8.E.2

Terms in this set (22)

Absolute or Carbon Dating
Any method of measuring the age of an event or object in nearly-exact year. Radioactive dating measures the decay of Carbon-14 or Uranium-238 to calculate age.
Carbon-14: previously living objects
Uranium-238: rocks & minerals
Absolute age
the true age of a rock or fossil, tells scientists the number of years ago a rock
Relative age
the geologic age of a fossil organism, rock, or geologic feature or event defined relative to other organisms, rocks, or features or events rather than in terms of years
Law of Superposition
States that the oldest rock layers lay on the bottom and the youngest rocks are on top in any undisturbed sequence of sedimentary rock layers
Unconformity
Any gap or inconsistency in the rock record (layers of rock) caused by plate movement, weathering, etc.
Evolution
any process of formation or growth; development
Fault
a fracture or fissure in the Earth's crust in which there is movement on either side of the fracture; a place where sections of the crust of the Earth move relative to each other
Pangaea
a hypothetical supercontinent that included all current land masses, believed to have been in existence before the continents broke apart during the Triassic and Jurassic Periods
continental drift
Theory that states that the gradual shifting of Earth's plates causes continents to change their global positions over time
Fossil
the remains or impression of a prehistoric organism preserved in petrified form or as a mold or cast in rock
Index fossils
A fossil that is used to help determine the approximate age of the rocks around it, because it:
Is widespread, over multiple continents
Existed for a relatively short period of time
Fossil record
a historical representation of the changes in life and geography over time as found in fossils in various layers of rock
Cast fossil
A fossil that forms when sediment fills in a mold fossil creating a 3-d replica of the organism
Mold fossil
A fossil that forms when an organism dies and is covered by sediment. As it decays an empty space is left where the body used to be
Trace fossil
A fossil of a footprint, trail, or other evidence of an organism but not the organism itself.
Carbon film fossil
a fossil that forms when a delicate organism or part decays leaving a thin film of carbon in the silhouette (shape) of the original organism
Geologic time scale
The method used to divide the millions of years of Earth's history into manageable parts. Divisions are based on what type of life was dominant on Earth or major geologic events
Cenozoic Era
The "Age of Mammals". Began about 66 million years ago
Mesozoic Era
The "Age of Dinosaurs". Began about 245 million years ago
Paleozoic Era
Began about 544 million years. Defined by the rapid and dramatic increase of diverse species on Earth
Cambrian explosion
Period of time in which the number and types of multicellular living organisms increased suddenly and dramatically. Ancestors of almost all current organisms appeared.
Permian extinction
The "Great Dying". Between 90% and 96% of all species on Earth went extinct. Only event to result in mass extinction of insects.
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