Meander and Point Bar in Flat Creek, SC

Flat Creek southeasterly through Lancaster County, South Carolina. The stream feeds into Lynches River, that farther southeast joins the Great Pee Dee River. The Pee Dee joins the Waccama River at Georgetown on the SC Atlantic Coast.

Flat Creek carries a heavy load of sediment. Where this image was made, the stream crosses the Pageland granite, a pluton that is about 300 million years old. The granite is coarse-grained and sheds considerable quartz and feldspar grains as it weathers and erodes.

This image is a 180° panorama around a meander bend in Flat Creek. Lower water velocity on the inside of the meander causes the coarser sediment load to drop out to form a sandy point bar. The near bank of the river is being undercut by erosion on the outside of the meander where water velocity is greater. In time, the stream channel will migrate toward this cut bank.

It’s difficult to see in the shadows, but in the lower left corner of the photograph a tributary trickles into the main channel, and there are abundant beaver tracks there. Beavers use the tributary mouth as a slide.

In the lower right corner of the photograph you can see a boulder of Pageland granite. It’s rounded shape is characteristic of spheroidal weathering of a larger mass of granite bedrock.

Not far to the southeast, Flat Creek crosses from Piedmont igneous and metamorphic rocks into sedimentary rocks of the Sandhills.

This image was made late on a Spring afternoon under a brilliant blue sky reflecting off the water’s surface and under the long shadows of hardwood trees yet to put out theire leaves.

This image is ©Andy R. Bobyarchick

meander and point bar
A meander bend and point bar in Flat Creek near Taxahaw, SC.

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.)