Theory of Continental Drift Continental Drift : Movement of rigid continental crust over plastic asthenosphere Plate Tectonics : geophysical processes producing and destroying oceanic crust Basic Observation : Fit of continental margins Snider-Pelligrine, Alfred L. Wegener Primary Observation: fit of continental margins Book Geology : trans-Atlantic alignment of mountains, alignment of rock strata Geophysics : change in elevation implies crustal plasticity Paleontology : Glosopteris flora distribution in S. Hemisphere Paleoclimatology : tropical coal beds in Northern Europe, tillites in tropical Africa Biogeography : marsupials and Nothofagus in South America and Australia. Wegener Book revision Match of continental margins as in book Crust : Continental felsic rocks vs.
22.3 Half Life and Radiometric Dating
Classroom Resources | Radioactive Decay and Seafloor Data | AACT
Radiometric dating , radioactive dating or radioisotope dating is a technique which is used to date materials such as rocks or carbon , in which trace radioactive impurities were selectively incorporated when they were formed. The method compares the abundance of a naturally occurring radioactive isotope within the material to the abundance of its decay products, which form at a known constant rate of decay. Together with stratigraphic principles , radiometric dating methods are used in geochronology to establish the geologic time scale. By allowing the establishment of geological timescales, it provides a significant source of information about the ages of fossils and the deduced rates of evolutionary change. Radiometric dating is also used to date archaeological materials, including ancient artifacts. Different methods of radiometric dating vary in the timescale over which they are accurate and the materials to which they can be applied. All ordinary matter is made up of combinations of chemical elements , each with its own atomic number , indicating the number of protons in the atomic nucleus.
The simplest form of isotopic age computation involves substituting three measurements into an equation of four variables, and solving for the fourth. The equation is the one which describes radioactive decay:. Solving the equation for "age," and incorporating the computation of the original quantity of parent isotope, we get:. Some assumptions have been made in the discussion of generic dating, for the sake of keeping the computation simple.
Need Help? Last updated July 14, In this activity, students will apply their understanding of radioactive decay to analyze and interpret the meaning of Atlantic seafloor isotope data. Students will then use their results to suggest past changes that have occurred with the seafloor.