On human and natural disasters
By Frederic Friedel
On Sunday, December 26, 2004 at 7:58:53 a.m. local time the fourth largest
earthquake in the world since 1900 occurred off the west coast of northern
Sumatra. The resulting tsunami caused more casualties than any other in recorded
history, killing more than a quarter of a million people.
Some time after the disaster had struck we published a
report on it, not least because many of our readers requested we do so,
despite the absence of a direct chess link. Since then we have received a steady
stream of letters on the subject, and today we return to the subject in a more
scientific vein.
One early letter which stood out was from John Nunn, mathematician, grandmaster,
chess publisher, who is very knowledgeable on any subject connected with science
in general. John wrote:
"I think this whole Indian Ocean Tsunami disaster demonstrates
how badly people assess risks involving rare but catastrophic events. There
is a consistent error in such assessments: risks involving human agencies
are regularly over-estimated, while risks involving natural agencies are
regularly under-estimated. Thus the following risks are over-estimated:
- Terrorism
- Nuclear power stations
- Genetically modified food
The following risks are under-estimated
- Volcanic eruptions
- Earthquakes
- Asteroid impacts
- Epidemics
It is depressing to consider the vast amounts spent on anti-terrorism
measures (including the Iraq war), many of them quite pointless, while a
few million dollars would have provided a tsunami warning system which would
probably have saved a huge number of lives."
This letter struck a note (and drove us to write this article). For some years
I myself have been posing the following question to friends and associates:
Which of the following events should we be most afraid of:
- International terrorism and the personal threat to us or our community.
- A nuclear mega-accident, resulting from atomic weapons or catastrophic
failure of a nuclear power station.
- Genetically modified life-forms escaping from laboratories and causing widespread
death and debilitation.
- Catastrophic climate change brought about by excessive levels of CO2 emitted
into the atmosphere.
- The Yellowstone National Park.
After a while I usually pass out a "hint": one of the above disasters
is infinitely more devastating and capable of killing orders of magnitude more
people than the other four. It is also very much more likely to occur. And
finally there is, in the foreseeable future, absolutely nothing we can do about
it. We will come back to the subject below.
2004 MN4
Will the world as we know it end on Garry Kasparov's 66th birthday? This question
is not as flippant as it looks. In fact for a few days at the end of last year
it looked like a very distinct possibility that an asteroid could impact Earth
on that day. According to NASA it would strike with an energy of about 1400
megatons of TNT, 25 times more than the largest thermo-nuclear bomb ever tested
and about 100 times more powerful than the Tunguska explosion over Siberia
in 1908.
Hard to see: 2004 MN4 in a telescope image |
2004 MN4 is the unimaginative name given to a large rock –
or small asteroid – that is moving in Earth-crossing orbit. It is estimated
to be 400 meters (1300 feet) in length and to have a mass of around one million
metric tons. 2004 MN4 was discovered in June 2004 by astronomers
at the Kitt Peak National Observatory in Arizona. They observed it for two
nights. The object was rediscovered on December 18 in Australia, after which
first calculations of a possible Earth impact could be made.
On December
24 NASA published an impact chance figure of "around 1 in 62"
(or 1.6%), the highest probability for any asteroid ever observed. In the course
of a week NASA corrected the estimate on the basis of more observations to
1 in 37 or 2.7%.
Subsequently the asteroid was precovered (discovered on older photographs).
In addition, NASA has just finished conducting radar measurements with the
Arecibo radio telescope in Puerto Rico. The result of the new calculations
is a zero percent chance of Earth impact. 2004 MN4 will pass the
earth at a distance of 36,350 km (or 22,600 miles), which is closer to the
planet than geosynchronous satellites that relay TV and communication signals.
The flyby will occur on April 13, 2029, which coincidentally is a Friday (paraskavedekatriaphobes
can find relief here)
and, even more ominously, Garry Kasparov's 66th birthday! [When we told him
about NASA's latest findings Garry expressed relief: "Thank heavens. You
know that people would have blamed it on me!"]
On April 13 2029 the rock will be easily visible to the naked eye, having
a magnitude of 3.3. You will be able to see it at around 11 p.m. in Europe,
moving past the constellation of Gemini moving at a rate of 42° per hour,
which is less than half as fast as the International Space Station moves across
the sky.
It should be noted that all impact estimates rely on a complete knowledge
of the inner solar system and all the interactions that 2004 MN4
will have from now until the year 2029. Unfortunately our knowledge of the
inner solar system is far from complete, and even a tiny change in the path
of the rock, due for instance to an encounter with an unknown object will produce
a substantial variation in the final earth-crossing position.
Currently there are 671 known asteroids with earth-crossing orbits. These
are being tracked by NASA's Near Earth
Object Program. None is considered potentially hazardous to earth in the
near future.
