Why did the Dinosaurs disappear?

Luis Alvarez, who came up with the ‘evidence’ for the collision of an asteroid
65 million years ago, which killed off the dinosaurs, has been disproved. Why
is it that people still present it as fact ?

Alvarez discovered layers of rock known to be 65 million years old and he found
that one layer contained unusually high amounts of iridium. Iridium is 100 000
times more abundant in asteroids. We all know the story of the dust-cloud
killing off the dinosaurs. But the point is, the fossils give no record of
this. Many plants and animals did become extinct at the time of the dinosaurs,
but the disappearance was gradual over millions of years. Furthermore they
disappear at different times in different places. But the iridium layer? The
research, carried out by Robert Reynolds and Michael Rampino, shows it has
been misinterpreted. Volcanic eruptions produce iridium also. The Alvarez
layer in Italy, is of the same composition of the layers above and below it.
This is just as you would expect if the iridium layer had been produced
locally, but it contradicted the idea that the iridium had settled out of the
atmosphere all over the earth at one time, after an asteroid collision. If
volcanoes produced the iridium then there should be quite a few layers in the
rocks of that period. This is exactly what the Italian team found. In the
rocks of the Alvarez site six other such layers were found. The Alvarez team
reported that it had looked for other layers, but found none. Apparently, it
did not look hard enough.

In 1983, geologists dealt another blow. Deep-sea cores, extracted by
drilling, contain sediments from over millions of years. Every 500,000 years
the eart’s magnetic field flips, or changes direction. Scientists measured the
pattern of the magnetic field recorded in rock from New Mexico, that was rich
in dinosaur bones. Next they matched their data to the patterns in the Alvarez
site. The conclusion: The dinosaur bones do not disappear when the iridium
layer appears; instead they continue on well into the next magnetic zone. With
this result, the connection between the dinosaurs and the asteroid disappeared.
So there we are. The asteroid theory was very attractive because it explained
so much in a simple way , and many people will regret it’s passing. However
the evidence against it is strong.