Weatherwatch: when cold makes the earth move
Residents of Ozaukee County, Wisconsin have been startled by a loud growth with no seen supply final Saturday. Some even reported that home windows rattled and their homes shook. What felt like a miniature earthquake was really a cryoseism, or frost quake.
Cryoseisms have been documented since the early 19th century. They are brought on by an explosive launch of stress underground, when water which has drained into cracks in rocks expands because it freezes. Under most circumstances this enlargement causes frost weathering, solely widening cracks and progressively breaking apart uncovered rocks. During a cryoseism the stress is launched , when a big part of rock or frozen soil fractures beneath the pressure.
These quakes are uncommon as a result of they seem to require particular circumstances: saturated floor and a speedy drop in temperature. These permit the water on high to freeze first, capping the water beneath in order that stress can construct up because it freezes.
While frost quakes have an effect on a small space in comparison with earthquakes, they are often intense, inflicting plaster to fall and shifting furnishings inside buildings. However, there was no reported structural harm from the Ozaukee quake.