MadSci Network: Earth Sciences |
Dear John: There are both faults and earthquakes in Florida. For information about the geologic structure and hazards of Florida, and specifically faults and earthquakes in Florida, you can contact the U.S. Geological Survey (http://www.usgs.gov) or the Florida Geological Survey (located in Tallahassee). Geology departments at Florida universities should each have at least one faculty member knowledgable about these matters. So, if the information I give you here is insufficient, those are very good sources for more details. There is a former plate boundary in Florida, because most of the Florida peninsula was once part of Africa. The suture is buried quite deep, and is not a zone of active plate movement now, but there are many ancient faults associated with it. Other (newer) faults in Florida are associated with the thick sedimentary succession deposited on the western Florida continental shelf. These faults form when thick masses of sediment start to slide slowly downward because of their great and unevenly distributed weight. Earthquakes are commonly associated with movement on growth faults, as these are called. Other earthquakes may be caused by ground settling resulting from water or hydrocarbon extraction. Major earthquakes are unknown in Florida, and minor earthquakes are not common, but they do occur. The two largest earthquakes recorded in Florida, according to the US Geological Survey database, occurred in 1780 and 1879. Both measured VI on the modified Mercalli scale (used before the invention of the Richter scale). The Mercalli scale is based on human reactions and property damage; VI corresponds to "felt by all, many frightened and run out of doors." So you see, these are not major earthquakes. Most major earthquakes are associated with tectonic plate boundaries, giant bolide impacts, and volcanoes. Of these three causes, only giant bolide impacts are possible in Florida, and these are exceedingly rare (the last one was in Tunguska, Siberia, in 1908). This is why there are few earthquakes in Florida. David C. Kopaska-Merkel Geological Survey of Alabama PO Box O, 420 Hackberry Ln Tuscaloosa AL 35486 (205) 349-2852 (205) 349-2861 FAX Email: davidkm@ogb.gsa.tuscaloosa.al.us
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