Chapter 13 Earth Science Clues to Earth’s Past
Words to Know – Section 1 Fossils fossil Permineralized remains Carbon film Mold Cast Index fossil
remains, imprints, or traces of prehistoric organisms that can tell when and where organisms once lived and how they lived. fossil
Fossils in which that spaces inside are filled with minerals from groundwater. Permineralized remains
Thin film of carbon residue preserved as a fossil. Carbon film
A type of body fossil that forms in rock when as organism with hard parts is buried, decays or dissolves, and leaves a cavity in the rock. mold
A type of body fossil that forms when crystals fill a mold or sediments wash into a mold and harden into rock. cast
Remains of species that existed on Earth for relatively short periods of time, were abundant and widespread geographically, and can be used by geologists to assign the ages of rock layers. Index fossil
Words to Know – Section 2 Relative Ages of Rocks Principle of superposistion Relative age unconformity
States that in undisturbed rock layers, the oldest rocks are on the bottom and the rocks become progressively younger toward the top. Principle of superposition
The age of something compared with other things. Relative age
Gap in the rock layer that is due to erosion or periods without any deposition. unconformity
Words to Know – Section 3 Absolute Age of Rocks Absolute age Radioactive decay Half-life Radiometric dating uniformitarianism
Age, in years, of a rock or other object; can be determined by using properties of the atoms that make up materials. Absolute age
Process in which some isotopes break down into other isotopes and particles. Radioactive decay
Time it takes for half the atoms of an isotope to decay. Half-life
Process used to calculate the absolute age of rock by measuring the ratio of parent isotope to daughter product in a mineral and knowing the half-life of the parent. Radiometric dating
Principle stating that Earth processes occurring today are similar to those that occurred in the past. uniformitarianism