Invasive Gastropods in High Rock Lake, NC

High Rock Lake is one of several impoundments on the Yadkin-Pee Dee river system in the North Carolina Piedmont. Flat Swamp Creek is, or was, a tributary to the Pee Dee River. After the High Rock reservoir filled Flat Swamp Creek became a narrow, northeast-trending arm to the larger lake. This arm is so linear because it follows a geologic contact between metasedimentary rocks to the east and metavolcanic rocks to the west. The stratification in these rocks is tilted by folding, and differential erosion created narrow ridges and valleys. Flat Swamp Creek occupies one of those valleys.

At the Flat Swamp access area off Highway 8 the shoreline is littered by abundant gastropod shells. These are the remains of an invasive snail Bellamya japonica. It’s reported that their presence is the consequence of snail farming (they are pretty large). The day I was there in February, 2018, the waterway was hosting hundreds of water birds.

During low water, there are great exposures of stratification and cleavage in tuffaceous siltstone and sandstone of the Cid Formation. Nearby, to the southwest and below the High Rock dam, there are volcaniclastic rocks in the Flat Swamp member of the Cid Formation. This formation and the adjacent older Tillery Formation are part of the Ediacaran to Cambrian Albemarle Group in the Carolina Terrane. These are peri-Gondwanan sequences, attached to Laurentia (ancient North America) only since the Ordovician period.

All photographs ©Andy R. Bobyarchick.

flat swamp access

Flat Swamp access area at sunset. This is a popular swimming and boating area in summer.


Gulls huddling on perimeter floats around the swimming area.

Sedimentary bedding under shallow water at the Flat Swamp access area.


A closer view of bedding.

three shells

Evacuated and beached shells of B. japonica.

B. japonica.

many shells

A wave-washed collection of B. japonica shells.

tree roots

Life is hard for a sweetgum tree when the water level fluctuates.


Sunset across Tuckertown Reservoir below High Rock dam at the Bringle Ferry Road access area.

Sand and Ripples in the Pee Dee River

Ripples are periodic waveforms throughout the natural environment. These subaqueous asymmetrical wave ripples in sand under the Pee Dee River in North Carolina are created by oscillatory wave motions normal or slightly oblique to the shoreline.

shoreline features on the Pee Dee River, Morrow Mountain State Park, NC

Sand bar, shore line, subaqueous ripples and tree stump on the Pee Dee River, Morrow Mountain State Park, NC. This photograph ©Andy R. Bobyarchick.

Needle Ice: A Gallery

Needle ice forms in porous, wet soil or sediment when the soil temperature is above freezing and the surface atmosphere temperature is below freezing. Permeability is important. Capillary action pulls water up toward the surface where the water freezes at the bases of growing ice crystals. The growing crystals are capable of lifting small particles and vegetation above the normal soil surface. This differential motion can thoroughly disaggregate and disrupt the upper several centimeters of the soil profile in temperate climates.

The images in this gallery were made in an elementary school yard where patches of bare soil are exposed. By the time I walked over the yard, the sun had melted most of the crystals except for those protected by shadows. Most of the single, larger grains on top of the crystals are coarse sand, perhaps around 2 mm (millimeters) in diameter.

All photographs in this post ©Andy R. Bobyarchick.


cluster of mostly standing needle ice crystals

This is a cluster of mostly standing needle ice crystals. Some of the crystals have toppled over as they began to melt. It’s likely that these crystals grew during a single freeze and growth event. In clusters with multiple growth events, there is often an intermediate layer of soil particles embedded across the axes of the crystals.

photograph of needle ice

Bundles of needle ice crystals in this cluster have fallen in different directions, probably oriented toward the least resistance or toward first melting. Some of the crystals have become detached fibers.


crystals with bubbles

If you look closely, you can see that many of the needle ice individuals have longitudinal trains of bubbles. These may be air bubbles released as the crystals warm up and expand, or trapped during crystal growth. Whatever they are, the bubbles enhance the intricate internal structure of the crystals.

tilted crystals

As though swept over by a wind, these translucent, melting crystals all tilted in the same direction, roughly toward the east. It may be that eastern members of the cluster melted earlier in the day (this image was made at 1:29 PM), creating space for these crystals to fall.


fibrous crystals

Here are some fibrous crystals, all fallen but many retaining their sandy caps.

crystals with parapets

Here is a very close view of a crystal forest with sand parapets overlooking great chasms.


deep canyons

Into the deep canyons you go.


needle ice streamlet

Here is a streamlet of needle ice not quite frazil ice. This cluster did grow in a small gully, perhaps with a fair amount of water in the soil at the time of freezing. Several of these crystal streams have deep axial rifts. It could be that the thalwegs of these little streamlets were too saturated to allow crystal growth. It did not appear that the rift floors had been modified by crystal growth.

school yard

This is the setting of the ice palaces. Not very impressive at this scale, is it? That’s because the most beautiful complexity in geology in the field is sometimes only visible in the Underworld – that diminutive realm within our vision but not often visited.


