Thaw depth Thaw depth In soil science, the thaw depth or thaw line is the instantaneous level down to which the soil has warmed to zero degrees celcius. The active layer thickness is the maximum thaw depth over a period of two years. The layer of soil over the thaw depth is called the active layer, while the soil below is called permafrost. The term frost front refers to the varying position of the thaw line during the periods of freezing/thawing. The knowledge of the thaw depth is important for the two major reasons: its influence on the ecology and on construction
San Joaquin (soil) San Joaquin (soil) San Joaquin is an officially designated state insignia, the state soil of the U.S. state of California. The California Central Valley has more than 500,000 acres (2,000 km²) of San Joaquin soils, named for the south end of that valley. This series is the oldest continuously recognized soil series within the State. It is one of California's Benchmark Soils, and a soil profile of it is displayed in the International Soil Reference and Information Centre's World Soil Museum. The San Joaquin series became the official state soil on August 20, 1997, the result of efforts by students