Website design By BotEap.comThe extinction of the dinosaurs occurred during the end of the Cretaceous Period, about 65 million years ago, and caused the loss of up to 70 percent of all life on the planet. Although this event was not the only mass extinction in Earth’s history or the most severe, the extinction of the dinosaurs has spawned a variety of theories ranging from credible to less credible.

Website design By BotEap.comIce Age

Website design By BotEap.comIf an Ice Age had occurred during the Cretaceous Period, a considerable amount of the planet’s water and large areas of land would have been encased in ice. Since dinosaurs were thought to be cold-blooded, they probably would not have been able to cope with such extreme conditions and their numbers would have eventually dwindled.

Website design By BotEap.comDisease

Website design By BotEap.comThe disease is another suggestion for the extinction of the dinosaurs. However, it is difficult to see how a disease can be so prevalent as to wipe out large swaths of the animal population, travel great distances, and kill both terrestrial and marine species and plant life.

Website design By BotEap.comClimate change

Website design By BotEap.comIf there were a gradual change in Earth’s climate with a colder, drier environment and adapting plant life, dinosaurs might not have been able to adapt quickly enough to survive. Fossil records of dinosaur skulls show that they could only have had small brains. This indicates that the dinosaurs relied on automatic bodily responses rather than the cognitive decision-making responses that warm-blooded animals are known to make. So it might have been difficult for the dinosaurs to adapt to a changing environment and they may not have been able to compete effectively with warm-blooded animals.

Website design By BotEap.comSupernova

Website design By BotEap.comA supernova is a star that explodes with enough energy to keep our sun lit for six billion years. If Earth were hit by radiation resulting from a nearby supernova, it would have destroyed all life on the dinosaurs. There is no evidence that a supernova caused the extinction of the dinosaurs, and it is difficult to see how anything would have survived such an event.

Website design By BotEap.comThe volcano theory

Website design By BotEap.comVolcanic activity is known to have been widespread during the Cretaceous and is a credible reason why dinosaurs became extinct. The Deccan traps in western India and the Pacific basin areas are likely sites of higher volcanic activity at this time.

Website design By BotEap.comThe consequences of large-scale volcanic activity would have led to a nuclear-type winter with ash and gases added to the atmosphere, depleting sunlight and creating difficult conditions for dinosaur species. Hydrochloric acid, in particular, would have degraded the ozone layer allowing harmful ultraviolet rays to penetrate the surface.

Website design By BotEap.comThe high level of volcanic activity would also have emitted large volumes of greenhouse gases such as C02 and methane, increasing the Earth’s temperature and drastically changing the planet’s climate. The effects on the dinosaurs would have been catastrophic as they struggled to acclimate to the changing conditions, and the large-scale extinction of dinosaur species would have been inevitable.

Website design By BotEap.comCretaceous sediments support the theory of volcanic activity, as they contain higher than normal concentrations of minerals and sodium, both associated with volcanoes. Cretaceous sediments can also contain volcanic rock.

Website design By BotEap.comThe asteroid theory

Website design By BotEap.comIn the late 1970s, Luis and Walter Alvarez and scientists at the University of California were studying rocks from the KT boundary (or Cretaceous-Tertiary boundary) in Gubbio, Italy. Within the clay layer of the KT boundary they discovered iridium concentrations thirty times higher than normal. The two natural sources of this rare element are asteroids and lava from the Earth’s core, leading Luis and Walter Álvarez’s team to first suggest that an asteroid collided with Earth and caused the extinction of the dinosaurs. Álvarez’s team estimated that the asteroid would need to be ten kilometers in diameter to contain enough iridium to cause the iridium concentrations in the clay layer.

Website design By BotEap.comMore evidence has emerged to support an asteroid impact. The KT boundary has two layers. The top layer is three millimeters thick and includes soot that is believed to have come from global fires caused by the impact.

Website design By BotEap.comThe lower level is two millimeters thick and contains ejections from the asteroid’s impact site. This includes quartz crystals known as shock crystals that have been physically altered by high temperatures and intense pressure. The layer also contains tektites and micro tektites, which are often made of molten glass. The impacted crystals and tektites are closely associated with asteroid impact sites.

Website design By BotEap.comIn 1990, scientist Alan Hildebrand, after studying data collected by geophysicists looking for oil, noticed a ring structure called Chicxulub on Mexico’s Yucatán Peninsula. Chicxulub is a 180-kilometer-diameter crater and dates back to about 65 million years ago, at the same time as the extinction of the dinosaurs. A ten kilometer diameter object impacting the site was estimated to have caused the crater, which fits Alvarez’s team’s calculations for the size of the asteroid to create the KT boundary findings.

Website design By BotEap.comThe effects of an asteroid impact on dinosaurs

Website design By BotEap.comIt is estimated that the speed of the asteroid would have been about 100,000 kilometers per hour and the initial impact would have destroyed everything within a radius of 500 kilometers. The intense shock wave that followed would have caused large-scale fires, while trillions of tons of debris, gas and water vapor would have been thrown into the atmosphere.

Website design By BotEap.comEarthquakes, tidal waves, volcanic eruptions and strong winds would have followed. Soot and debris in the atmosphere would have blocked the sun for months, leading to fluctuating temperatures and a severe disruption of photosynthesis. Global fires would have emitted large volumes of CO2, increasing global temperatures and causing a chain reaction that would create sulfur dioxide that would fall in the form of acid rain.

Website design By BotEap.comThe fires would have destroyed up to 25 percent of all vegetation, and with photosynthesis unable to function effectively, the plant-eating dinosaurs would have starved to death. This, in turn, would have led to the large-scale death of carnivores, driving dinosaurs to extinction. Smaller animals, such as scavengers and birds, which could have traveled longer distances in search of food, would have been more likely to survive.

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Website design By BotEap.comOxygen levels in the sea would have decreased as deep sea water was carried to the surface by huge underwater currents. The plankton would have died as a result of a collapse of the food chain and widespread death. Acid rain may also have increased the acidity of the sea, killing vulnerable species.

Website design By BotEap.comProblems with the asteroid theory

Website design By BotEap.comWhile the impact of an asteroid has gained ground over most other theories, there are still problems with the theory. Paleontologists have yet to find dinosaur fossils dating back to the time of the impact, and some evidence suggests that the dinosaurs were already extinct prior to this event. In fact, dinosaurs had been in constant decline for tens of thousands of years before the Chicxulub asteroid struck.

Website design By BotEap.comThere have been a series of mass extinction events in Earth’s history and a series of large asteroid impacts. However, these impacts have never been the cause of mass extinctions. Some climate-sensitive species, such as frogs, are also known to have survived the Cretaceous extinction event, calling into question the asteroid’s true long-term effects on the environment.

Website design By BotEap.comDespite these problems with the asteroid theory, it remains the strongest explanation for the extinction of the dinosaurs. Perhaps the answer is not found in an explanation of the extinction of the dinosaurs, but in a combination of factors such as the impact of the asteroid at a time of increased volcanic activity. In the final analysis, perhaps the extinction of the dinosaurs was a case of accumulation of poorly synchronized events that very few species could cope with.