How did the dinosaurs died? This questions has been asked to the scientist since the first evidence of dinosaurs was discovered. But, nobody could give a valid answer so far. In 21st century, we have some new reasons to believe that meteors coming from outer space killed all the dinosaurs. In this article, we will discuss this matter in light of the researches done by the scientists.
Evidence for the Event
There are now many lines of evidence to prove that a relatively large impact happened 65 Million years ago.
- The iridium excess in the 65 Million years-old soil layer has been confirmed at many points around the world.
- The same soil layer contains grains of quartz that were deformed by high shock pressures, as would occur in a giant explosion. (The deformation is a microscopic structure called “twinning,” in the crystals).
- The same soil layer contains enough soot to correspond to burnding down all of the forests of the world. This suggests that massive fires were touched off at the time of impact.
- The same soil layer, especially around the Gulf of Mexico, contains massive deposits of tumbled boulders, as would be generated in a large tsunami, or “tidal wave.” The geographic distribution of tsunami deposits suggest the impact was in the Caribbean area.
- After a decade of searching, scientists in 1990 identified the crater associated with this material. It is no longer visible on the surface of the Earth, but is buried under sediments. It straddles the coast of Yucatan. It is revealed by mapping the strength of the gravity field over that area, and by drilling; it has been dated to 65 Million years old.
- Astronomers have charted numerous asteroids that cross Earth’s orbit. From studies of orbit statistics, it is estimated that asteroids of 10 km size can hit the earth roughly every 100 Million years or so — which fits with the idea that we actually did get hit 65 Million years ago by an object this size. (Smaller hits are much more common).
What Happened during the Event?
Asteroids hit Earth typically at high speeds of 16 to 32 km/sec (10-20 miles/sec). During the impact, the kinetic energy in the asteroid (or energy of motion) is converted to explosive energy, blowing debris of dust, soil, and rocks not only into the atmosphere, but out into space, where it fell back into the top of the atmosphere. Early calculations in the 1980s (using in part ideas worked out by Carl Sagan and his colleagues) showed that so much dust entered the high atmosphere that the Earth was shrouded in a dust layer that blocked sunlight for several weeks or months. This would have killed some plants, disrupting the food chain.