Marine Ice-cliff Instability

Ice cliffs are produced when the ice shelf disintegrates because of bottom melting, where warm ocean waters seep beneath the ice sheet causing it to melt from the bottom up, and/or hydro-fracturing, where the ice sheet is destabilised because of cracks in its internal structure. If the cliff is tall enough (about 100m of ice above the water line), the stresses at the cliff face exceed the strength of the ice. This causes the cliff to fail structurally, leading to ice breaking off from the edge of a glacier— a process known as glacier calving. 
 

Credits: Muhammad Hadi Ikhsan/ Earth Observatory of Singapore.