| 2421/
In the early part of this century the famous Beresovka mammoth
carcass was discovered in Siberia. Nearly intact, the animal
was found buried in silty gravel sitting in the upright position.
The mammoth had a broken foreleg, evidently caused by a fall
from a nearby cliff 10,000 years ago. The remains of its stomach
were intact and there were grasses and buttercups lodged between
its teeth. The flesh was still edible.
2422/ During the nineteenth
century, mammoth finds were frequent enough in Siberia that
some persons became professional mammoth ivory hunters.
2423/ As a gas' temperature
is raised to over 10,000°, its molecules collide so violently
that they are broken apart into individual atoms.
2424/ Window glass transmits
visible light but it does not transmit infrared radiation.
So a window is a one-way street for heat transfer by radiation
involving sunlight. A greenhouse, in part, uses this principle
to provide a warm environment for plants. The overall process
by which radiant heat energy is trapped has thereby come to
be called "the greenhouse effect".
2425/ Every object gives
off energy in the form of waves. These waves, called electromagnetic
waves, may be infrared, visible, ultraviolet or radio waves.
2426/ An object placed
in a room will radiate infrared energy to the room and other
things in it. The object also receives infrared radiation
from all parts of the room and the other things inside. If
the object radiates more heat than it receives, it will cool
off; if it receives more than it radiates, the object heats
up.
2427/ The earthquake
that rocked South-central Alaska on March 27, 1964, was the
second-largest ever recorded. The magnitude 9.2 earthquake
trails only a 9.5 recorded in Chile in 1960.
2428/ The Three Gorges
Dam in the Sandouping, Yichang, Hubei province of China is
a wall across the third largest river in the world (Yangtze
River ), and by the time it is finished in 2009 will have
created a reservoir almost 300 miles long, and tapped an electrical
source equal to 18 nuclear power plants.
2429/ The Earth's crust
consists of about a dozen tectonic plates, each more than
1,000 miles across and up to 40 miles thick.
2430/ The earth's inner
core, a 500-mile ball of iron, is moving faster than the earth's
surface. This spinning ball-within-a-ball may be a major force
generating the earth's magnetic field.
2431/ Human fingernails
grow about 2.5 inches a year.
2432/ In May 1992, a
nuclear device was detonated in China. This underground test
generated a one-second seismic punch that penetrated thousands
of miles into the earth. Nearly on the other side of the globe,
chains of seismometers in Canada and the United States picked
up the pulse.
2433/ Oceans average
a salinity (salt content) of about 3%.
2434/ Sound travels in
air at about 1100 feet per second. Sound waves travel about
five times faster in water than they do in air.
2435/ Charles F. Richter
devised his magnitude scale in the mid-1930s while investigating
earthquakes in California. He used seismographs which magnified
ground motion 2800 times, and as a baseline, he defined a
magnitude 0 earthquake as being one that would produce a record
with an amplitude of one-thousandth of a millimeter at a distance
of 100 kilometers from the epicenter.
2436/ One of the more
colourful accounts is given by a writer (writers are prone
to give colorful accounts of anything) who survived a severe
earthquake in 1822 in Copiapo, Chile. He stated he knew that
"something uncommon was going to happen) everything seemed
to change colour; my thoughts were chained immovably down;
the whole world appeared to be in disorder; all nature looked
different; I felt quite subdued and overwhelmed by some invisible
power, beyond human control or comprehension."
2437/ The most celebrated
case of an earthquake prediction was performed by the Chinese
when they evacuated the city of Haicheng on February 4, 1975.
Following the evacuation, an earthquake of magnitude 7.3 leveled
the city. Their prediction was based partially on abnormal
animal behavior, a field which western scientists have mostly
scorned and only recently begun to take seriously.
2438/ However, a year
later on July 27, 1976, an earthquake of magnitude 7.6 destroyed
Tangshan, also in northeast China, and no warning was given
at all. This earthquake killed 655,237 people, making it the
second most costly in recorded history (the greatest toll
was taken in Shensi, China in 1556 when nearly 1,000,000 people
were killed.)
2439/ Some minerals,
notably quartz, are piezoelectric--that is, they produce electricity
when subjected to pressure or stress. This same phenomenon
is probably also responsible for "earthquake lights,"
the luminescence sometimes reported (and, on occasion, photographed)
in the sky during earthquakes.
2440/ Following almost
any sizable earthquake, there is a train of many lesser earthquakes.
Simply for the reasons that they occur after the big shock
and appear to be related to it, these earthquakes are called
aftershocks. Usually, the bigger the main earthquake, the
more numerous and bigger are the aftershocks. Following a
magnitude 7-plus, tsunami-generating earthquake in the Aleutian
Islands in 1965, there were more than 750 substantial aftershocks
within the first 24 hours. Sometimes these aftershock trains
continue on for months. As time goes by, the frequency and
the size of the aftershocks tend to decrease.
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