The impact sent 500 billion tons of debris into the atmosphere. Glow-
ing hot bits of crater debris flying past and back through the atmosphere set
ablaze global-wide forest fires upon landing. The raging inferno burned per-
haps one-quarter of all vegetation on the continents, turning a large part of
Earth into a smoldering cinder.A heavy blanket of dust and soot encircled the
entire globe and lingered for months, cooling the planet and halting photo-
synthesis.The planet was plunged into environmental calamity.
A catastrophe on this scale would have destroyed most terrestrial habi-
tats and caused extinctions of tragic proportions. Generally, no animal heavier
than 50 pounds survived the extinction. A large body size appears to have
been a severe disadvantage among terrestrial animals. Species living in the
tropics that relied on steady warmth and sunshine, such as the coral reef com-
munities, were especially hard hit. For example, the rudists, which built
reeflike structures, completely died out along with half of all bivalve genera.
A massive bombardment of meteorites might also have stripped away the
upper atmospheric ozone layer, bathing Earth in the Sun’s deadly ultraviolet
rays.The increased radiation would have killed land plants and animals as well
as primary producers in the surface waters of the ocean.The mammals, which
were no larger than rodents, coexisted with the dinosaurs for more than 100
million years. However, because they were mostly nocturnal and remained in
their underground borrows in the daylight hours, coming out only at night to
feed,the mammals would have been spared from the onslaught of ultraviolet
radiation during the daytime.
In the aftermath of the bombardment, Earth would have succumbed to
a year of darkness under a thick brown smog of nitrogen oxide. Surface waters,
poisoned by trace metals leached from the soil and rock, and global rains as
corrosive as battery acid would have dealt a deadly blow to terrestrial life-
forms. Plants that survived as seeds and roots would have been relatively
unscathed.The high acidity levels would have dissolved the calcium carbon-
ate shells of marine organisms, while those with silica shells would have sur-
vived as they have done during other crises. Land animals living in burrows
would have been well protected. Creatures living in lakes buffered against the
acid would have survived the meteorite impact quite well.
The impact could also have caused widespread extinctions of micro-
scopic marine plants called calcareous nannoplankton, which produce a
sulfur compound that aids in cloud formation. With the death of these
creatures, cloud cover would have decreased dramatically, triggering a
global heat wave extreme enough to kill off the dinosaurs and most marine
species. This contention is supported by the fossil record. It shows that
ocean temperatures rose 5 to 10 degrees Celcius for tens of thousands of
years beyond the end of the Cretaceous. During this time, over a period of
almost half a million years, more than 90 percent of the calcareous nanno-Historical Geology