how is radioactive and absolute dating related?

While relative time allows scientists tell the story about Earth’s events, it does not give specific numerical ages and, therefore, cannot provide information on the speed at which geologic processes are operating. Based on Hutton’s principle of uniformitarianism (see Chapter 1), early geologists surmised geological processes work slowly and the Earth is very old. The use of relative dating principles allowed scientists to understand Earth history up until the late 19th century. Radioactivity was discovered in late 1800s and scientists were able to use it as a scientific tool. This new technology allowed them to give specific units of time, such as years, to minerals within rocks. Absolute dating is a method that does not depend on the comparisons to other rocks. Radioisotopic dating, the most popular type of absolute dating, is discussed here. [2]

SHRIMP, or Sensitive High Resolution Ion MicroProbe, was invented at Australian National University Canberra’s Research School of Earth Sciences in the early 1980s. It revolutionized age dating with the U-Pb system. The SHRIMP allows for the identification of specific areas of growth in single grains of zircon and baddeleyite. Accurately dated In some cases it may be less than 100 000 year. The technique dates not only older mineral cores, which we refer to as inherited cores but also magmatic or metamorphic overgrowths. This allows it to unravel the geological history for a single grain of mineral. This technique can also date nonradioactive mineral grains that contain zircons or monazite inclusions, like in the sapphire grain. SHRIMP technology is now being exported to the USA, France and Russia. When there are enough accessories zircon grains, it can fix the maximum age for sedimentary rocks (which usually requires about 100 grains). This was a great reminder from Asiah Flores, Kaifeng (China) which we truly thank. [3]

Elaina sweet at evolution-outreach.biomedcentral.com, trace amounts of isotopes of radioactive elements, including carbon-14, uranium-238, and dozens of others, are all around us—in rocks, in water, and in the air (Table 1). These isotopes are unstable, so they gradually break apart or “decay.” Radiometric dating Because radioactive elements decompose in predictable ways, just like a clock’s ticking. Here’s how it works. You can have one collection. Million atoms of a radioactive isotope, half of them will decay over a span of time called the “half life.” Uranium-238, for example, has a half life of 4.468 billion years, so if you start with a million atoms and come back in 4.468 billion years, you’ll find only about 500,000 atoms of uranium-238 remaining. Rest of the uranium is likely to have decomposed to about 500,000 other elements and eventually to nonradioactive atoms like lead-206. If you wait another 4.468 trillion years, only 250,000 atoms will be left (Fig. 8). Modified by Terry Rodriguez, Vijayawada (India) on April 14, 2020 [4]