Read the following paragraph and answer the question. Give ONLY the answer, no other words or explanation.

For example:

Answer: <most likely answer, as short as possible>.

Paragraph: 
Glaciers form only on land because water is too warm. When a glacier flows into water, it usually breaks up into icebergs. Those icebergs eventually melt into the water.


Question: What keeps glaciers from forming in water?
warmth
Water temperature.