It seems possible that a sinking current of cooled mantle material on the upper side of the plate might be the cause of such deep basins.

A small current made her feel as though she was sinking into her bed; a little more had her floating close to the ceiling or seeing her legs kicking towards her face.

Each device has an eight-bit CMOS shift register and CMOS control circuitry, eight CMOS data latches, and eight bipolar current-sinking Darlington output drivers.