Risk assessment
In the follow-up to the original fairly dire risk calculations published by
NASA, John Nunn retracted "asteroid impacts" from his list of humanity-threatening
natural disasters. "Thinking about it a bit more, I don't think there
is much danger from an asteroid impact. I had thought about the 1908 Tunguska
impact, equivalent to perhaps a 10-megaton hydrogen bomb. Assuming one impact
a century, this sounds quite dangerous. But if you assume that the impact kills
everyone in an area of a thousand square kilometres, then, with surface area
of Earth = 500 million square kilometres, that would be about 12 people per
square km. Thus the impact kills 12,000 people or 120 per year. Thus it isn't
much of a danger at all, compared for instance to epidemics, which are far
more of a danger than the others."
A web page entitled "The
Odds of Dying" (have a few hours free if you go here) gives precise
figures: the lifetime odds for dying of heart disease is 1 in 5, of cancer
1:7, stroke 1:23, car accidents 1:100, firearms 1:325, air travel 1:20,000,
lightning 1:83,000, earthquake 1:132,000, asteroid impact 1:200,000 and Tsunamis
1:500,000.
The devastating Indian Ocean Tsunami of December 26, 2004, has caused well
over 250,000 deaths. But how does it compare to other natural disasters in
recent history? Here are a few statistics:
2003: An earthquake in Bam, Iran, officially killed 26,271
1976: An earthquake in Tangshan, China, killed 242,000
1970: A cyclone in Bangladesh killed 500,000
1923: The Tokyo earthquake killed 140,000
1887: China's Yellow River broke its banks in Huayan Kou killing 900,000
1826: A tsunami killed 27,000 in Japan
1815: A volcanic eruption of Mount Tambora on Indonesia's Sumbawa Island killed
90,000
1556: An earthquake in China's Shanxi and Henan provinces killed 830,000
Mega Tsunamis
Let us return to Tsunamis. Devastating as the December 26 tidal wave was,
it pales to insignificance compared to some of the geological time-bombs that
are slumbering around the globe. These can release mega-tsunamis, more destructive
than anything we have witnessed in mankind's history. And the next episode
is likely to emanate from the balmy Canary Islands off the coast of North Africa,
causing a wall of water to cross the Atlantic Ocean with the speed of a jet
airliner and devastate the East Coast of the United States.
Mega-tsunamis are generally landslide-generated. The greatest danger comes
from large volcanic islands which are prone to massive landslides. For instance
the sea floor around Hawaii is covered with the remains of truly colossal landslides
that occurred millions of years ago. Fortunately, such events are very rare,
but concern is growing that ideal conditions for such a landslide currently
exist – on the island of La Palma in the Canaries. During a 1949 eruption
of the southern volcano, Cumbre Vieja, a gigantic fissure appeared across the
side of the volcano, and the western half slipped a few metres towards the
Atlantic before stopping in its tracks.
Schematic by the Universidad de Barcelona
Scientists believe that the western flank of the volcano might give way completely
during a future eruption, causing a mass of around 500 thousand million tonnes
to slide into the Atlantic Ocean. This would generate an almost inconceivably
destructive wave, which would surge across the entire Atlantic in a few hours.
The worst case scenario envisages an initial bulge of water 900 meters high.
This subsides to form waves in excess of 100 m in height that strike neighbouring
islands. After an hour waves 50 to 100 m high hit the Northwest African coast.
Spain and the UK experience waves 7 to 10 m high, two to five hours after the
collapse. After nine hours, the Florida coastline can expect to face around
a dozen waves between 20 and 25 m high. It would engulf the East Coast of the
US, sweeping away everything up to a distance of 20 km inland.
Yellowstone
Which brings us back to our little quiz at the top of this page: which disaster
should we fear most? The correct answer, as many of you might have suspected,
was Yellowstone National Park. It turns out that this famous tourist attraction,
visited by millions each year, is a so-called "super-volcano", one
thats eruption would be unlike anything we have ever witnessed – at
least in the last 75,000 years.
Super-volcanoes are created when magma creates a giant reservoir in the Earth's
crust. This increases to an enormous size, building up colossal pressure until
it finally erupts. This happens on a "mega-colossal" scale (scientists
classify volcanic explosions as gentle, explosive, severe, cataclysmic, paroxysmal,
colossal, super-colossal and mega-colossal). The explosion would cover the
North American continent with many inches of ash and debris, bringing all life
to a standstill. And it would send ash, dust, and sulphur dioxide into the
atmosphere, which would circle the Earth, darkening the skies for a number
of years, causing temperatures to plummet. Many species of animals and plants
would face extinction. The last time a super-volcano blew, Toba 74,000 years
ago in Sumatra, it reduced the population on Earth to just a few thousand people.
Mankind was pushed to the edge of extinction.
The good news is that Yellowstone has a fairly stable eruption cycle of 600,000
years. The bad news: the last eruption was 640,000 years ago.
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