The Permian—Triassic extinction event , also known as the P—Tr extinction ,  the P—T extinction ,  the End-Permian Extinction ,  and colloquially as the Great Dying ,  formed the boundary between the Permian and Triassic geologic periods , as well as between the Paleozoic and Mesozoic eras, approximately There is evidence for one to three distinct pulses, or phases, of extinction. The speed of the recovery from the extinction is disputed. Previously, it was thought that rock sequences spanning the Permian—Triassic boundary were too few and contained too many gaps for scientists to reliably determine its details.
How Do Scientists Determine the Age of Dinosaur Bones? | HowStuffWorks
This is how carbon dating works: Carbon is a naturally abundant element found in the atmosphere, in the earth, in the oceans, and in every living creature. C is by far the most common isotope, while only about one in a trillion carbon atoms is C C is produced in the upper atmosphere when nitrogen N is altered through the effects of cosmic radiation bombardment a proton is displaced by a neutron effectively changing the nitrogen atom into a carbon isotope. The new isotope is called "radiocarbon" because it is radioactive, though it is not dangerous.
Working out how old archaeological remains are is a vital part of archaeology. Scientific dating has confirmed the long residence of Aboriginal people in Australia. A number of methods are used, all of which have their advantages, limitations and level of accuracy.
A technician of the U. Geological Survey uses a mass spectrometer to determine the proportions of neodymium isotopes contained in a sample of igneous rock. Cloth wrappings from a mummified bull Samples taken from a pyramid in Dashur, Egypt. This date agrees with the age of the pyramid as estimated from historical records. Charcoal Sample, recovered from bed of ash near Crater Lake, Oregon, is from a tree burned in the violent eruption of Mount Mazama which created Crater Lake.