To complete this activity, download and print the Student Question Sheet.

What is cryptobiotic soil?

Cryptobiotic soil is a descriptive name, if you speak Latin. Loosely translated it means “hidden, living soil.” Cryptobiotic, or biological, soil crusts are visible, but not many people take notice, even when they walk on them.

In this activity you will create a model of cryptobiotic soil crust and simulate two types of erosion to evaluate the importance of this hidden, living soil to the southwest desert.

Soil crusts are a combination of unrelated organisms that live together on the soil surface. “Biological soil crusts are a complex mosaic of cyanobacteria, green algae, lichens, mosses, microfungi, and other bacteria.”(1) Sometimes this living desert has a black crust. If you pour water on this black crust it will change colors in a minute or so as its photosynthetic algae and bacterial cells turn on very quickly to produce nutrients.

(1) Belnap, Jayne, Roger Rosentreter, Steve Leonard, Julie Hilty Kaltenecker, John Williams and David Edlridge, Biological Soil Crusts: Ecology and Management, 2001. Technical Reference 1730-2. U.S. Department of the Interior.