B15K Crevasse seen from above

Such enormous icebergs as this are sufficiently stable and long-lived to have tracking and monitoring equipment deployed on them. Access is by helicopter of course as the edge of the berg presents a barrier of 10's of meters of vertical ice wall.

When overflying these bergs, you can sometimes see down deep crevasses as in this picture. Eventually some of these crevasses will cause the iceberg to split into smaller and smaller pieces.