Deadly quakes help
renew the planet
Shifting plates build mountains,
enrich soil But earthquakes,
eruptions extract a horrible price
WILLIAM J. BROAD
NEW YORK TIMES NEWS SERVICE
They approach the topic gingerly, wary of
sounding callous, aware that the geology
they admire has just caused a staggering
loss of life. Even so, scientists argue that in
the very long view, the global process
behind
great
earthquakes
is
quite
advantageous for life on Earth — especially
human life.
Powerful jolts like the one off Sumatra on
Dec. 26 that sent massive waves racing
across the Indian Ocean are the inevitable
side effects of the constant recycling of the
planetary crust, which produces a lush,
habitable planet. Some experts refer to the
regular blows — hundreds a day — as the
planet's heartbeat.
The advantages began billions of years ago,
when this crustal recycling made the oceans
and atmosphere and formed the continents.
Today, it builds mountains, enriches soils,
regulates
the
planet's
temperature,
concentrates gold and other rare metals,
and maintains the sea's chemical balance.
Plate tectonics (after the Greek word tekton,
or builder) describes the overall geology.
The tragic downside is that waves of
earthquakes and volcanic eruptions along
plate boundaries can devastate human
populations.
"It's hard to find something uplifting about
150,000 lives being lost," says Donald
DePaolo, a geochemist at the University of
California, Berkeley.
"But the type of geological process that
caused the earthquake and the tsunami is
an essential characteristic of the Earth. As
far as we know, it doesn't occur on any other
planetary body and has something very
directly to do with the fact that the Earth is a
habitable planet."
Many biologists believe that eons ago, the
process may have even given birth to life
itself.
Jan. 15, 2005. 01:00 AM
The main benefits of plate tectonics
accumulate slowly and globally over the
ages. In contrast, its local upheavals can
produce regional catastrophes, as the recent
Indian Ocean quake made clear.
Even so, scientists say, the Indian Ocean
tsunamis may prove to be an ecological
boon over the decades for coastal areas
hardest hit by the giant waves.
Jelle Zeilinga de Boer, a geologist at
Wesleyan University who grew up in
Indonesia and has studied the archipelago,
says historical evidence from earlier
tsunamis suggests that the huge waves can
distribute rich sediments from river systems
across coastal plains, making the soil richer.
"It brings fertile soils into the lowlands," he
says. "In time, a more fertile jungle will
develop."
De Boer, author of recent books on
earthquakes and volcanoes in human
history, adds that great suffering from
tectonic violence was usually followed by
great benefits as well.
"Nature is reborn with these kinds of terrible
events," he says. "There are a lot of positive
aspects even when we don't see them."
Plate tectonics holds that the Earth's surface
is made up of a dozen or so big crustal slabs
that float on a sea of melted rock. Over
ages, this churning sea moves the plates as
well as their superimposed continents and
ocean basins, tearing them apart and
rearranging them like pieces of a giant
jigsaw puzzle.
The process starts as volcanic gashes spew
hot rock that spreads out across the seabed.
Eventually, hundreds or thousands of
kilometres away, the cooling slab collides
with other plates and sinks beneath them,
plunging back into the hot earth.
The colliding plates grind past one another
about as fast as fingernails grow, and over
time produce mountains and swarms of
earthquakes as frictional stresses build and
release. Meanwhile, parts of the descending
plate melt and rise to form volcanoes on
land.
The recent cataclysm began in a similar
manner as volcanic gashes in the western
depths of the Indian Ocean belched molten
rock to form the India plate. Its collision with
the
Burma
plate
Deadly quakes help renew the planet
Page 2 of 2
created the volcanoes of Sumatra, as well
as thousands of earthquakes, including the
magnitude 9.0 killer.
But despite staggering losses of life, says
Robert Detrick Jr., a geophysicist at the
Woods Hole Oceanographic Institution in
Woods Hole, Mass., "there's no question
that plate tectonics rejuvenates the planet."
Moreover, geologists say, it demonstrates
the Earth's uniqueness. In the decades after
the discovery of plate tectonics, space
probes among the 70 or so planets and
moons that make up the solar system found
that the process existed only on Earth — as
revealed by its unique mountain ranges.
In the book Rare Earth, which explored the
likelihood that advanced civilizations dot the
cosmos, Peter Ward and Donald Brownlee
of the University of Washington argued in a
chapter on plate tectonics that the slow
recycling of planetary crust was uncommon
in the universe yet essential for the evolution
of complex life.
"It maintains not just habitability but high
habitability," said Ward, a paleontologist.
(Brownlee is an astronomer.) Most
geologists believe that the process yielded
the
Earth's
primordial
ocean
and
atmosphere, as volcanoes spewed vast
amounts of water vapour, nitrogen, carbon
dioxide and other gases. Plants eventually
added oxygen. Meanwhile, many biologists
say, the Earth's first organisms probably
arose in the deep sea, along the volcanic
gashes.
"On balance, it's possible that life on Earth
would not have originated without plate
tectonics, or the atmosphere, or the
oceans," says Frank Press, the lead author
of Understanding Earth and a past president
of the National Academy of Sciences.
The volcanoes of the recycling process
make rich soil ideal for growing coffee,
sugar, rubber, coconuts, palm oil, tobacco,
pepper, tea and cocoa. Water streaming
through gashes in the seabed concentrates
copper, silver, gold and other metals into
rich deposits that are often mined after plate
tectonics nudges them onto dry land.
Experts say the world's oceans pass
through the rocky pores of the tectonic
system once every million years or so,
increasing nutrients in the biosphere and
regulating a host of elements and
compounds, including boron and calcium.
William Schlesinger, dean of the Nicholas
School of the Environment and Earth
Sciences at Duke University, says one vital
cycle keeps adequate amounts of carbon
dioxide in the atmosphere.
"Having plate tectonics complete the cycle is
absolutely essential to maintaining stable
climate conditions on earth," Schlesinger
says.
"Otherwise, all the carbon dioxide would
disappear and the planet would turn into a
frozen ball."
1. What is the main point behind this
article?
2. What do scientist describe the
powerful jolts that occur as?
3. Describe the origins of the term
Plate Tectonics.
4. What are the advantages of quakes
in the past and today?
5. What are the disadvantages of
quakes?
6. What did scientist discover decades
after the discovery of plates?
7. Where do scientists believe the first
organisms came from?
8. What benefits do volcanoes play to
life on earth?