# Radiometric method for dating volcanic deposits Reds adult chat

because the decay rate is logarithmic, radiocarbon dating has significant upper and lower limits.

His result was in close agreement with his estimate of the age of the earth.This estimate was actually reduced over his lifetime to between 20 Ma and 40 Ma and eventually to less than 10 Ma. Perry, in particular, a noted physicists and former assistant to Kelvin, showed that cooling calculations using different but equally likely assumptions and data resulted in ages for the Earth of as much as 29 Ga.Of course, later scientists, like John Perry and T. After this came to light, Kelvin admitted that he might just as well have set his original upper limit on the age of the Earth at 4,000 Ma instead of 400 Ma.This just goes to show that just because independent estimates of age seem to agree with each other doesn't mean that they're correct - despite the fact that this particular argument is the very same one used to support the validity of radiometric dating today.Other factors and basic assumptions must also be considered.

Each radioactive isotope has its own rate, expressed in terms of its half-life.