FROSTQUAKES
If the just plain **** cold isn’t bad enough, don’t be surprised if you find yourself rolled out of your bed some frigid night in what felt like an earthquake.
Frostquakes may feel like a typical tectonic earthquake – there may be shaking, there may be rattling, books might fall from shelves, there might be things that go boom in the night; most frostquakes occur between midnight and dawn. Frostquakes can reach what feels like a magnitude 4 on the Richter scale, though they are so localized that they fail to show up on seismographs. A bit more technical sounding term for this phenomenon is “Cryoseism” (from the Greek, Kryo for cold, and “seismos” for earthquake).
Frostquakes are caused by the freezing of subsurface water. Water turning to ice is a powerful agent of a geologic process (ice fracturing) that can force (http://tinyurl.com/nsctgau) rocks to crack, mountains to split, and exfoliation of solid stone surfaces. When water that is present in shallow soils and sediments or in cracks and fissures in the ground freezes, it gains ~9% in volume when it becomes ice. This expansion can occur abruptly in extremely frigid temperature conditions, even explosively, and cause fracturing in the shallow subsurface. This sets off shockwaves that act the same as seismic shockwaves.
Cryoseisms are also phenomena that accompany glaciation, but since this cold snap is not expected to last long enough to blanket Ohio with rivers of ice, be thankful that we haven’t got THAT ****ing cold enough yet!
Annie R
Photo: by Anna Batsi with a bit of editing by me.
http://gizmodo.com/it-was-so-cold-in-canada-the-ground-exploded-1496252183 http://www.ohio.com/news/break-news/cold-temperatures-believed-to-have-caused-frost-quakes-in-northeast-ohio-1.457680 http://www.bbc.co.uk/news/blogs-magazine-monitor-25620598 http://blogs.discovermagazine.com/d-brief/2014/01/07/frigid-temperatures-trigger-rare-frost-quakes-in-u-s-and-canada/#.Us0XbZ6Sx8E