Dennis Smith
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Smith is the author of 14 books. His latest is “San Francisco is Burning – The Untold Story of the 1906 Earthquake and Fires"
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OP-ED CONTRIBUTOR
When Nature's Wrath Is History's Reminder
by DENNIS SMITH NYTimes December 28, 2004
SCIENTISTS, like art teachers who have not mastered anatomy or drawing,
often assume that what they do not know is not important. And, when it
comes to earth science, what they do not know is the pattern of geologic
time, particularly what has happened beneath the ground in the 4.5
billion years that we assume the earth has existed. What have been the
consequences of large waves and water movement to whatever life existed
on its surface?
Humans might know that the universe is theorized to be 15 billion years
old, or that the Milky Way was formed 13 billion years ago, but the way
we feel about ourselves in relation to a 4.5 billion-year-old earth is
not much different from the way indigenous people studying a night sky
might have felt about themselves anywhere on earth 10,000 years ago. The
subject of what can possibly happen on earth is simply too big for most
of us to handle if we are to continue to be an optimistic race. And so
we hope for the best.
Yet there are some things we should be thinking about in a more serious
manner. There are facts that we should not let pass into an obscure
scientific history, for remembering them will undoubtedly help ensure a
safer future for all on our planet. This is harder than it sounds.
We have a tsunami warning system in the Pacific Ocean because, in recent
history, we've experienced tsunamis there. We don't have a similar
system in the Indian Ocean. This has something to do with the
technologies developing nations can afford, of course, But it also has
to do with the fact that our experience with the giant waves in this
region is less immediate. Yet the single worst explosion in our known
geologic history - an eruption of a 20-by-60-mile caldera some 71,000
years ago - occurred on Sumatra, just 100 miles from the epicenter of
Sunday's earthquake.
The earlier eruption left a 10,000 square-mile sheet of volcanic rock,
more than a thousand feet thick, and so filled the sky with ash that it
probably created our last ice age. Still, the eastern Indian Ocean is
thought to be an area of infrequent tsunami activity. Earthquakes as a
rule occur at the ridge of land and water, where plates usually meet and
either slide, thrust or pull apart, releasing awesome power. But there
are exceptions.
Americans believe that earthquakes are a West Coast problem. But the
largest earthquake ever in the United States that we know of, probably
at least as large as the one that destroyed most of San Francisco in
1906, occurred in the area of the Mississippi Valley in 1811. Boats were
thrown over in the river and people drowned. Whole islands simply
disappeared. This earthquake, and its aftershocks a year later, were so
destructive that Congress passed the first federal relief act in 1815 to
support the farmers whose previously healthy and farmable land was
turned to swamp, sand and mud.
The quake covered a much larger area than the San Francisco catastrophe,
but fewer people were killed, for in 1811 the area was sparsely settled
by fewer than 10,000, most living in log houses that would have
sustained the shaking well. However, the seismological activity that
caused it has never been explained in definitive terms.
Scientists speculate that the earth here tried but failed to separate
600 million years ago, creating a weakness of some kind beneath the
ground. The United States Geologic Survey vaguely refers to the area as a
plate boundary zone, which simply means that the agency doesn't know if
there are plate boundaries in the vicinity. But we do have historical
evidence of many substantial earthquakes in a wide area of the southern
Midwest, from St. Louis to Memphis - an area where more than 10 million
people live today.
The greatest cliché in geology is the question, Can it happen again?
Sure. Will it happen again? Well, nature is never overdue, and we simply
don't know. The earth has had many configurations of land, water and
living inhabitants over the ages, and if we think of an earth-changing
event as being "overdue," we are failing to understand geologic time. It
is mind-boggling to think that only 200 million years ago the earth was
one gigantic continent, and one can only imagine the explosions that
broke it into today's continents. The plates beneath these continents
continue to creep, and they don't need an earthquake to move them along.
We know that Baja California is moving away from Mexico at the rate of
two inches a year - and that it has been doing so for four to six
million years. We know that Europe is moving away from the United States
at the rate of one inch every year, and that Maui is moving away from
South America at the rate of three inches a year. Geodesy is the science
of the shape of the earth and, with the advent in the last decade of
global positioning systems, the geodesists in future will be able to map
every movement of the land and sea with authority and exactitude.
Our observation and reporting periods cover far too brief a period of
time to allow us to see any pattern. What's more, there are physical
realities in our world that we are not paying attention to. For
instance, in 1971 an earthquake of 6.4 magnitude occurred in the San
Fernando Valley in California. It occurred on a fault that had not been
known to exist, and so surprised scientists, as well as the 80,000
people who lived there.
