A mega-tsunami is simply a
gigantic wave, one big enough to cross oceans and destroy cities.
They can be thousands of feet high moving at supersonic speeds.
They can be caused by
huge meteors
crashing into the ocean, or by
massive landslides.
No boat or building hit by a mega tsunami could survive. But now
scientists believe that we could be sitting on a time bomb, that
sooner or later one will destroy New York, Boston and Miami, and
that nothing could stop it.
The largest tsunami in recorded history was in Lituya Bay,
Canada, 1958. An earthquake measuring 8.3 on the Richter scale
caused 40 million cubic metres of rock to fall into the sea. A wave
more than half a kilometre high was created that surged through the
bay devastating all in its path. This was not even a mega-tsunami,
by these standards it was tiny, but it did show scientists what
sort of wave a small landslide could cause. But what would be the
effect of a big one?
Scientists hunted that world for sites that could potentially
cause a mega tsunami. They discovered that at least eleven mega
tsunamis had happened in the last 200,000 years, caused by island
collapses in the Hawaiian and Canary islands.
The island of La Palma, in the Canary Islands off the coast of
North Africa, was discovered to be in great danger of collapsing.
The island is volcanic and during an eruption of the Cumbre Vieja
volcano in 1949 part of the island slipped a few metres into the
sea before stopping. Another eruption could cause the western flank
of the island to collapse in the Atlantic Ocean.
No one knows. It will happen during an eruption of Cumbre Vieja.
It is an active volcano, last erupting in 1949. However the next
eruption may not destroy the island, the next 10 may not. Only on
thing is certain - one-day an incredible force will surge through
the Atlantic Ocean.
It would be far bigger than any wave ever seen for thousands of
years. 500 billion tonnes of rock are waiting to collapse into the
ocean at terrific speed. The collapse would create nearly
5,000,000,000,000,000 (5 thousand trillion) joules of kinetic
energy, which would be converted into a colossal wave 900 metres
high with awesome speed - within ten minutes it would have moved
250 kilometres. The landslide would continue to move underwater,
powering the wave as it goes.
No coastline in the North Atlantic would be spared. Britain,
France, Spain and Portugal would all be badly hit North Africa
would be hit by 100 metre waves, but the main wave would travel
west. It would storm across the Atlantic in hours, hitting the
Caribbean and Brazil badly. However, the real damage would be to
the East coast of the USA.
By the time it had travelled the 4000 miles to America the wave
would be lower and wider. It would now be just 50 metres high but
many kilometres long, allowing it to sweep up to 20 miles in land,
destroying everything in its path. Boston, New York and Miami would
virtually be wiped off the map. Skyscrapers would be bulldozed as
if they weren't there. Bridges would be ripped from their
foundations. And virtually every human in these cities would be
killed.
There would be indirect consequences around the world. The events
of the 11 September wiped millions off stock markets around the
world. What would be the effects of the destruction of not only the
rest of New York, but also the rest of the East Coast on the
world's economies?
Put simply, we can't. We have no technology that can stop a
volcano erupting, no support that can hold 500 billion tonnes of
rock and no barrier that can stop a wave moving at 500 miles per
hour. All we can do is evacuate.
But can we evacuate tens of millions of people with just a few
hours notice? Unless evacuation plans were incredibly well thought
out, no. Imagine New York's grid locked streets trying to cope with
every person in the city on them. The alternative is evacuating
when the volcano starts to erupt, possibly giving a few weeks
warning. However, the island may not collapse on the next eruption,
or even the next ten. Would we risk evacuating millions of people
on the off chance? Could we risk not to?
