#7 Note the several erosion gullies here. Water running off Sulphur Spring Road has eroded deep ditches (up to six feet) where the soil is sandy or gravely. On the other hand, in some places there is very little erosion. Invariably, these places have clay soils and rock just under the surface of the ground. Several remarkably different soil types underlie CERA, reflecting the complex geological history of this area near the junction of the Piedmont and Coastal Plain physiographic provinces.