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OTHER EXTINCTION THEORIES

Did changes in Earths environment lead to dinosaur extinction?

Although the predominate dinosaur extinction theory is that an asteroid impact dramatically changed Earths climate, there are some paleontologists who think otherwise. These scientists believe that changes in Earths environment played a much more important role in the extinction of life forms on Earth and that the impact 65 million years ago just killed off the remaining species.

Once very common in the worlds oceans, ammonites suffered a huge die-off and eventually became extinct around the time of the Chicxulub impact (iStock).

Recent studies of the fossil record have examined changes in a wide range of plant and animal species populations toward the end of the Cretaceous period. Only single-celled marine life showed a sudden decline at the end of this period. Other species declined gradually, with a few groups showing no change. And there was no evidence for a catastrophic mass extinction in the fossil record.

Instead, the majority of extinctions may have occurred gradually due to environmental changes such as falling sea levels and volcanic eruptions. The sea level apparently dropped by approximately 328 feet (100 meters) during this time. Also, debris from volcanic eruptions in India may have been thrown into the atmosphere. Both could have contributed to a gradual extinction of many flora and fauna species.

What is a problem with the environmental theory of dinosaur extinction?

The main problem with the environmental theory of dinosaur and other life form extinctions lies in the conflicting evidence in the fossil record. For example, evidence for the environmental theory includes ammonite (hard-shelled relatives of squid) fossil records. One record shows they were in decline for approximately 11 million years before finally going extinct, but other fossil evidence indicates the impact at Chicxulub suddenly killed off from one-half to three-quarters of ammonite species along the coasts of France and Spain.

Unfortunately, the fossil record of Cretaceous dinosaurs is very limited for the last 10 million years of that period. In fact, the only good dinosaur records from this time are in western North America and this evidence is limited to the last two million years of the Cretaceous period. Thus, this poor, discontinuous dinosaur fossil record may be the real cause for the apparent reduction in their diversity, and not environmental causes.

What are killer cosmic clouds?

Killer cosmic clouds are large areas in outer space, probably bigger than our entire solar system, that have much higher concentrations of hydrogen than normal. For the past five million years, our planet has been traveling in a relatively empty, typical region of space, with a density of less than one particle (mostly hydrogen) per cubic inch. Killer clouds are found where new stars are being formed and have much higher densities of hydrogen on the order of hundreds of particles per cubic inch.

Some scientists believe that a killer cloud could collapse the solar systems heliosphere a bubble of space produced by the solar wind that partially protects our planet (and the other planets and satellites in our solar system) from cosmic rays. Cosmic rays are high-speed particles from outer space that constantly hit the heliosphere, but most are deflected by this shield. This is good because exposure to the powerful radiation from these rays could fry a human being. If the heliosphere around our planet collapsed from the introduction of a cosmic cloud, much higher levels of cosmic radiation would strike Earth, dramatically altering life, though scientists are not sure how much or in what ways.

Could a killer cosmic cloud have caused the extinction of the dinosaurs?

If supercomputer models are correct, then higher concentrations of hydrogen could have formed a wall and caused the heliosphere around Earth to collapse. This could have allowed more cosmic radiation to penetrate to Earths surface, resulting in changes to the flora and fauna. If this did occur, such an increase in cosmic rays, with elevated levels of radiation, could have directly killed the dinosaurs. Another scenario is that the rays negatively affected the vegetation eaten by the herbivorous dinosaurs and other animals. As carnivorous dinosaurs no longer had any prey, they also would have died off.

Is there any proof that Earth has encountered a cosmic cloud In the past?

No, there is no proof of encountering a cosmic cloud. Some scientists believe that, from time to time, our planet could have encountered smaller, less dense clouds of hydrogen, known as the Local Fluff. These less-devastating encounters, according to the models, would have only weakened the heliosphere, with slight increases in cosmic rays hitting Earth.

One of the known side effects of cosmic rays striking Earth is the production of the rare metal beryllium. An increase of this metal could be proof that we had encountered one of these relatively benign clouds. Ice cores taken from the South Pole do indeed show an increase in beryllium levels at approximately 35,000 and 60,000 years ago, leading scientists to speculate that contacts were made with Local Fluff. What are the effects of these minor encounters? Scientists speculate that the effect of Earth coming into contact with the Local Fluff might have produced anything from an ice age to an increased greenhouse effect.

What is the true story of dinosaur extinction?

Many scientists believe that dinosaurs became extinct not due to one reason, but rather from a combination of reasons, most of which are examined above. In addition, some scientists believe that dinosaurs were already gradually declining when catastrophe occurred 65 million years ago. There is a chance that they would have become extinct anyway with or without a catastrophe happening.

Could a killer cosmic cloud have caused the mass extinction on Earth 65 million years ago? The high concentration of hydrogen in space clouds like this one may have temporarily collapsed Earths heliosphere, according to one theory (NASA).

 
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