Museum Hours
10:00 am - 5:00 pm
on Weekdays &
1:00 pm - 5:00 pm
on Weekends!
Doors close at 4:45pm.
We are closed on
some holidays

Fossil Dating

Until the early 1900’s it was impossible to fix an absolute age to any fossils. Before then, only relative ages could be determined by a method called superposition. Fossils found in lower rock layers were presumed older than fossils found in higher layers.

In 1905 a Yale chemist, Bertram Boltwood, found that there was a relationship between the amount of lead and uranium in mineral samples and their relative ages. Boltwood felt that the uranium (parent element), a radioactive element, gradually decayed into lead (daughter element). He was able to calculate a mathematical formula for the rate at which this decay occurs.

The rate of decay of radioactive elements is measured in “half-lifes.” A half-life is the length of time needed for one-half of the original amount of parent element to decay. The half-life of uranium was found to be 4,500,000,000 years. To determine the age of a mineral sample the ratio of parent/daughter element is calculated and from the decay curve a date is established.