dropstone
1. A clast, released by melting from the base of a floating ice sheet or glacier, which falls through the water body to settle in muddy sediment. Dropstones can often be recognized as isolated, coarse clasts set in fine, laminated sediments.

2. A volcaniclastic bomb (see VOLCANIC BOMB), ejected from a volcano, which falls into water and settles in muddy sediment on the lake or sea floor.

dropstone A rock fragment, released by melting from the base of a floating ice sheet or glacier, or a bomb ejected by a volcano, which falls through the water body to settle in muddy sediment.