How do icebergs form?

Glaciers form on land as a result of an accumulation of snow over thousands of years. Successive layers compress earlier accumulations until, at depths below 60 to 70 metres, glacial ice is formed. Glaciers “flow” or “creep” outward under their own weight like a viscous fluid. When the edge of a glacier advances into the ocean, the pieces that break off are what we call icebergs.

How do Icebergs form?