What is a fossil?
A fossil is any trace of a past life form. A fossil may consist of the imprint of a leaf in sedimentary rock, or it may be the remains of a tooth or bone of a vertebrate. Most fossils are preserved in sedimentary rocks. They form when sediments cover a corpse or an object that is dropped into water.
How are fossils formed?
Fossils are formed when organisms die and are buried by sediments. Over time, the sediments turn to rock and the organic matter is preserved. The process of fossilization can take a very long time, and many variables must be present for it to occur. Factors such as the right environment, quick burial, and lack of oxygen all contribute to the formation of fossils.
What is 14C?
14C is a radioactive isotope of carbon with a half-life of 5730 years. This means that if you start with a sample of 100 carbons, in 5730 years you will only have 50 carbons left. This is useful for dating because it can be used to date organic materials.
What is the half-life of 14C?
The half-life of 14C is 5730 years. So, if a fossil has a 14C level of 920 compared to living organisms, it is 5730 years old.
How is 14C used to date fossils?
14C, or radiocarbon, is a radioactive isotope of carbon with an atomic nucleus containing 6 protons and 8 neutrons. Its presence in organic materials is the basis of the radiocarbon dating method pioneered by Willard Libby and colleagues to date archaeological, geological and hydrogeological samples.
14C is produced in the upper atmosphere by cosmic ray bombardment of nitrogen atoms. The resulting 14C combines with atmospheric oxygen to form carbon dioxide, which is then incorporated into plants during photosynthesis. Animals eat plants and take in 14C as well, so every living creature has a constant level of 14C to 13C (the stable isotope of carbon with an atomic nucleus containing 6 protons and 7 neutrons).
When an organism dies, it stops taking in new 14C, and the existing isotope decays with a half-life of 5,730 years. By measuring the ratio of remaining 14C to 12C in a sample, its age can be determined.
How old is the fossil?
The fossil is most likely 920 years old. This is because the 14c level is compared to living organisms.
What is the half-life of the fossil?
To find the half-life of the fossil, we must first calculate the initial 14C activity. This can be done by using the following equation: A=A0e^-kt. In this equation, A is the 14C activity at time t, A0 is the initial 14C activity, k is the first order rate constant for 14C decay (0.000121 per year), and t is time in years. Plugging in the values from the problem, we get that A=920e^-(0.000121*1529). This gives us an initial 14C activity of approximately 9,110,000 dpm/gC. We can then use this value to find the half-life of the fossil by using the following equation: t1/2=ln(2)/k. Plugging in our values, we find that t1/2=ln(2)/(0.000121)=5,730 years. Therefore, the half-life of the fossil is 5,730 years and it is 1529 years old.
How is the fossil’s age calculated?
The fossil’s age is calculated by using the 14c level. The 14c level is the amount of carbon-14 found in the fossil compared to living organisms.