By F.A. McKinney. Approximate grade level 9-12.
More comprehensive than the site "Time and Change" by the US Geological Survey, this site uses a block diagram showing realistically complicated stratigraphic relationships, and a real isotopic decay sequence.
Students deduce the relative ages of the rock
units in the block diagram, and then use isotopic evidence to determine the
ages of the various igneous rocks present. Ages of fossils in the sedimentary
rocks are seen to be bracketed by the ages of the igneous rocks.
|
|
|
|