Because of this, magnetic minerals in rocks are excellent recorders of the orientation, or polarityof the Earth's magnetic field. Address 1. Author information: Principles and Applications. Creature Cast. Age estimates can be cross-tested by using different isotope pairs. Thus it can be demonstrated that the magnetic field of the earth has reversed itself dozens of times throughout earth history.
Since animal species change over time, the fauna can be arranged from younger to older.
Direct dating of human fossils.
Phylogenetic trees are the family trees of particular groups of plants or animals, showing how all the species relate to each other. The list is too long to mention here, so a couple of examples are provided to get you going on your search for programs in your area:. Register Sign In. Layers of rock are deposited horizontally at the bottom of a lake principle of original horizontality. The rate of decay for many radioactive isotopes has been measured and does not change over time. Through geologic time, the polarity of the Earth's magnetic field has switched, causing reversals in polarity.