Geo-pic of the week: Ripple marks

Ripple marks are sedimentary features formed by water flowing over sediment.  They form in different environments including river channels, beaches, and just about anywhere water flows.  You probably saw some the last time you walked along a creek.

As water flows over sediment, it sweeps some of the loose sediment along in the direction of the current.  As the sediment migrates, it forms miniature dune-like structures.  These features are short on one side and tall on the other. The tall sides point in the direction the water was flowing.  In this case, it flowed into the picture, or away from us.

Ripples like these often get destroyed before they ever harden into a rock, but occasionally they get preserved.  Ancient ripples serve as clues to the environmental conditions that existed in a place in the distant past.  These ripples formed in what was once a deep ocean trough near Hot Springs, Arkansas .

Geopic of the week: Salt

Everyone is familiar with salt, but have you ever seen it up close?  The picture above is a magnified image of table salt.  Notice that each piece is a near-perfect cube.  This is no coincidence.  Salt, which has the chemical formula NaCl (sodium chloride), is a mineral and as such, it has a regular internal structure (a crystalline structure).  The arrangement of the atoms that make up salt form cube-shaped molecules; when a piece of salt is broken down into smaller fragments, it tends to break into cubes.

Salt is not currently produced commercially in Arkansas, but there are abundant salt deposits in the state both at the surface and underground.  Salt from shallow wells in Saline County was produced locally by settlers to the area in the early 1800’s, and by Native Americans prior to that.  The majority of Arkansas salt is extracted with petroleum from deep wells in southern Arkansas.