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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. |