An experiment showing how ground cracking takes place due to the intrusion of magma. The black material at the bottom would represent the dyke. From USGS, Mastin, L.G., and Pollard, D.D., 1988, Surface deformation and shallow dyke intrusion processes at Inyo Craters, Long Valley, California: Journal of Geophysical Research, v. 93, no. B11, pp. 13,221-13,235.