Page 196 - (DK) Ocean - The Definitive Visual Guide

194 POLAR OCEANS

Icebergs

ICEBERGS ARE HUGE, FLOATING chunks of ice Iceberg Properties
that have broken off, or been calved, from the
Icebergs consist principally of frozen fresh water,
edges of large glaciers and ice shelves. These
with no salt content. This is because they originate
chunks range from car-sized objects to not from seawater but from glaciers or ice shelves
vast slabs of ice that are bigger than some (floating glaciers), and glaciers themselves come
from compacted snow. Typically, an iceberg has
countries. It is estimated that each year 40,000
a temperature of about -4 to 5˚F (-15 to -20˚C)
to 50,000 substantial icebergs are calved from at its core and 32˚F (0˚C) at its surface. In addition
the glaciers of Greenland. A smaller number to ice, some icebergs contain rock debris. This
is material that has fallen onto the parent glacier
of gigantic icebergs break off the ice shelves
from surrounding mountains, or frozen to
around Antarctica. Surface currents carry ICEBERG PROPORTIONS the glacier’s edges, and eventually becomes
Because pure ice is 90 percent as dense
icebergs away from their points of origin as seawater, an iceberg made entirely of incorporated into the ice. An iceberg’s rock load
into the open ocean, where they drift and ice will have only 10 percent of its mass affects its buoyancy. An iceberg with a high rock
visible above water. content may float up to 93 percent submerged.
slowly melt. They can last for years and are
a considerable danger to shipping.

RANGE OF SHAPES
OCEAN ENVIRONMENTS Sizes and Colors PINNACLED IRREGULAR TABULAR
Icebergs come in a range of shapes
including tabular (flat-topped),
Icebergs include pieces of ice that are hundreds
domed, pinnacled or pyramidal,
of square miles in area, down to ones the size of
wedge-shaped, and various
houses (bergy bits) or cars (growlers). Tabular
irregular shapes, as shown here.
icebergs may rise to a height of up to 200 ft
(60 m) above the sea surface and extend underwater
to a depth of up to 1,000 ft (300 m). Most icebergs
appear white because of the light-reflecting
properties of air bubbles trapped in the ice.
Those made of dense, bubble-free ice absorb
all but the shortest (blue) light wavelengths
and so have a vivid blue tint. Occasionally,
icebergs roll over and expose a previously
submerged section to view, which appears
aqua green because of algae growing in the ice.
DOMED