Just Below the Surface

Geology is the study of the Earth with most people thinking instantly about rocks and minerals. Rocks and minerals are sometimes confused for each other by the public, but both have distinct characteristics that separate them. For example, minerals are solid substances that are inorganic (or not alive) and also have a definite chemical structure composed of elements such as copper, iron or silicon. Rocks, on the other hand, are composed of various minerals. For example, granite, an igneous rock, is composed of minerals like mica, quartz, and feldspar. Some rocks may even have a biological component. For example, coal is formed from decayed plant matter.

Although the Lowcountry is not a rocky area, it does have a diagnostic geology. Lowcountry geology, in this case, relates primarily to sediment layers rather than large craggy rocks. From the sand that makes up the beautiful beaches of our coast or the “pluff” mud we find in the salt marshes the sediment beneath our feet is composed of materials that once were rocks. Rivers like the Ashley and Cooper carry rocks and pebbles downstream to the ocean. As the pebbles move and impact each other, they are slowly broken up and worn down. The individual quartz grains along with other heavily weathered minerals are then deposited at the mouths of these rivers and ocean waves will then move them onto the beach.


The Charleston Museum’s newest lobby exhibit, Just Below the Surface: Digging Deep into Geology will showcase many of the rocks and minerals before this weathering and erosion has occurred. This will allow patrons to see the original state of these original rocks and minerals before forming our sand and mud.

 

– Natural History Curator Matthew Gibson