The uranium-235 to lead-207 decay series is marked by a half-life of 704 million years.

These differing rates of decay help make uranium-lead dating one of the most reliable methods of radiometric dating because they provide two different decay clocks.

Learn about half-life and how it is used in different dating methods, such as uranium-lead dating and radiocarbon dating, in this video lesson. As we age, our hair turns gray, our skin wrinkles and our gait slows.

geologic dating lesson-14geologic dating lesson-77

The thing that makes this decay process so valuable for determining the age of an object is that each radioactive isotope decays at its own fixed rate, which is expressed in terms of its half-life.

So, if you know the radioactive isotope found in a substance and the isotope's half-life, you can calculate the age of the substance. Well, a simple explanation is that it is the time required for a quantity to fall to half of its starting value.

During the breaks, students will construct a geologic timeline of their own in the classroom and do simple calculations to determine how long amounts of time can lead to impressive changes in the height of the Himalayan Mountains and the size of a group of reptiles. Francis Mac Donald is an Assistant Professor of Geology in the Earth and Planetary Science Department at Harvard University.

[ Correction: There is an incorrect statement in this video lesson that the pyramids were built 2.500 years ago. Francis' research focuses on the interactions of climate, life, and ocean geochemistry in deep time.

Included are several videos on the topic of evolution.

is a link to the original article on the lizard research done by Jonathan Losos and his colleagues, entitled Adaptive differentiation following experimental island colonization in Anolis lizards.

This work begins with field studies of Neoproterozoic and Paleozoic strata in Arctic Alaska, northwest Canada, Mongolia and Namibia.

Watch lectures by Harvard faculty and other scientists and naturalists, presented by the Harvard Museum of Natural History - where much of this BLOSSOMS video lesson was filmed.

site, presented by Starting Point: Teaching Entry Level Geoscience, provides resources for teaching about radiometric dating.

website, Time Scale Creator, enables you to explore and create charts of any portion of the geologic time scale from an extensive suite of global and regional events in Earth History.

This site is presented by The Science Education Resource Center (SERC), an office of Carleton College that works to improve education through projects that support educators.