Icebergs that originate from near the bottom of a glacier; the color is usually black from trapped rock material or dark blue because of old, coarse, bubble-free ice; they sit low in the water due to
the weight of the embedded rocks.
The second adiabatic invariant is associatedwith periodic bounce motion of charged particles trapped between twomagnetic mirrors on a magnetic field line. The second invariant, termed J,is defined by
using the integral J = m ∫ v|| * ds where m is themass of the charged particle, v|| is the particle velocity along the fieldline, and ds represents elemental arc lengths along the field line. Thesecond adiabatic invariant is conserved as long as changes in the backgroundmagnetic field occur at time scales much longer than the bounce time of thecharged particles.
The surface separating the glacier from its surroundings. The term is often simply a synonym of glacier margin or glacier outline, but it can be useful to have a separate word that is understood to en
compass the glacier surface and the glacier bed as well.