Selective Reading Guide Sample
Before you begin reading the passage, read the title
and all the headings in bold face. What do you think you will learn
about icebergs in this passage?
Icebergs
Read this paragraph
closely to find out how icebergs are born. Skim the second paragraph quickly.
Icebergs are a product of the fateful meeting of glacier and
sea. Today massive continental glaciers cover much of Greenland in the Northern
Hemisphere, and Antarctica in the south. Smaller glaciers extend to the edges
of Siberia and Canada's Northwest Territories. These ice fields produce giant frozen rivers that empty into the sea, where they
form shelves or tongues of glacial ice.
An iceberg is born, or calved, when tides and waves jostle the glacial shelf from
beneath and break off a large mass of ice,
which then floats out to sea.
The ice contained in a
typical berg is 5,000 years old. This substantial age reflects the duration of
the ice's journey from the glacier's
snowfield to the ocean. Most icebergs melt within two years at sea. The Arctic
and the Antarctic produce icebergs with distinctive sizes, shapes, and
movements.
After reading this paragraph, be sure you can tell
why Greenland produces so many glaciers. Underline the part that answers this
question.
The world's fastest-flowing glaciers meet the sea along the
west coast of Greenland. This region yields
about two-thirds of the 10,000 to 15,000 Arctic bergs calved every year.
Greenland's Jakobshavn Glacier alone produces some 1,350 per year. Greenland's
Petterman Glacier, one of the Northern Hemisphere's largest, has an ice shelf that extends as far as 25 miles (40
kilometers) into the ocean and produces unusually large, flat-topped ice islands.
See
if you can use the context of this paragraph to figure out what jostling means.
Icebergs accumulate in the inlets into which a glacier
flows. When the inlet becomes full, the noise of the bumping and jostling
icebergs can be heard for miles. Then, in great heaps, they spill out into the
ocean.
Quickly
read these sections on size, shapes and speed of icebergs. Complete the outline
below.
The icebergs of the Arctic do not approach the size of
Antarctica's. The largest confirmed Arctic iceberg was some 7 miles (11
kilometers) long and 3.7 miles (5.9 kilometers) wide. The visible portion of a
typical berg is less than 400 feet (120 meters) long and no more than 20 feet
(6 meters) high. But this represents only a fraction of its bulk, because the
mass beneath the surface is typically three to four times as great.
What Arctic icebergs lack in size they make up for in
fanciful, irregular shapes such as mounds, pinnacles, and wings. A
double-winged, or saddle, shape occurs when water erodes the berg around its
middle, while the ends rock in and out of the water.
Speed
Wings and pinnacles make excellent natural sails. A steady wind can greatly increase the speed of a
winged or pinnacled berg, and influence its direction as well. Once set in
motion, the iceberg continues to move forward on its own momentum until long
after the wind has subsided.
Movement.
Read these
paragraphs to answer the questions below
Where are the most dangerous icebergs formed?
About how far south can Arctic icebergs travel?
About how far south can Arctic icebergs travel?
The bergs from western Greenland are the most likely to
reach active shipping lanes. Some 800 to 1,000 of them reach the open ocean
each year and are swept southward by the powerful Labrador Current. More than
350 of these travel past Newfoundland into the busy seaways of the North
Atlantic.
Few icebergs survive farther south than 40 degrees north
latitude, because they quickly melt once they leave Arctic waters. The largest
can drift down along the eastern coast of North America to be caught up by the
Gulf Stream. Its warm waters quickly melt all but the very largest bergs. A few
last long enough to reach Bermuda, or to come within 100 miles (160 kilometers)
of Great Britain.
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