Usually found in first-year ice (cf. ridging).
melt-water has disappeared after the formation of
8.2.2.6.1 Ridged ice zone: An area in which much
cracks and thaw holes. During the period of dry-
ridged ice with similar characteristics has
ing, the surface whitens.
formed.
9.4 Rotten ice: Sea ice which has become honey-
8.2.3 HUMMOCK: A hillock of broken ice which has
combed and which is in an advanced state of dis-
been forced upwards by pressure. May be fresh
or weathered. The submerged volume of bro-
ken ice under the hummock, forced down-
9.5 Flooded ice: Sea ice which has been flooded by
wards by pressure, is termed a bummock.
melt-water or river water and is heavily loaded
by water and wet snow.
8.2.3.1 Hummocked ice: Sea ice piled haphazardly
one piece over another to form an uneven
surface. When weathered, has the appearance
10. ICE OF LAND ORIGIN
of smooth hillocks.
10.1 Firn: Old snow which has recrystallized into a
8.3 Standing floe: A separate floe standing verti-
dense material. Unlike snow, the particles are to
cally or inclined and enclosed by rather smooth
some extent joined together; but, unlike ice, the
ice.
air spaces in it still connect with each other.
8.4 Ram: An underwater ice projection from an ice
10.2 Glacier ice: Ice in, or originating from, a gla-
wall, ice front, iceberg or floe. Its formation is
cier, whether on land or floating on the sea as
usually due to a more intensive melting and ero-
icebergs, bergy bits or growlers.
sion of the unsubmerged part.
10.2.1 GLACIER: A mass of snow and ice continuously
moving from higher to lower ground or, if
8.5 Bare ice: Ice without snow cover.
afloat, continuously spreading. The principal
forms of glacier are: inland ice sheets, ice
8.6 Snow-covered ice: Ice covered with snow.
shelves, ice streams, ice caps, ice piedmonts,
8.6.1 SASTRUGI: Sharp, irregular ridges formed on a
cirque glaciers and various types of mountain
snow surface by wind erosion and deposition.
(valley) glaciers.
On mobile floating ice the ridges are parallel
10.2.2 ICE WALL: An ice cliff forming the seaward
to the direction of the prevailing wind at the
margin of a glacier that is not afloat. An ice
time they were formed.
wall is aground, the rock basement being at or
8.6.2 SNOWDRIFT: An accumulation of wind-blown
below sea-level (cf. ice front).
snow deposited in the lee of obstructions or
10.2.3 ICE STREAM: Part of an inland ice sheet in which
heaped by wind eddies. A crescent-shaped
the ice flows more rapidly and not necessarily
snowdrift, with ends pointing down-wind, is
in the same direction as the surrounding ice.
known as a snow barchan.
The margins are sometimes clearly marked by
a change in direction of the surface slope but
9. STAGES OF MELTING
may be indistinct.
10.2.4 GLACIER TONGUE: Projecting seaward extension
9.1 Puddle: An accumulation on ice of melt-water,
of a glacier, usually afloat. In the Antarctic,
mainly due to melting snow, but in the more ad-
glacier tongues may extend over many tens of
vanced stages also to the melting of ice. Initial
kilometres.
stage consists of patches of melted snow.
10.3 Ice shelf: A floating ice sheet of considerable
9.2 Thaw holes: Vertical holes in sea ice formed
thickness showing 250 m or more above sea-
when surface puddles melt through to the under-
level, attached to the coast. Usually of great hori-
lying water.
zontal extent and with a level or gently undulat-
ing surface. Nourished by annual snow
9.3 Dried ice: Sea ice from the surface of which
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