For about half of the 20th century both scientists and the general public regarded dinosaurs as slow, unintelligent cold-blooded animals. However, the bulk of research since the 1970s has supported the view that they were active animals with elevated metabolisms, and often with adaptations for social interactions. This change of view was strongly influenced by evidence of the descent of birds from theropod dinosaurs.Since the first dinosaur fossils were recognized in the early nineteenth century, mounted dinosaur skeletons have become major attractions at museums around the world. Dinosaurs have become a part of world culture and remain consistently popular among children and adults. They have been featured in best-selling books and films (notably Jurassic Park), and new discoveries are regularly covered by the medi.
In colloquial English "dinosaur" is sometimes used to describe an obsolete or unsuccessful thing or person, despite the dinosaurs' 160M-year reign and the global abundance and diversity of their descendants, the birds. This usage became common while dinosaurs were regarded as cold-blooded and sluggish. Non-avian dinosaurs suddenly became extinct approximately 65 million years ago.
In colloquial English "dinosaur" is sometimes used to describe an obsolete or unsuccessful thing or person, despite the dinosaurs' 160M-year reign and the global abundance and diversity of their descendants, the birds. This usage became common while dinosaurs were regarded as cold-blooded and sluggish. Non-avian dinosaurs suddenly became extinct approximately 65 million years ago.
There are many theories about why the dinosaurs finally became extinct, some of which are more than a little outlandish. The two main 'serious' theories are the asteroid/meteor and volcano theories.
Barringer Meteor Crater in northern Arizona is a bowl-shaped depression 180m deep and 1.2km in diameter. It was named after American scientist Daniel M. Barringer who in 1905 theorized that the crater was meteoric in origin. The crater was the first impact site of an object to be identified on the Earth. Scientists think that the crater was formed sometime between 25,000 and 50,000 years ago by an iron meteorite, somewhere between 30 and 100m in diameter, weighing roughly 60,000 tons.
The energy released by the impact was roughly equivalent to 3.5 million tons of TNT. Most of the object vaporized, but about 30 tons of fragments have been collected. There are other craters on the planet but due to erosion and plate movement it takes a trained eye to find them. From these two examples it can be seen that when large objects enter the atmosphere a great deal of energy can be released causing large amounts of damage. This evidence helps to support the Asteroid theory.
Barringer Meteor Crater in northern Arizona is a bowl-shaped depression 180m deep and 1.2km in diameter. It was named after American scientist Daniel M. Barringer who in 1905 theorized that the crater was meteoric in origin. The crater was the first impact site of an object to be identified on the Earth. Scientists think that the crater was formed sometime between 25,000 and 50,000 years ago by an iron meteorite, somewhere between 30 and 100m in diameter, weighing roughly 60,000 tons.
The energy released by the impact was roughly equivalent to 3.5 million tons of TNT. Most of the object vaporized, but about 30 tons of fragments have been collected. There are other craters on the planet but due to erosion and plate movement it takes a trained eye to find them. From these two examples it can be seen that when large objects enter the atmosphere a great deal of energy can be released causing large amounts of damage. This evidence helps to support the Asteroid theory.
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