At one end of this valley is the Van Norman Dam, which lost 30 feet from
its top, and tons of water, during the shaking. Behind it is a
reservoir larger than the one that created the famous Johnstown, Pa.,
flood that killed 2,200 people in 1889. Given the damage, cracks and
weaknesses that resulted, engineers concluded that the dam would have
collapsed altogether had the quake lasted another eight seconds. Today,
almost half a million people live in the valley.
Sunday's tragic earthquake occurred miles beneath the Indian Ocean, and
despite its 9.0 magnitude it was hardly felt in Indonesia, and not at
all in Sri Lanka. Yet the water displacement caused by the thrusting of
the Indian plate beneath the Burma plate created 30-foot waves that were
to kill people on the African coast more than 3,000 miles away. This
distance may seem hard to believe, but after the Great Chilean
Earthquake of 1960, tsunamis traveled more than 6,200 miles to Hilo,
Hawaii, where they killed 61 people and destroyed many buildings with
waves of more than 35 feet.
Oddly, a tsunami cannot be felt as it passes ships on the open ocean,
for the wave is usually small, one to two feet, and traveling very fast,
as fast as airliners. It is only as it approaches shallow water that it
begins to break; as the bottom of the wave slows, the top keeps
traveling at the higher speed and increases in height, hitting landfall
at 30 to 40 miles an hour. In 1958, an earthquake in Lituya Bay, Alaska,
caused a landslide into the ocean that created a tsunami 1,720 feet
high, a wave that could have swept over the Empire State Building.
Fortunately it headed into a wilderness area and did not travel across
the ocean to Hawaii or Japan.
The possibility of great landmasses falling into the ocean is always
with us, and recently scientists found vertical fault lines through a
volcano on La Palma, one of the smaller and more westward Canary
Islands. The volcano has a crater about five miles wide and a half-mile
high, and erupts about every 200 years. The last eruption was in 1948,
but the newly discovered fault lines have convinced some scientists that
eventually the huge crater will break apart and slide into the ocean,
bringing more than a half-trillion tons of rock with it.
Since tsunamis are created in proportion to the amount of land that has
fallen into the water, this event would likely create a wave mass never
before known to written history, many times bigger than the wave at
Lituya Bay. The wave would diminish a little as it crossed the Atlantic,
but if it hit the Atlantic Seaboard it could be higher than the
skyscrapers of Boston, New York, Washington and Miami. Scientists do not
know if it will take one, four, or 10 eruptions to separate the
landmass, only that the separation is inevitable.
The only good news is that volcanoes usually send signals before they
erupt, and it would take eight hours for the wave to travel from Africa
to the United States' eastern shoreline. It is not sufficient time,
however, to move all the people who would be in its path. In any event,
surely the mountain on La Palma should be reduced in size, to lessen the
impact should it ever slide into Atlantic. But, who will pay for such a
huge reduction of a landmass?
BIG earthquakes occur infrequently, but when they do they usually come
unexpectedly and with horrendous power. It is, of course, dangerous to
live in an earthquake-prone area, but what area in the world can we say
is earthquake-safe? Surely the people in the Mississippi Valley feel
they are safe, as do the people in New York City. Yet, New York has a
fault line going across 125th Street that I would guess 99 percent of
the city's population does not know about.
And even if they did, they would likely be no more concerned about it
than they are about La Palma. Americans have always lived in dangerous
places - on the flat cyclone fields of the Midwest, on the hurricane
battered coasts of Florida, on the flood plains of the South. We live in
these places because we are uncertain about the time and place of the
next disaster, and we are an adventurous culture. We believe that
lightning never strikes twice in the same place, despite the many times
it has.
I hope for the future in the same way I hope when I step on to an
airplane. I hope the people in control are of sound mind and body, and
that they know what they are doing. Yet I know that simply wishing this
is not enough. Each of us have to be responsible for our society's
future safety. Terrible events in the future are inevitable. Our first
responders, the best trained in the world, are prepared to meet any
challenge head-on, and have been responsible for saving many lives in
past crises. But I also know that as a society we will continue to be
unprepared for these crises if we don't look more deeply into the past.
By this, I don't mean a fire last year or a volcanic eruption a century
ago. I mean another past, in geologic time, that we simply don't know
enough about. Thinking about that explosion on Sumatra 71,000 years ago
is a good place to start.
Dennis Smith, a retired New York City firefighter, is the author of the
forthcoming "San Francisco Is Burning," a history of the 1906
earthquake.
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