted by the “Bowen’s reaction series” discussion to let me know that Norman Bowen’s notebooks were still extant at … Read more

The Sykesville Formation, in 6 new GigaPans

As part of my work on the GEODE project, I’m always looking for good imagery to teach key concepts in geoscience. One important concept that I’ve been thinking about lately is the principle of relative dating on the basis of inclusions. Just as you can’t bake a loaf of raisin bread without already having raisins … Read more

The Smithsonian Castle and the Seneca Quarry, by Garrett Peck

The Smithsonian Castle is one of the most striking buildings on the National Mall in Washington, DC. One reason for this is its distinctive architecture, but a second reason is its color: a bright, deep red. This color comes from the rock from which the Castle constructed: the Triassic-aged “Seneca Sandstone,” a part of the … Read more

Strained metaconglomerate in Klingle Valley, DC

Following on yesterday’s post about the kink bands within the strained metagraywacke of the Laurel Formation in DC, let’s take the opportunity today to go to Klingle Valley, site of a different facies within the Laurel Formation: a strained metaconglomerate. Though the exposure isn’t as great as the Purgatory Conglomerate, I think you’ll find plenty … Read more

Kink bands in highly strained Laurel Formation, Rock Creek Shear Zone, DC

Last week before GSW, I spent several pollen-choked hours in Rock Creek Park, GigaPanning some of the rocks of the Rock Creek Shear Zone. Here are some exposures in the bed of Broad Branch that show lovely kink banding. In at least one spot, you can see a conjugate pair, so these rocks were (1) … Read more

“Outcrops” on the barn at Peirce Mill, DC

The Friday before last, I was in DC for a fun geology/botany field trip, and I got the opportunity to stroll around the barn at historic Peirce Mill, a historical grain mill along Rock Creek in Rock Creek Park, Washington, DC. The barn is immediately south of Tilden Street NW. It appears to have been … Read more

Skunk Cabbage

On Friday, I took a field trip to DC with Geologic Map of the Washington West Quadrangle author Tony Fleming, City of Alexandria Natural Resource Specialist/Plant Ecologist Rod Simmons, and a host of interested folks from many different professions and localities. We were interested in looking at ecological relationships between rocks and plants, and had … Read more

Damage to the Ecuadorian Embassy

My wife Lily is an Ecuadorian citizen. She was born in Quito, and we have traveled there together. (She’s also a U.S. citizen.) After the big earthquake on Tuesday, significant structural damage was reported at several Washington landmarks including the Washington Monument and the Smithsonian Castle. Another one, less recognizable to most folks, but key … Read more

DCSWA tour

Yesterday, I took about fifteen members of the DC Science Writer’s Association on a walking tour of DC’s geology. I was honored to present the capital city’s epic geologic story to an esteemed crowd of professional science writers from Nature, Science, the National Academies, the National Institutes of Health, the Washington Post, and other institutions. … Read more