Download 1 SECTION VI. Extinction [one plasma monitor, runs 4.5 minutes

American Museum of Natural History – Dinosaurs: Ancient Fossils, New Discoveries
da_ExtinctionAtTheKT_SCRIPT_v47 - Script
SECTION VI. Extinction [one plasma monitor, runs 4.5 minutes)
Scientists:
Denton Ebel
AMNH Ph: 212/769-5381; E-mail: [email protected]
Gerta Keller
Dept of Geosciences 308 Guyot Hall, Princeton
University, Princeton, NJ 08544.
Ph: 609/258-4117; E-mail: [email protected]
__________________________________________________________________
NARRATOR: One of the most puzzling questions about nonavian dinosaurs isn’t
about how they lived. It’s about how they died.
ON-SCREEN TITLE: Extinction at the K-T
ON-SCREEN INTER-TITLE: IMPACT
NARRATOR: There is no doubt that a meteorite—either an asteroid or comet—
collided with Earth 65 million years ago.
Denton Ebel: We know, from modeling of nuclear explosions and other physical
models of the atmosphere, that an impact of this size would cause massive,
massive devastation. Tidal waves, huge winds and hurricanes, dust that would
block out the sun. The vapor would go high up into space and rain down on
Earth as fine, condensed dust, depositing a layer, iridium-rich, all across the
globe.
Iridium is found at the K-T boundary all over the world in a thin layer. Iridium
is not abundant in crustal rocks or volcanic rocks, but it is abundant in
meteorites.
ON-SCREEN INTER-TITLE: VOLCANISM
NARRATOR: There is also evidence that massive volcanic eruptions occurred
around this same time. The Deccan Traps is an immense volcanic plateau, over
a mile thick in places, that covers much of western India. Its formation, over
the course of hundreds of thousands of years, may have been as destructive as
a sudden impact.
Beginning around 66 million years ago, molten magma from deep inside Earth
erupted to the surface, creating an active fissure hundreds of miles long. The
massive volcanism unleashed huge concentrations of gases into the
atmosphere.
Gerta Keller: I study mass extinctions and their causes, and in particular, I look
for evidence of meteor impacts and volcanism and how it affects life on Earth.
I use foraminifera for such studies.
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American Museum of Natural History – Dinosaurs: Ancient Fossils, New Discoveries
da_ExtinctionAtTheKT_SCRIPT_v47 - Script
Fossilized foraminifera, or forams, are tiny microorganisms. I use forams
because they contain information about environmental changes in their shells.
Because there are tens of thousands of forams in a single piece of rock like
this, this can tell us a lot about the environment in which the dinosaurs and the
forams lived.
NARRATOR: Many species of forams declined and eventually became extinct
soon after the Deccan Traps eruptions began. Such evidence suggests that the
Deccan Traps volcanism altered global temperatures, causing major ecological
changes around the globe for hundreds of thousands of years.
ON-SCREEN INTER-TITLE: SEA LEVELS
NARRATOR: Climate change over an even longer period of time also may have
played a role. 100 million years ago, inland seas flooded Earth’s continents.
Over the course of millions of years, these shallow inland seas gradually
retreated to the lower ocean basins.
Scientists theorize that without the temperature regulating effect of inland
seas, climate across the globe became more extreme with hotter summers and
colder winters.
Many species declined over the last 10 million years of the Cretaceous.
NARRATOR: From existing evidence, we know that at the end of their reign,
dinosaurs faced long-term climate changes, intense volcanic activity and,
finally, a massive extraterrestrial impact.
All three profoundly would have affected life on Earth. And while most
scientists agree that the impact played a major role in the K-T extinction, they
continue to investigate the effects of volcanism and long-term climate change.
As we continue to gather information and study clues from 65 million years
ago, we come closer to revealing the complex picture of life—and death—at the
K-T boundary.
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