Absolute Ages of Rocks

Absolute Age

Absolute Age means the numerical age, in the years, or a rock or object.

Isotopes

All atoms of a given element have the same numer or protons. For example, all hydrogen atoms have one proton, but an elements atoms can have different numbers of neutrons. The three different forms of hydrogen atoms are called hydrogen isotopes.

Atoms

An atom is the smallest part of an element that has all the properties of the element. Each atom contains smaller particles called protones, neutrons, and electorns. Protons and neutrons are in the atoms nucleus, electorns suround.

Half-Life

An isotopes half life is the time required for half of the parent isotopes to decay into daughter isotopes.

Isotopes

Isotopes are atoms of the same element that have different numbers of neutrons.

Radioactive Decay

Radioactive Decay is the process by which an unstable element naturally changes into another element that is stable.

Different Types of Isotopes

Radioactive Isotopes with short half-lives cannot be used for dating old rocks. Geologists often use a combination of radioactive isotopes to measure the age of rocks.

The Age of Earth

However, individual crystals of the mineral zircon in igneaus Australia have been dated at 4.4 billion years. Radio metric dating of rocks form the moon and meteorites indicate that Earth is is 4.54 billion years old. Radiometric dating, the relative order of the rock layers and fossils all help scientist understand Earth's long history.

Radiometric Ages

In this process called radiometer in dating scientists measure the amount of parent isotope and daughter isotope in a sample of the material they want to date. Form this ratio they ca determine the materials age. Scientists make these precise measurements in laboratories

Radioactive Decay

Most isotopes are stable which mean they don't change under normal conditions. Although some isotopes at unstable known as radioactive isotopes. Radioactive isotopes change or decay overtime. As they decay, they release energy and form new, stable atoms.

Dating Rocks

Radiocarbon dating is useful only for dating organic material—material from once living organisms. In most Fossils, living tissue had been replaced by rover, forming minerals.

Radiocarbon Dating

Radiocarbon is also known as carbon-14, or C-14 because there are 14 particles in its nucleus-six protons and eight neutrons. All lvimg things as they build and repair tissues. However, when an organism dies, it stops taking in C-14. The C-14 already present in the organism starts to decay to nitrogen-14 (N-14). Radiocarbon dating is useful for measuring the age of the remains of organisms that died up to about 60,000 years ago.

Absolute Ages of Rocks

Simalarly scientists can describe the ages of some kinds of rocks numerically. By measure g the absolute ages of rocks, geologist have developed accurate historical records for many geologic formations. Scientists have been able to determine the absolute ages of rocks and other objects since the beginning of the twentieth century.

Dating Sedimentary Rock

The grains in many sedimentary rocks come from a variety of weathered rocks from different locations. The radioactive isotopes within these grains generally record the ages of the grains—not the time when the sediment was deposited.

Half-Life

The rate of decay form parent Isotopes into daughter Isotopes is different for different radioactive elements. When half the parent Isotopes have decayed into daughter Isotopes, the Isotope has reached one Half- Life. At this point fifty percent of the isotopes are parents and fifty percent of the Isotopes are daughters. After three Half-Lives, the half again of the remaining parent Isotopes have decayed into daughter Isotopes.

Dating Igneaus Rock

U-235 is often trapped in the minerals of igneaus rocks that crystallize from hot molten magma. Scientist measure the ratio of U-235 to Pb-207 in a mineral to determine how much time has passed since the mineral formed.