File:VernalPool.jpg

Summary

Vernal pools are seasonal wetlands that form only in regions where specialized soil and climatic conditions exist. During fall and winter rains typical of Mediterranean climates, water collects in shallow depressions where downward percolation of water is prevented by the presence of a hard pan or clay pan layer (duripan) below the soil surface. Later in the spring when rains decrease and the weather warms, the water evaporates and the pools generally disappear by May. The shallow depressions remain relatively dry until late fall and early winter with the advent of greater precipitation and cooler temperatures.

Copyright status

This image is public domain because it was used from the U.S. fish and wildlife services.

Source

http://www.fws.gov/oregonfwo/FieldOffices/Roseburg/VernalPools/default.asp