Geoscience Reference
In-Depth Information
enough to level trees for miles around. The K-T impact event
released an amount of energy millions of times greater than these
relative pip-squeaks. The resulting shock wave leveled everything
standing within thousands of kilometers of ground zero, providing
fuel for the subsequent fires.
Sixty-five million years ago, the Yucatan Peninsula was an area of
shallow sea, so that the meteorite probably landed in less than 100 m
of seawater. Modeling indicates that the resulting earthquake caused
submarine landslides that displaced huge volumes of seawater and
generated a tidal wave that dwarfed even the most devastating in
human history. Traveling outward at about 0.5 km/sec, like the rip-
ples from a stone hurled by a giant, this ancient tsunami rose to a
height of 100 m and rolled inexorably across the oceans. Hardly
slowing as it went ashore, it traveled inland for 20 km, inundating
the coastal plains on half the globe.
As the meteorite penetrated deeper into the earth, a huge shock
wave converted it and the rock underneath into vapor and ejected
them outward at ballistic velocities. Some 100 km
3
of excavated
rock and 10
1
4
tons of vaporized comet or asteroid rose to altitudes
as high as 100 km. Much of this debris quickly fell back to earth, but
10 percent to 20 percent of it remained at high altitudes for months.
The temperature at ground zero rose to hundreds of thousands of
degrees, causing everything within a radius of several hundred kilo-
meters to burst into flame. The expanding fireball rose quickly and
within only a few hours had distributed itself around the earth.
Meanwhile, the shock wave had excavated a crater 15 km to 20 km
deep and at least 170 km in diameter. The impact generated an
earthquake of magnitude 12 to 13, a temblor at least 1,000 times
larger than any humans have ever experienced. Even 1,000 km from
ground zero, the earth's surface heaved in waves hundreds of meters
high.
A few minutes later, the mixture of vaporized meteorite and
rock, still traveling at ballistic velocities of 5 km/sec to 10 km/sec,
began to reenter the atmosphere. The individual globules were trav-
eling so fast that they ignited, producing a literal rain of fire. Over the
entire globe, successively later the greater the distance from the tar-
get, the lower atmosphere burst into a wall of flame, igniting every-
thing below. The effect was like "a domestic oven set at 'broil'."
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3
Everything that could burn did.
Smoke and soot rose to mingle with the huge number of fine
particles that the explosion had carried into the stratosphere. To-
gether they darkened the earth enough to cause the average global
