Table of Contents
- 1 How old would a rock be if it has equal amounts of uranium and lead?
- 2 Why can uranium-238 be used to determine the age of rocks even though they are extremely old?
- 3 How do you calculate absolute age?
- 4 How much uranium 206 is in the rock sample?
- 5 How can we accurately determine the age of a rock or fossil by measuring its?
How old would a rock be if it has equal amounts of uranium and lead?
Figure 11.26: Zircon crystal. Uranium-lead dating can be used to date igneous rocks from 1 million years to around 4.5 billion years old. Some of the oldest rocks on Earth have been dated using this method, including zircon crystals from Australia that are 4.4 billion years old.
How old is a rock which contains uranium-238 and has undergone 2 half lives?
A rock containing U-238 weighs 10 mg when it was unearthed. How much mass of radioactive parent isotope will be present after 4 half-lives. 7. A rock is found to be 2.84 billion years old using U-235 dating….KEY: Half-Life Calculations.
| Element | Carbon |
|---|---|
| Parent Isotope | C-14 |
| Daughter Isotope | N-14 (Nitrogen) |
| Half-life | 5,730 years |
Why can uranium-238 be used to determine the age of rocks even though they are extremely old?
The more lead the rock contains, the older it is. The long half-life of uranium-238 makes it possible to date only the oldest rocks. This method is not reliable for measuring the age of rocks less than 10 million years old because so little of the uranium will have decayed within that period of time.
How do we determine the age of rocks?
The age of rocks is determined by radiometric dating, which looks at the proportion of two different isotopes in a sample. Radioactive isotopes break down in a predictable amount of time, enabling geologists to determine the age of a sample using equipment like this thermal ionization mass spectrometer.
How do you calculate absolute age?
The formula for calculating absolute age of a layer by this method of counting is: Absolute age in years (A) = time elapsed since the formation of the most recent layer (R) plus (the number of layers (N) lying above the layer in question multiplied by the duration (D) of the depositional cycle).
How is uranium used to date rocks?
Uranium-lead dating can be used to find the age of a uranium-containing mineral. Uranium-238 decays to lead-206, and uranium-235 decays to lead-207. The two uranium isotopes decay at different rates, and this helps make uranium-lead dating one of the most reliable methods because it provides a built-in cross-check.
How much uranium 206 is in the rock sample?
Problem #58: A sample of rock contains 64.27 mg of U-238 (isotopic mass 238.0508 amu) and 22.66 mg of Pb-206 (isotopic mass 205.9745 amu).
How old is a rock sample that contains uranium-235 and lead 207 in equal amounts?
704 million years
RADIOMETRIC TIME SCALE
| Parent Isotope | Stable Daughter Product | Currently Accepted Half-Life Values |
|---|---|---|
| Uranium-238 | Lead-206 | 4.5 billion years |
| Uranium-235 | Lead-207 | 704 million years |
| Thorium-232 | Lead-208 | 14.0 billion years |
| Rubidium-87 | Strontium-87 | 48.8 billion years |
How can we accurately determine the age of a rock or fossil by measuring its?
Relative dating is used to determine a fossils approximate age by comparing it to similar rocks and fossils of known ages. Absolute dating is used to determine a precise age of a fossil by using radiometric dating to measure the decay of isotopes, either within the fossil or more often the rocks associated with it.