Carter, J. R., 2013, Flowers and ribbons of ice: American Scientist, v. 101, p. 360-369.
Li, A., Matsuoka, N., and Niu, F., 2017, Frost sorting on slopes by needle ice: A laboratory simulation on the effect of slope gradient: Earth Surface Processes and Landforms, p. <xocs:firstpage xmlns:xocs=””/>. 10.1002/esp.4276
Li, A., Matsuoka, N., and Niu, F., 2018, Frost sorting on slopes by needle ice: A laboratory simulation on the effect of slope gradient: Earth Surface Processes and Landforms, p. n/a-n/a. 10.1002/esp.4276
Soons, J. M., and Greenland, D. E., 1970, Observations on the Growth of Needle Ice: Water Resources Research, v. 6, no. 2, p. 579-593. 10.1029/WR006i002p00579
Yamagishi, C., and Matsuoka, N., 2015, Laboratory frost sorting by needle ice: a pilot experiment on the effects of stone size and extent of surface stone cover: Earth Surface Processes and Landforms, v. 40, no. 4, p. 502-511. 10.1002/esp.3653

Needle Ice in a Loamy Soil

Needle ice in a loamy soil in a schoolyard near Salisbury, NC. The individual particles on top of the needles are coarse sand in size. Needle ice forms when soil water moves upward under capillary pressure and freezing when it contacts cold air. I will be posting a gallery of images with context on my blog soon. (The server is having intermittent problems right now.)

Tectonic Architecture

“Tectonic” as an adjective or “tectonics” as a noun refers to the large-scale structure of Earth’s crust and lithosphere. Outside of geology, the word tectonic may refer to a building or construction. The concept arrived in geological sciences prior to “plate tectonics”, mainly with application to  mountain building. The word is derived from Greek tektonikos or tekton, a builder or carpenter. Tectonic has been co-opted to indicate a rapid or global shift in, for example, policy.

According to Google’s Ngram Viewer, in English the occurrence of “tectonic” peaked about 1986. (This could be an artifact of the indexing process. Ngram Viewer operates on the corpus of terms collected by Google’s algorithms and at the time of this writing the corpus is updated to only 2008. Nonetheless, it’s an interesting pattern.)

“Architect” is a compound word from Greek arkhitektōn (chief builder). The connection is clear: architect and tectonic refer to the same underlying concept, that of structure or construction.

Now there is a phrase “tectonic architecture” that describes tectonics in architecture. Here is how Robert Mauldin described the concept in his 1986 master’s thesis at MIT.

Tectonics in architecture is defined as “the science or art of construction, both in relation to use and artistic design.” It refers not just to the “activity of making the materially requisite construction that answers certain needs, but rather to the activity that raises this construction to an art form.”

Tectonics in architecture emphasizes the constructional craft implicit in architectural design. Kenneth Frampton’s book Studies in Tectonic Culture is sub-titled The Poetics of Construction in Nineteenth and Twentieth Century Architecture. Thus the link between the constructed and natural environments.

In architecture and construction we often emulate both structure and materials as they are in the geological world.

Bridge over the Pee Dee River, NC.

Bridge over the Pee Dee River, NC. 1/250 sec at f/2.2. ISO 25, 4.15 mm, iPhone 6s Plus back camera

Long ago in a galaxy far away…

Well, you have to start somewhere, don’t you? This isn’t the beginning. It’s just a place in time, or maybe a coordinate in space-time, when the world around you seems gigantic. The hill is a mountain, the ground is a rolling ocean of green. We are ultra cool with a stick and overturned wagon. Shades. The family’s underwear flapping about in a southern winter’s wind. You don’t know that you are part of a continuum. Returning via Google street view, it’s a micro-verse, but the house (that you can’t see here) is there and recognizable and so is the hand-built garage. And the hill, and the grass. We are still there, and here, too.

A stick and a wagon and a house on the hill.

Facebook Images

I lack enough creativity to distribute my photographs in some intelligent way, so you can find a number of photo albums on my Facebook page. Here’s a current list of the main albums below. The links will transport you to the relevant album. Many of the images don’t have much of an explanation; that’s what this website is here to do.

  • Of Geological Interest – I move images that have some kind of geological impact, however remote, here.
  • Nature – This is a home for images outside of geological ones.
  • FungusAmongus – Yes, I like to make pictures of fungi. What else can I say?

There are many more there.

First Post

More or less. There were posts to an earlier version of the Geologist’s Pick back when it was partly designated to service a university-level class. (See the Colophon for a little history.) That was before Facebook, Twitter, and the tsunami of social media onto our shores.

This site – it’s blog and everything else – are a reflection of my interests in this world and the next. First and foremost is geology and all things related to geology. But it also features photography, films, and just about anything I think about. I’ll use categories for most posts, so you can filter in only those topics you want to see.

Thanks for visiting. Rock on.