Potassium has a half-life of 1. Principles and applications of geochemistry: Teach your students about absolute dating: While uranium is water-soluble, thorium and protactinium are not, and so they are selectively precipitated into ocean-floor sedimentsfrom which their ratios are measured. Main article: Cell Division 2:
The Geologic Time Scale2-volume set.
To establish the age of a rock or a fossil, researchers use some type of clock to determine the date it was formed. In other projects Wikimedia Commons. Stratigraphy and biostratigraphy can in general provide only relative dating A was before Bwhich is often sufficient for studying evolution. Reversed polarity is when the magnetic "north" is near the geographic south pole. The age of the earth.