Why extinct dinosaurs

Strong evidence suggests that a huge asteroid impact caused the mass dinosaur extinction 66 million years ago. During Beta testing articles may only be saved for seven days. Create a list of articles to read later. You will be able to access your list from any article in Discover.

The end of the Cretaceous Period saw one of the most dramatic mass extinctions Earth has ever seen. Find out what brought about the end of the dinosaurs and many other animals too. The fossil record shows that for the first million years of their existence, dinosaurs took on a huge variety of forms as the environment changed and new species evolved that were suited to these new conditions. Dinosaurs that failed to adapt went extinct. But then 66 million years ago, over a relatively short time, dinosaurs disappeared completely except for birds.

Many other animals also died out, including pterosaurs, large marine reptiles, and ammonites. Other scientists think it unlikely that any dinosaur could have had a rapid metabolic rate. Some scientists think that very big Did people and dinosaurs live at the same time? After the dinosaurs died out, nearly 65 million years passed before people appeared on Earth.

However, small mammals including shrew-sized primates were alive at the time of the dinosaurs. Many scientists who study dinosaurs vertebrate paleontologists now think that birds are direct descendants of one line of carnivorous dinosaurs, and Did all the dinosaurs live together, and at the same time?

Dinosaur communities were separated by both time and geography. Different dinosaur species lived during each of these three periods. For example, the Jurassic dinosaur Stegosaurus had already been extinct Do any mass extinctions correlate with magnetic reversals? There is no evidence of a correlation between mass extinctions and magnetic pole reversals. Can USGS photos of fossils be downloaded or viewed online? Fossil photos can also be viewed as published plates within many online USGS publications.

The best keywords for searches are author names, such as William Cobban, Norm Filter Total Items: Year Published: Divisions of geologic time Bookmark DescriptionThis bookmark presents information that is widely sought by educators and students.

View Citation. Geological Survey, , Divisions of geologic time ver. Year Published: Why Study Paleoclimate? Why Study Paleoclimate? Year Published: Divisions of Geologic Time—Major Chronostratigraphic and Geochronologic Units Effective communication in the geosciences requires consistent uses of stratigraphic nomenclature, especially divisions of geologic time.

Geological Survey Geologic Names Committee. Year Published: A tapestry of time and terrain Vigil, J. A tapestry of time and terrain; ; I; ; Vigil, J. Year Published: Geologic age: using radioactive decay to determine geologic age At the close of the 18th century, the haze of fantasy and mysticism that tended to obscure the true nature of the Earth was being swept away.

Geologic Survey. Year Published: Mud fossils At the close of the 18th century, the haze of fantasy and mysticism that tended to obscure the true nature of the Earth was being swept away. In , Russian astronomer Joseph Shklovsky became the first scientist to consider the extinction was due to a single catastrophic event when he theorized that a supernova the explosion of a dying star showered the earth in radiation that could have killed the dinosaurs. Once again, the problem with the theory was explaining why dinosaurs died out and other species did not.

Also, scientists said that such an event would have left evidence on the surface of the earth—trace amounts of radiation dating back to the Cretaceous Period. None was found. Enter Luis Alvarez, a Nobel Prize-winning physicist, inventor and pioneer in the field of radiation and nuclear research. He and his son, noted geologist Walter Alvarez, were conducting research in Italy when they discovered a centimeter-thick layer of iridium-enriched clay at the K-T boundary. Iridium is rare on earth, but more common in space.

The Alvarezes published their findings in , postulating that the thin layer of iridium was deposited following the impact of a large meteor, comet or asteroid with the earth. At the time, the Alvarez theory was so far removed from prevailing hypotheses that it was ridiculed. Slowly, though, other scientists began finding iridium evidence at various places around the globe that corroborated the Alvarez theory. There was, however, no smoking gun in the form of an impact site.

The Chicxulub Crater, as it was dubbed, was named for a nearby village. Scientists believe the bolide that formed it was roughly 6 miles in diameter, struck the earth at 40, miles per hour and released 2 million times more energy than the most powerful nuclear bomb ever detonated. Miles-high tsunamis would have washed over the continents, drowning many forms of life. Shock waves would have triggered earthquakes and volcanic eruptions. The resulting darkness could have lasted for months, possibly years.

Many dinosaurs would have died within weeks. The carnivores who feasted on the herbivores would have died a month or two later. Save Back. Grades 3—5 , 6—8. Some Leading Theories A big meteorite crashed into Earth, changing the climatic conditions so dramatically that dinosaurs could not survive.

Ash and gas spewing from volcanoes suffocated many of the dinosaurs. Diseases wiped out entire populations of dinosaurs. Food chain imbalances lead to the starvation of the dinosaurs. View not found. Download the PDF from here.