Frost line
From Free net encyclopedia
The term frost line has at least two specific, distinct meanings, from different branches of science.
"Frost line" in Geology
In geology, the frost line is the level down to which the soil will normally freeze each winter in a given area. Building codes must take this into account, as foundations must be dug down to or below this point. Failure to do so will cause frost heaving to dislodge the building at least slightly, causing damage which may become a serious threat to the building's structural integrity.
In Chicago and other locations of similar climate, the frost line is three feet-six inches, or 1.07 meters. In near-Arctic and Antarctic locations, the frost line is so deep that it becomes year-round permafrost, and there is instead a "thaw line" during the summer.
"Frost line" in Astrophysics
In astronomy or planetary physics, the frost line refers to a particular distance in the solar nebula from the central protosun where it is cool enough for hydrogen compounds such as water, ammonia, and methane to condense into solid ice grains. Depending on density, that temperature is estimated to be about 150K.
The lower temperature in the nebula beyond the frost line makes many more solid grains available for accretion into planetesimals and eventually planets. The frost line therefore separates terrestrial planets from jovian planets.