These crusts play an important role in the ecosystems in which they occur. Cyanobacteria, previously called blue-green algae, are one of the oldest known life forms. It is thought that these organisms were among the first land colonizers of the Earth's early land masses, and played an integral role in the formation and stabilization of early soils. The earliest cyanobacteria fossils found are called stromatolites, which date back more than 3.5 billion years. Extremely thick mats of these organisms converted the earth's original carbon dioxide rich atmosphere into one rich in oxygen and capable of sustaining life.
Cyanobacteria occur as single cells or as filaments.
The most common form found in Colorado Plateau soils are the filamentous type, which are usually surrounded by sticky, mucilaginous sheaths. When moistened, cyanobacteria become active, moving through the soil and leaving a trail of sticky material behind. The sheath material sticks to surfaces such as rock or soil particles, forming an intricate web of fibers throughout the soil. In this way, loose soil particles are joined together, and an otherwise unstable surface becomes very resistant to both wind and water erosion. The soil-binding action is not dependent on the presence of living filaments.