Question

Uranium-series dating is based on the radioactive decay of uranium isotopes, and is very useful for the period 500,000-50,000 years ago, which is outside the limits of radiocarbon dating. This method is used to date _________.

Answer 1

Answer:

younger than 50,000 years and older than 100 years

Explanation:

Carbon-14 is produced in the upper atmosphere when cosmic rays bombard nitrogen atoms. The ensuing atomic interactions create a steady supply of c14 that rapidly diffuses throughout the atmosphere. Plants take up c14 along with other carbon isotopes during photosynthesis in the proportions that occur in the atmosphere. animals acquire c14 by eating the plants (or other animals). During the lifetime of an organism, the amount of c14 in the tissues remains at an equilibrium since the loss (through radioactive decay) is balanced by the gain (through uptake via photosynthesis or consumption of organically fixed carbon). However, when the organism dies, the amount of c14 declines such that the longer the time since death the lower the levels of c14 in organic tissue. This is the clock that permits levels of c14 in organic archaeological, geological, and paleontological samples to be converted into an estimate of time.

half-life of radiocarbon is actually 5730 ± 40 years

Since there are practical limits to the age range of the method, most samples must be younger than 50,000 years and older than 100 years.