Determining absolute ages by radiometric dating
This tree ring record has proven extremely useful in creating a record of climate change, and in finding the age of ancient structures. The thick, light-colored part of each ring represents rapid spring and summer growth.
The thin, dark part of each ring represents slow autumn and winter growth.
To study these patterns, scientists drill deep into ice sheets, producing cores hundreds of meters long.
Scientists analyze these ice cores to determine how the climate has changed over time, as well as to measure concentrations of atmospheric gases.
Not surprisingly, these methods resulted in wildly different estimates, from a few million years to "quadrillions of years".
In 1892, William Thomson (later known as Lord Kelvin) calculated the age of Earth in a systematic fashion (Figure 11.24).
Fossils are generally found in sedimentary rock not igneous rock.
Sedimentary rocks can be dated using radioactive carbon, but because carbon decays relatively quickly, this only works for rocks younger than about 50 thousand years.
Find additional lessons, activities, videos, and articles that focus on relative and absolute dating.
As we learned in the previous lesson, index fossils and superposition are effective methods of determining the relative age of objects.
The universe is full of naturally occurring radioactive elements.