A long-continued, extremely slow vertical instability of the crust, as in the
volcanic district west of Naples, Italy, where the Phlegraean bradyseism has
involved up-and-down movements between 6 m below sea level and 6 m above over
more than 2,000 yr (Casertano). Etymol: Greek "bradys" (slow) + "seismos"
(earthquake). AGI
Source:
Dictionary of Mining, Mineral, and Related Terms
