Geography Reference
In-Depth Information
One of the first people to make a case for the formation of the mountains from the bottom of the sea was
Leonardo da Vinci (1452-1519). A naturalist who viewed art as an attempt to understand nature, Leonardo
hiked through the mountains of Italy and wondered about the creation of the Alps. Observing the pres-
ence of fossil seashells, he naturally questioned how they could exist at the top of mountains. Conven-
tional medieval wisdom would have attributed these fossils to the biblical flood that covered the earth, but
Leonardo's observations weren't chained to a demanding faith in scripture. He wrote in his notebooks that
the surface of the earth was once covered by water, and the mountains of the earth had been uplifted from
the ocean floors. Over the years, rains stripped away parts of the mountain, leaving rocky crags. Writing
around five hundred years ago, his ideas about mountain building and erosion were uncannily close to the
truth as it is understood today.
These are the mountains we can see. There are taller mountains on earth but we don't see all of them
and tend to discount them. The volcanic Mauna Kea in Hawaii measures 33,476 feet high, taller than
Mount Everest. But only a small portion—13,680 feet—is visible above the surface of the ocean.
Geographic Voices
“Because it is there.”
George Leigh Mallory attempted to climb Mount Everest three times. During a tour of America
after his second attempt, Mallory was repeatedly asked, “Why do you want to climb Mount
Everest?”
His famous reply has become an all-purpose reason for daring to accomplish extraordinary
things. Mallory was killed making his third attempt in 1924.
Earthquakes: Who's at Fault?
It takes a fairly substantial earthquake to make headlines. When it happens on live television during the
middle of the World Series, as happened in the San Francisco-Oakland area in October 1989, it makes very
big headlines. According to the United States Geological Survey, there are several
million
earthquakes rat-
tling teacups around the world each year. Most of these are so small and occur in such remote areas that
they go undetected by the most sensitive of seismic instruments (from the Greek word for earthquake,
seis-
mos
,
seismic
means “caused by or related to earthquakes”).
Earthquakes are another result of plate movements. As the plates shift, rocks are either compressed or
stretched by their motions. As that happens, the rocks store energy, but the stresses are powerful. Like a
spring stretched too far or pressed down long enough, the pressure ultimately must be released. The rocks
snap and the tremendous energy stored inside of them is released as an earthquake. Earthquakes occur at
all three types of plate borders. At diverging plates, underwater earthquakes are relatively small. But col-
liding plates can produce huge shocks. In 1976, an enormous earthquake struck China, with a sudden surge
of the Australian plate the most likely cause. As the following list of major earthquakes shows, China has
been prone to such disasters for much of recorded history and the first attempts to study earthquakes were
made by the Chinese. The first recorded earthquake occurred there in 1831
BC
and after a quake in 1177
BC
, the Chinese began to keep regular records of quakes. An extraordinary Chinese scientist-astronomer
named Zhang Heng developed the first seismograph in
AD
132. When a tremor hit, a ball fell from the
mouth of a bronze dragon into the mouth of one of a series of bronze frogs below to indicate the direction
of the earthquake's origin.
Instead of having direct, head-on collisions, some plates are sliding uneasily past each other in a lateral
motion. The area between these two ships passing in the night are fault zones. In the United States, the
