What is a "calving" glacier?
The coastal glaciers in Greenland, Chile, Alaska and the Antarctic come to a spectacular end, in a process called "calving".
As the glaciers flow towards the ocean they push over uneven ground.
This can create cracks, and crevasses are formed. Reaching the sea, the ice breaks off at the crevasses.
If the glacier or ice stream is still intact when it reaches the sea it doesn't break up immediately.
The waves hollow it out from below. The higher parts loose their support and fall into the ocean. This is how icebergs are created.
Icebergs are dangerous hazards for shipping and are therefore closely monitored
In the Antarctic and in Greenland, these icebergs are often the size of skyscrapers - if measured from base to top.
Did you know?
An Arctic iceberg of this kind proved to be fatal for the Titanic in 1912.
Even today, icebergs are dangerous hazards for shipping and are therefore closely monitored.
They are so massive that they can easily damage ships, and what's more, about 9/10 of their volume is under water - only the tip of the iceberg is visible.
The birth of an iceberg
The winter of 1912 was an unusually warm one, so in April there were large numbers of icebergs from Greenland floating about in the Northern Atlantic.
The wireless operator had received several ice warnings, but the Titanic did not slow down - it was considered unsinkable.
When an iceberg was sighted, it was too late: the Titanic collided with it and sank. About two and a half hours later 1,517 lives were lost in the freezing cold sea.
Via Marilyn Armstrong