Dating
In geology, to "date" something means to find out its age. Different dating methods are used
depending on the type and approximate age of material being dated. Lead isotopes can be used for dating sediments
less than a 150 years old, while carbon isotopes are used for material up to 20,000-40,000
years old. Much older material is dated using long-life isotopes such as uranium and thorium, and
the natural decay clocks some amino acids. In our study of Bear Lake, the sediments we're
studying range in age from modern, as with our sediment traps, to
more than 20,000 years old, like the material in our piston cores.
Some of the GLAD800 core material is probably millions of years old.
How we use the dates
Before we can make accurate interpretations from our results, we need to know when the changes
we're detecting actually happened. The environmental context of a change is often just as
important as the change itself. For instance, large
icebergs calving off the
Antarctic coast are creating new areas of open ocean in the Ross
Sea. While we are concerned that this may be the result of global warming, the change is still
within the range of natural variability for the interglacial period we're in. If we found
evidence of similar open ocean areas in the Ross Sea from 20,000 years ago, at the height of
the glacial period, it would indicate a dramatic change in climate. It is the context that
affects our response to the data. In order to know the context, we must know the age of the
changes we're examining.
Follow the links below to learn more about the different dating methods we're using for the Bear Lake Project.
To learn more about dates and geochronology, check out these sites:
U.S. Department of the Interior | U.S. Geological Survey