How does radioactivity allow us to estimate the Earth's age?

Answer 1

Radioactive or radiometric dating allows us to estimate the Earth's age by giving us the actual age of rock within a range of several million years. Radiometric dating is based on the scientific law of radioactive decay and the half-life of radioactive elements. Uranium and some other elements decay into lead over time at a specific rate. Knowing the content of these elements in the makeup of a rock allows its age to be calculated. Currently, the oldest rocks of Earth origin are estimated to be over 4 billion years old.

Answer 2

Radioactive materials are useful for measuring geologic time because as time passes elements are always reacting with each other. For example a commonly known radioactive material used is Carbon-13 because what was once normally carbon-12 over time developed into carbon-13 which happens to be radioactive.

Answer 3

Radioactive carbon-14 atoms exist naturally. However, only 1.3 × 10-12 percent of all carbon atoms are the carbon-14 isotope. This is why they do not pose danger to us.

The ratio of radioactive carbon-14 atoms to stable carbon-12 atoms in the atmosphere has remained constant over thousands of years. Although carbon-14 naturally decays, it is also continually being formed.

Because the ratio of carbon-14 to carbon-12 in atmospheric CO2 is constant, the intake of CO2 by a plant results in a constant ratio of the two isotopes in the plant's body while it is alive. However, when the plant dies it will no longer take in CO2. As a result, the carbon-14 decaying in the dead plant will not be replenished by a "fresh supply" of more CO2, resulting in the ratio of carbon-14 to carbon-12 decreasing over time.

Because animals eat plants, the ratio of carbon-14 to carbon-12 in them also decreases once they die, since the carbon-14 cannot be replenished.

This process of dating using carbon-14 is used by paleontologists. Paleontologists burn a small sample of a fossil to react the carbon in it with oxygen, to form CO2. The CO2 that contains carbon-14 will be radioactive, and the amount can be easily measured using a radiation counter. Burning is done to facilitate measuring the level of carbon-14.

Carbon-14 has a half life of about 5730 years. This means that in a given sample of a carbon-containing substance, (without the carbon-14 being replenished) the ratio of carbon-14 to carbon-12 will decrease by half every 5730 years.

The relatively short half-life of carbon-14 (5730 years) means that the amount of carbon-14 remaining in materials and objects older than about 80,000 years is too small to be measured with today's equipment.

However, the abundance of other atoms with longer half-lives, such as uranium-238 (half-life 4.5 × 109 years) can be measured in place of carbon-14. Geologists measure the amounts of other radioactive metal isotopes such as uranium-238, rubidium-84 and potassium-40 found in rocks to determine their age.

As well as using carbon-14 to carbon-12 decay, geologists also measure the decay of potassium-40 to argon in dating rocks. The decay of rubidium-87 to strontium-87 is used to check potassium-argon dates, and is much more accurate because neither isotope is diffused by heat.

The rubidium technique was used by scientists to determine the age of the moon. Measurements using uranium-238 were used to determine the age of the Earth.

In radioactive dating, the initial conditions are taken as known: in the case of carbon-14 dating, the ratio of carbon 14 to carbon 12 is determined by the ratio in the atmosphere. In the case of radioactive dating of rocks, the quantity of the product of radioactive decay is generally taken to be nil. It is also assumed that no addition or subtraction of material has taken place by non-radioactive means.

Answer 4

Radio active materials are useful for scientists in studying how long the fossil has been around.Using carbon elements in the bone's results maybe wrong on how long the carbon elements disappeared Dating fossils they use a system of eras to know how long the creature has been around.Then they go over and calculate how long it has existed by using Radio active materials such as carbon and many others.

Answer 5

When radioactive isotopes decay, they give off radiation. Over time, the amount of radiation given off decreases as more and more of the substance decays, and there is less of the original radioactive substance left to decay. The time taken for the radioactivity to half (i.e. for the amount of radiation given off to halve) is known as the half-life. We know the half-lives of many radioactive isotopes, including those found in rocks. We can measure the radioactivity of rocks and, based on the composition of the rock (i.e. what minerals it contains), we can determine from the half-life the age of the rock itself.

Answer 6

Radioactive substances decay at a constant rate. Using the radioactive elements in geologic structures gives science a good idea concerning the age of it.

Answer 7

To date materials such as rocks,or any other unknown date of time material

Answer 8

Their half-lives and fissile chain-reactions are know, so measuring the ratio of isotopes gives a ratio that can be applied to the half-lives to calculate when the rock was formed.

Answer 9

An important isotope is carbon-14.