As temperatures begin dropping with the approach of the cold weather months, in many parts of the world a rare, natural phenomenon may begin to occur. Characterized by sudden, loud rumbling or “booms” accompanied by ground shaking, it often leaves those who have experienced it confused, or even badly frightened.
“Frost quakes,” also known as cryoseisms, are a natural phenomenon that occurs when extremely cold temperatures lead to sudden deep freezing of the ground, after it has been saturated with water. The Vermont Geological Survey defines a cryoseism as, “[a] major frost cracking of the top few feet of the ground, occurring during sub-zero cold snaps, which generates localized ground shaking and is often mistaken for an earthquake.” (1) Expansion that results during the process of freezing can lead to the buildup of explosive stress, which may result in fractures within the earth. Small cracks may be visible on the surface near where a cryoseism has occurred, and in some cases, shaking vibrations may also be felt within the vicinity of the frost quake, along with loud booms that sound similar to gunfire. (2)
The National Oceanic and Atmospheric Association (NOAA) reported that the winter of 2013-2014 ranked among the coldest on record, particularly in parts of the American midwest. (3) The following year, more record cold temperatures began to occur in November of 2014, as a result of early-season arctic air and snow. (4) These recent temperature drops coincided with an increase in reports of loud noises of unexplained origin, as well as what some believed to be small earthquakes, which were being reported across the country.
Often described as loud booms similar to the sound of an explosion nearby, reports of these “mystery booms” were frequently shared and discussed through social media sites. Numerous media outlets featured the stories as well, which helped spur interest in the potential causes of the phenomena.
Despite the new attention this phenomenon has recieved, cryoseisms have been recognized as a geological phenomenon for many years, and significant data about their occurrences and underlying causes has existed for a number of decades. (5) Some sources suggest that among the variety of causes for tremors, geocryological causes were suspected by as early as 1818. (6) However, the record cold temperatures associated with the winters since 2013 have led to significant interest in the subject, leading some to speculate that a correlation may exist between reports of loud “booms”, frost quakes, and climate change. Previous scientific data has already suggested that reports concerning a related phenomenon (see below) may be increasing along with rising temperatures around the world. (7)
Sudden movements or shifts in glacial formations are linked to another variety of cryoseism, which have been called “ice quakes”. These similar, but very distinct phenomena were first revealed through the detection of low-frequency seismic signals, appearing mostly during summer months, which geophysicists traced to the movement of glaciers in Greenland. (7)
Sounds associated with frost quakes
It has been suggested that at least a fair majority of “mystery booms” reported in cold weather months are the likely result of cryoseisms, though in some cases, other explanations have included sounds produced by aircraft, military weapons tests, and even recreational use of fireworks. Alternatives such as these remain prevalent in various media appearing online, due to continued reports of unexplained noises that linger beyond the cold weather months in various locations. For more information about unexplained sounds that may not be related to cryoseisms, visit this link.
- John E. Ebel, Richard Bedell & Alfredo Urzua. “A Report on the Seismic Vulnerability of the State of Vermont”. Geology of Mineral Resources, Vermont Geological Survey. July 1995.
- “Cryoseisms (or frost quakes) in Maine.” Maine Geological Survey, October 6, 2005. http://www.maine.gov/dacf/mgs/hazards/earthquakes/quake-cryoseism.htm
- “NOAA: Winter 2013-2014 Among Coldest on Record in Midwest; Driest, Warmest in Southwest.” http://www.weather.com/news/news/winter-ncdc-state-climate-report-2013-2014-20140313
- “November 2014 Shattered Cold and Snow Records For Some.” http://www.weather.com/storms/winter/news/november-2014-cold-snow-records-us
- D.E. Willis, R.W. Taylor, M. LeNoble, & S. Yellin. “Icequake Precursors”. 51st Annual Meeting of the Eastern Section of the Seismological Society of America. Dept of Geological Sciences, University of Wisconsin–Milwaukee. October, 1979.
- Andrew V. Lacroix. “A Short Note on Cryoseisms”. Earthquake Notes, January 1980.
- Tom Irvine. “Ice Quakes.” Vibrationdata Newsletter, June 2006. http://www.vibrationdata.com/Newsletters/June2006_NL.pdf