Short answer
A glacier is land ice that persists and flows under gravity. An ice sheet is a vast continuous mass of glacial land ice, covering a continental-scale area. Antarctica and Greenland have ice sheets; a mountain-valley glacier is much smaller. 1 2
An ice sheet is a very large form of glacier or glacial ice mass, distinguished by scale.
On this page
At a glance
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| Question | Glacier | Ice sheet |
|---|---|---|
| Where it forms | On land | On land |
| Scale | Can be relatively small | Continental scale |
| Movement | Flows under gravity | Also flows under gravity |
The table summarizes the cited definitions and the article’s stated scope. 1 2
What each thing is
Glacier. A persistent mass of land ice that moves under its own weight. 1
Ice sheet. A continental-scale mass of glacial land ice that flows outward over a broad area. 2
Key differences
The shared material and motion explain why an ice sheet can be described as a huge glacial mass. The name ice sheet adds a scale criterion and a broad landscape form. An iceberg is different: it is floating ice that broke from land ice. 1 2
How to tell them apart
First ask whether the ice is on land and moving over time. If it is, glacier is the broad category. If the continuous land-ice cover spans a continental-scale area at a continental scale, ice sheet is appropriate. A floating block is not an ice sheet. 1 2
Where they overlap
Both store freshwater as land ice, accumulate snowfall and flow under gravity. Both can calve icebergs at marine margins. 1 2
Edge cases
An ice cap is also broad land ice but below the ice-sheet size threshold; classifications at intermediate scales involve convention. A retreating ice sheet can feed outlet glaciers, so geographic parts may carry different names. 1 2
Why the distinction exists
Cryosphere researchers distinguish scales because continental ice masses affect sea level and climate differently from a single valley glacier, while sharing physical glacial processes. 1 2
Common misconceptions
Ice sheets are not frozen ocean surfaces. Sea ice forms from seawater and floats; an ice sheet rests on land. 1 2
Examples
A valley glacier moving down a mountain is a glacier. The Greenland Ice Sheet is an ice sheet and also a mass of glacial land ice. 1 2
Sources
Sources checked October 3, 2026.
- National Snow and Ice Data Center — Glacier Quick Facts. What is a glacier?; What is an iceberg?.
- National Snow and Ice Data Center — Ice Sheet Science. What is an ice sheet?.