Bioturbation (Anthill)

Sediment is not a dead zone of eroded mineral fragments waiting to become rock again. It becomes home to living things like these red ants, which excavated about a liter of sand and silt from deep in the soil of the Mojave Desert. Their work is an example of bioturbation, a significant geologic process on land and the seafloor.

Prospectors can sometimes find clues in anthills and gopher burrows, since they sample minerals from the ground below. In desert areas, these animals may dig several meters down in search of cool air and moisture.

Bioturbation is a recent development in Earth history. It was not until early in the Cambrian Period some 500 million years ago that seafloor organisms began living in the mud, eating it for sustenance like today's earthworms. And until the Silurian some 100 million years later, no animal of any sort lived on land. After that time, the soil and the seafloor mud has almost always been subjected to bioturbation. In detailed fossil studies, especially of the marine microfossils so important to climate researchers and the oil industry, a certain amount of blurred boundaries must be expected and accounted for.

In rocks younger than Cambrian, the absence of bioturbation is a signal of dire times. After the great Permian-Triassic mass extinction there was none for millions of years.

Fossils
Geologic Features and Processes
Glaciers and Ice
Landforms
Minerals
Rocks
Geology and Society