Meteor
Impact
Arizona
In 1984, the paleontologists Raup and Sepkoski argued that there is a cyclical pattern to the extinction events recorded in the fossil record. The pattern implied a 26 million year cycle, itself indicative of an extra-terrestrial cause. There are no known terrestrial causes for such massive and regular extinctions. Could Planet X be to blame, perhaps through showering Earth with comets as it achieves perihelion?
The 26 million-year cycle would have to be a coincidental pattern, which is an unsatisfactory explanation scientifically.
Energy
Conservation
of
Momentum
Momentum
Tragedy
in the Carribean
K-T Event
Sixty-five million years ago about 70% of all species then living on Earth disappeared within a very short period. The disappearances included the last of the great dinosaurs. Paleontologists speculated and theorized for many years about what could have caused this "mass extinction," known, as the K-T event (Cretaceous-Tertiary Mass Extinction event). Then in 1980 Alvarez, Alvarez, Asaro, and Michel reported their discovery that the peculiar sedimentary clay layer that was laid down at the time of the extinction showed an enormous amount of the rare element iridium. First seen in the layer near Gubbio, Italy, the same enhancement was soon discovered to be world wide in that one particular 1-cm (0.4-in.) layer, both on land and at sea. The Alvarez team suggested that the enhancement was the product of a huge asteroid impact.
K-T Event
Sixty-five million years ago about 70% of all species then living on Earth disappeared within a very short period. The disappearances included the last of the great dinosaurs. Paleontologists speculated and theorized for many years about what could have caused this "mass extinction," known, as the K-T event (Cretaceous-Tertiary Mass Extinction event). Then in 1980 Alvarez, Alvarez, Asaro, and Michel reported their discovery that the peculiar sedimentary clay layer that was laid down at the time of the extinction showed an enormous amount of the rare element iridium. First seen in the layer near Gubbio, Italy, the same enhancement was soon discovered to be world wide in that one particular 1-cm (0.4-in.) layer, both on land and at sea. The Alvarez team suggested that the enhancement was the product of a huge asteroid impact.
Iridium
It is fortunate that more Iridium is in
Meteors than in the Earth. As the Meteor hits the Earth
the irdium is spread out.
Bryson says that they used a method called Nuclear
Activation. They aimed neutrons at the sample and
caused the stable Iridium
to become radioactive. The scientists counted the radiation
emanating from the sample and by calculating backwards
determined how much Iridium
was in the sample!
By taking the sample and pulverizing it, heating it and sending the particles through a
Mass Spectrometer they could count each element in the sample.
Comet
Shoemaker-Levy
A truly large
collision in the Solar System.
and
another
