The age of the Earth is estimated to be 4. Following the development of radiometric age-dating in the early 20th century, measurements of lead in uranium-rich minerals showed that some were in excess of a billion years old. It is hypothesised that the accretion of Earth began soon after the formation of the calcium-aluminium-rich inclusions and the meteorites. Because the time this accretion process took is not yet known, and predictions from different accretion models range from a few million up to about million years, the difference between the age of Earth and of the oldest rocks is difficult to determine. It is also difficult to determine the exact age of the oldest rocks on Earth, exposed at the surface, as they are aggregates of minerals of possibly different ages. Studies of strata - the layering of rocks and earth - gave naturalists an appreciation that Earth may have been through many changes during its existence.
How Do We Know the Earth Is 4.6 Billion Years Old?
How old is Earth? A word to sceptics on the dating game
Aristotle thought the earth had existed eternally. Roman poet Lucretius, intellectual heir to the Greek atomists, believed its formation must have been relatively recent, given that there were no records going back beyond the Trojan War. The Talmudic rabbis, Martin Luther and others used the biblical account to extrapolate back from known history and came up with rather similar estimates for when the earth came into being. Within decades observation began overtaking such thinking. In the s Nicolas Steno formulated our modern concepts of deposition of horizontal strata. He inferred that where the layers are not horizontal, they must have been tilted since their deposition and noted that different strata contain different kinds of fossil. This position came to be known as uniformitarianism, but within it we must distinguish between uniformity of natural law which nearly all of us would accept and the increasingly questionable assumptions of uniformity of process, uniformity of rate and uniformity of outcome.
Dating Rocks and Fossils Using Geologic Methods
This page has been archived and is no longer updated. Despite seeming like a relatively stable place, the Earth's surface has changed dramatically over the past 4. Mountains have been built and eroded, continents and oceans have moved great distances, and the Earth has fluctuated from being extremely cold and almost completely covered with ice to being very warm and ice-free. These changes typically occur so slowly that they are barely detectable over the span of a human life, yet even at this instant, the Earth's surface is moving and changing.
Geochronology is the science of determining the age of rocks , fossils , and sediments using signatures inherent in the rocks themselves. Absolute geochronology can be accomplished through radioactive isotopes , whereas relative geochronology is provided by tools such as palaeomagnetism and stable isotope ratios. By combining multiple geochronological and biostratigraphic indicators the precision of the recovered age can be improved. Geochronology is different in application from biostratigraphy, which is the science of assigning sedimentary rocks to a known geological period via describing, cataloging and comparing fossil floral and faunal assemblages.