| 3001/
Permafrost forms when the mean annual temperature is approximately
27° F (-3° C).
3002/ Have you ever seen
a ring around the moon? Folklore has it that this means bad
weather is coming.
3003/ Within the solar
halo ring, on either side of the sun, one often sees two bright
spots called "sun dogs" or "mock suns".
Sun dogs and related phenomena are multicolored because they
are caused by refraction of the light through the ice crystals.
Refraction breaks sunlight up into the colors of the rainbow.
Sun dogs and halos always are at an angle of 22° from
the sun. That particular angle, curiously enough, occurs because
the refracting ice crystals have hexagonal (six-sided) faces.
3004/ If we consider
the earth as a whole, we find that the area covered by present-day
ice sheets is over one-third that covered during the greatest
extension of the last North American glaciation. The total
volume of ice is harder to estimate, but the rates of maximum
volume to present volume is probably around 3:1.
3005/ In 1936 a landslide
into Leon Lake, Norway, created a splash wave 230 feet high,
and at Cape Lopatka on the Kamchatka Peninsula, a tsunami
wave 210 feet high broke on the coast in 1737.
3006/ Alaska has more
than thirty known hot springs discharging water with temperatures
in excess of 40 C (104 F).
3007/ Major rivers such
as the Colorado and the Yellowstone together carry about 20
million acre-feet of water annually (an acre-foot is one acre
covered by one foot of water).
3008/ In temperate climates,
precipitation tends to percolate into the ground rather than
to run off in open stream flow. Less than 20 percent of precipitation
falling on the watershed of the Mississippi River actually
flows down Ole Man River.
3009/ Measurements of
abrasion to a marble block fixed underneath a moving glacier
in Iceland showed that 30 feet (10 meters) of ice motion cut
away about one-eighth inch (3 mm) of the block. At that rate,
the sliding of a debris-laden glacier would probably cut away
a yard (1 meter) of rock in about 200 years.
3010/ Avolume of water
starting at near 100°C (the boiling point) will totally
freeze in 90% of the time taken by an equal volume at about
room temperature.
3011/ During the last
million years, there have been at least four, and perhaps
as many as ten periodic invasions of ice around the world.
The last of these, known as the Great Ice Age, began about
70,000 years ago, peaked at about 20,000 years ago, and ended
8,000 years ago when the glaciers shrunk to approximately
their present-day limits.
3012/ Tsunamis have several
remarkable features. In the open sea where the water is deep,
they travel at speeds averaging about 450 miles per hour,
but they would not be discernible because the wavelength is
very long (usually over 100 miles) and the amplitude is very
low (a foot or two).
3013/ Oceanographers
studying old sedimentary rocks conclude that the basic composition
of the ocean hasn't changed over the past 700 million years.
3014/ The most common
type of halo is caused by light passing through a shower of
very small crystals which float in space with random orientations.
These form a ring around the sun (or moon) at a distance of
22 degrees from the light source.
3015/ If the growth rings
of a living bristlecone pine can be overlapped with dead pines
even older, a complete weather chronology extending as far
back as 8,000 years can be obtained.
3016/ The Yukon is the
United States third longest river; at 1,980 official miles
from its source in the Nisutlin River of the Yukon Territory
to its mouth in the Bering Sea, it is outstretched only by
the Missouri (2,540 miles) and the Mississippi (2,350 miles).
3017/ Siberia's Lake
Baikal at 1637 meters (nearly 5400 feet), it is the deepest
lake on the planet. The lake holds 1550 species or variants
of animals and 1085 of plants; of these, 1000 occur nowhere
else.
3018/ Scientifically
minded people have been puzzling over why snowflakes have
six sides for a long time. Way back in 1611, the famous astronomer
Johannes Kepler took time off from peering at the heavens
to write an essay "On the six-cornered snowflake."
3019/ When it first freezes,
an ice floe is only about half as salty as the sea water in
which it forms. Over the course of one winter, the ice will
lose half to two-thirds of its initial salt burden.
3020/ Because the bottom
of a waxed ski and the surface of ski trails are both grainy,
a surprisingly small percentage of ski base is ever in contact
with snow on an established trail. In dry snow at 15 degrees,
for example, researchers found that only one percent of the
ski-base area was in contact with the snow surface. Skiing
over freshly-fallen snow is a different story. In fresh snow,
or in snow close to the melting point, about 80 percent of
the ski base is in contact with the trail because water forces
much of the air out of the snow pack.
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