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Chapter 12

A Trip Through Geologic Time

Question Answer
Fossil The reserved remains or traces of an organism that lived in the past.
Mold A type pf fossil that is hollow area in sediment in the shape of an organism or part of an organism.
Cast A fossil that is a solid copy of an organism's shape, formed when minerals seep into a mold.
Petrified Fossil A fossil in which minerals replace all or part of an organism.
Carbon Film A type of fossil consisting of an extremely thin coating of carbon on rock.
Trace Fossil A type of fossil that provides evidence or the activities of ancient organisms.
Paleontologist A scientist who studies fossils to learn about organisms that live long ago.
Evolution Change over time; the process by which modern organisms have descended from ancient organisms.
Extinct Term used to refer to a group of related organisms that has died out and has no living members.
Relative Age The age of a rock compared to the ages of other rocks.
Absolute Age The age of a rock given as the number of years since the rock formed.
Geologic Time Scale A record of the geologic events and life forms in Earth's history.
Era One of the three long units of geologic time between the Precambrian and the present.
Period One of the units of geologic time into which geologists divide eras.
Invertebrate An animal without a backbone.
Vertebrate An animal with a backbone.
Amphibian A vertebrate whose body temperature is determined by the temperature of its environment, and that lives its early life in water and its adult life on land.
Law of Superposition The geologic principle that states that in horizontal layers of sedimentary rock, each layer is older that the layer above it and younger than the layer below it.
Extrustion An igneous rock layer formed when lave flows on Earth's surface and hardens.
Fault A break in Earth's crust along which rock moves.
Index Fossil Fossils of widely distributed organisms that lived during a geologically short period.
Unconformity A gap in the geologic record that shows where rock layers have been lost due to erosion.
Created by: creedenb