Credit & Copyright: courtesy V.L. Sharpton,
LPI
Explanation:
What killed the dinosaurs?
Their sudden disappearance 65 million years ago,
along with about 70 percent of all species then living on Earth, is
known as
the K-T event (Cretaceous-Tertiary Mass Extinction event).
Geologists and paleontologists often
entertain the idea that a large
asteroid or comet impacting the Earth was the culprit.
In such a cosmic catastrophe, the good(!) news would be that
the impact would generate
firestorms, tidal waves, earthquakes, and hurricane winds.
As for the bad news ...
debris thrown into the atmosphere would have a serious global environmental
consequences, creating extended periods of darkness,
low temperatures, and acid rains - resulting in a planet-wide
extinction event.
In 1990, dramatic support for this theory came
from cosmochemist Alan Hildebrand's
revelation of a 65 million year old, 112 mile wide ring structure
still detectable under layers of sediment in the Yucatan Peninsula
region of Mexico.
The outlines of the structure, called
the Chicxulub crater
(named for a local village), are visible in
the above representation of gravity and magnetic field
data from the region.
In addition to having the right age, the crater is consistent with
the impact of an asteroid of sufficient
size (6 to 12 miles wide) to cause the global disruptions.
Regardless of the true cause of the K-T event, it is fortunate that
such impacts are
presently believed
to happen only about once every 100 million years!
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NASA Official: Jay Norris. Specific rights apply.
A service of: LHEA at NASA / GSFC
& Michigan Tech. U.
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Публикации с ключевыми словами:
Earth - dinosaur - K-T event - impact - crater - астероидная опасность - астероиды
Публикации со словами: Earth - dinosaur - K-T event - impact - crater - астероидная опасность - астероиды | |
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