Here's why:
* Gravity: Glaciers are formed by the accumulation of snow over time, which compresses into ice. The sheer weight of the ice puts pressure on the glacier's base, causing it to flow downhill due to gravity.
* Internal Deformation: Even though the movement might be slow, the ice within the glacier deforms and shifts under the pressure.
* Basal Sliding: In some cases, glaciers can also slide on a thin layer of water or meltwater at their base. This can cause them to move even faster.
What you might be thinking of:
* A glacier in equilibrium: A glacier can be in a state of equilibrium where the amount of snow it accumulates each year equals the amount of ice it loses through melting and calving (breaking off chunks of ice). This doesn't mean the glacier isn't flowing, just that its size and position remain relatively stable over time.
* A glacier that is retreating: A retreating glacier is shrinking due to melting and calving at a rate faster than it is accumulating snow. Even though it's retreating, it is still flowing.
So, to answer your question directly, there's no such thing as a stationary glacier. All glaciers move, even if the movement is slow or not readily apparent.
