The state's carbonate rock is filled with more than 4,000 caves

The state's carbonate rock is filled with more than 4,000 caves, ten of which are open for tourism.[22] The Virginia seismic zone has not had a history of regular activity. Earthquakes are rarely above 4.5 on the Richter magnitude scale because Virginia is located away from the edges of the North American Plate. The largest earthquake, at an estimated 5.9 magnitude, was in 1897 near Blacksburg.[23] A 5.8 magnitude earthquake struck central Virginia on August 23, 2011, near Mineral. The earthquake was reportedly felt as far away as New York City and Toronto, Canada.[24] Coal mining takes place in the three mountainous regions at 40 distinct coal beds near Mesozoic basins.[25] Other resources such as slate, kyanite, sand, and gravel are mined, with an annual value over $2 billion as of 2006.[26]


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