High Quality Content by WIKIPEDIA articles! The geologic record in stratigraphy, paleontology and other natural sciences refers to the entirety of the layers of rock strata — deposits laid down in volcanism or by sediment deposition of weathering detritus (clays, sands etc.) including all its fossil content and the information it yields about the history of the Earth: its past climate, geography, geology and the evolution of life on its surface. According to the law of superposition sedimentary and volcanic rock layers are deposited on top of each other. They harden over time to become a solidified (competent) rock column, that may be intruded by igneous rocks and disrupted by tectonic events over time.