Seracs and Icebergs

Seracs and icebergs are blocks of ice that have detached from the main glacier.

Seracs

Seracs at sunrise on the Emmons Glacier (Mt. Rainier National Park, Washington)

NPS Photo/Ryan Volum

Seracs often detach from the glacier in sections of steep ice (see ice falls). At ice fall base, compression and thickening of the ice often reincorporates seracs into continuous glacier ice. Seracs can also form by a process called dry calving at the glacier terminus. In this case, they melt in place. If they are covered in debris after breaking off, they can form depressions called kettles that sometimes fill with water.

Icebergs

A scientist kayaks among the jumbled icebergs at the terminus of Grinell Glacier as she uses a GPS unit to record the glacier's extent (Glacier National Park, Montana)

USGS Photo

Icebergs form when glacier ice breaks off into a water body—a process known as “calving.” They are not made from sea ice but instead are chunks of glacier ice that formed on land.

To learn more about glaciers, glacier features, and glacial landforms, see the Glaciers & Glacial Landforms Page.

Related Links

• NPS—Geoscience Concepts
• NPS—Geologic Tour
• NPS—Geodiversity Atlas
• NPS—Geology