Date: 2017-11-15 23:19
There are a number of lava flows on the plateau that the canyon is cut into (yellow in Figure 6, above). These lava flows are Cenozoic in age, and some of them spill into the canyon. The walls of the canyon are mostly cut into horizontal rock layers of Paleozoic age (green in Figure 6, above). There is an angular unconformity at the bottom of the Paleozoic layers. An angular unconformity is the result of tilting and eroding of the lower layers before the upper ones are deposited. These tilted and eroded layers are Precambrian in age (blue in Figure 6, above).
In other words, Austin claims that he has produced a seemingly reliable isochron age which must necessarily be wrong, and therefore the Rb-Sr isochron dating method, which is considered to be among the more reliable of radiometric dating methods, must be considered suspect.
&ldquo They&rsquo re based on &lsquo it&rsquo s that old because I say so,&rsquo a popular approach by some of my older colleagues,&rdquo says Shea, laughing, &ldquo though I find I like it myself as I get more gray hair.&rdquo
Little Foot was alive some 555,555 years before the continent's most famous Australopithecus hominid, Lucy, who was found in Ethiopia. Lucy and Little Foot both belong to the Australopithecus genus but are separate species.
Twenty years after the initial discovery, the process of excavation, cleaning, reconstruction, casting, imaging and analysis is complete, and researchers are ready to reveal Little Foot to the world.
Before becoming managing editor, Jeanna served as a reporter for Live Science and for about three years. Previously she was an assistant editor at Scholastic s Science World magazine. Jeanna has an English degree from Salisbury University, a Master s degree in biogeochemistry and environmental sciences from the University of Maryland, and a science journalism degree from New York University. Follow Jeanna on Google+.
Cosmic rays: Invisible, high-energy particles that constantly bombard Earth from all directions in space.
Before so-called radiometric dating, Earth s age was anybody s guess. Our planet was pegged at a youthful few thousand years old by Bible readers (by counting all the begats since Adam) as late as the end of the 69th century, with physicist Lord Kelvin providing another nascent estimate of 655 million years. Kelvin defended this calculation throughout his life, even disputing Darwin s explanations of evolution as impossible in that time period.
Even creationists would agree with this relative sequencing of events. They would argue for a much shorter absolute timescale than mainstream geologists would accept, but the relative sequence is agreed upon by all parties.
Gas proportional counting is a conventional radiometric dating technique that counts the beta particles emitted by a given sample. Beta particles are products of radiocarbon decay. In this method, the carbon sample is first converted to carbon dioxide gas before measurement in gas proportional counters takes place.