One half-life is the time it takes for ½ of the parent isotopes present in a rock or bone or shell to decay to daughter isotopes.
Parent isotopes decay to daughter isotopes at a steady, exponential rate that is constant for each pair.
For humans, the steady movement of the hands on a clock marks off the seconds and the hours.
In nature, the constant decay of radioactive isotopes records the march of years.
The original unstable isotope is called the parent isotope, and the more stable form is called the daughter isotope.
Isotopes decay at an exponential rate that that can be described in terms of half-life.
To make sure they didn't get a bogus date, the research team developed a special protocol that involved washing the coral with hydrogen peroxide and then only selecting the purest samples."When we cut off a centimetre-long sample, we'd crush it and process it and look at it under high magnification and only pick out those very small pieces that were pristine, that hadn't been affected by any erosion processes," Prof Weisler said.During excavations at Nukuleka, Dr Burley found numerous fingers of acropora coral, which had been used by Lapita people as files and rasps."They'd break living coral fingers off the reef and use these for abrading shell and wood for shaping and forming these raw materials into various tools and artefacts," Prof Weisler said.The researchers dated the coral using a method known as uranium/thorium dating, often used to study long-term changes in climate.People known as Lapita were previously estimated to have arrived in Tonga sometime around 3,000 years ago."We have done a lot of archaeology on this people that we refer to as the Lapita peoples and it is defined by a very distinctive type of ceramics with complex motifs," lead author Dr David Burley, a professor of Archaeology at Simon Fraser University in Canada, told Radio Australia's Pacific Beat program."And this type of ceramic occurs first in the Bismarck archipelago off the New Guinea coast and then it proceeds east and we can track it all the way across the Pacific to Tonga, which is the end of the line for this kind of pottery."The pottery was subjected to radiocarbon dating which gave an arrival date within of 178-year window between 2,769 and 2,947 years ago.Prof Weisler proposed using another dating method to get a more precise date on first settlement.You are a marine scientist studying the deep-sea corals growing on a seamount.In order to understand coral life and history, you need to know something about the age and growth patterns of these organisms. As a coral animal grows, it secretes a hard external skeleton.With the advent of legislation in the mid-1960s designed to protect archaeological sites in the United States threatened by increased urban development or government sponsored projects, archaeological surveys and excavations were mandated as a means for preserving information otherwise destroyed.As a result, thousands of projects have contributed to a growing body of “gray literature,” To send this article to your Kindle, first ensure [email protected] added to your Approved Personal Document E-mail List under your Personal Document Settings on the Manage Your Content and Devices page of your Amazon account. Note you can select to send to either the @free.or @variations.Radioactive isotopes absorbed from seawater by the animal are incorporated into the skeleton, where they begin to undergo radioactive decay.Radiometric dating will reveal the age of individual corals on the seamount.