Earth’s Past and Geologic Time – Flashcards
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absolute dating
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A technique used to determine the actual age of a fossil
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radiometric dating
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Calculate the absolute age of a rock by knowing the half life of an isotope that is present in the rock
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relative-age dating
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chronological ordering of geological strata featurs fossils or events without reference to their absolute age
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radiocarbon dating
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A chemical analysis used to determine the age of organic materials based on their content of the radioisotope carbon-14
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eras
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a major division of time that is a subdivision of an eon and is itself subdivided into periods
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periods
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a major division of time that is a subdivision of an era and is itself subdivided into epochs
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epochs
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the shortest span of geologic time
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eons
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the longest span of geologic time
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precambrian
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noting or pertaining to the earliest era of earth history, ending 570 million years ago, during which the earth's crust formed and life first appeared in the seas. See table under geologic time.
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natural selection
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A process in which individuals that have certain inherited traits tend to survive and reproduce at higher rates than other individuals because of those traits. (Charles Darwin)
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trace fossil
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A type of fossil that provides evidence of the activities of ancient organisms
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half-life
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The time required for one half of the atoms of a radioisotope to emit radiation an decay products
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superposition
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A principle that states that younger rocks lie above older rocks if the layers have not been disturbed.
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uniformitarianism
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A principle that geologic processes that occurred in the past can be explained by current geologic processes
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unconformities
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Gaps in rock sequences
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Mesozoic era
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middle life; rise of mammals and dinosaurs; the rise of birds; extinction of dinosaurs, rise of flowering plants
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Cenozoic era
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(The "Age of Mammals"). It saw the emergence of familiar life forms, humans, the modern look of the continents, and a cooling climate.
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Paleozoic era
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first vertebrates ERA OF THE FISH amphibians. Permian extinction, oceans poisoned, reptiles survived
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movement of tectonic plates may cause a change in _
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size of organisms (they grow larger as continents seperate)
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organic evolution
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change of organisms over geologic time
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paleontology
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Study of fossils
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fossils
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Preserved remains of once-living organisms
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hard parts
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bones, shells, teeth, etc.
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permineralized remains
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fossils in which the spaces inside are filled with minerals from groundwater
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carbon film
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thin film of carbon residue preserved as a fossil
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mold
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cavity in rock left when the hard parts of an organism decay
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cast
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the outcome of sediments that have washed into a mold
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index fossil
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abundant, geographically widespread organisms that existed for relatively short periods of time
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carbon 14 dating
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used to date bones, wood, and charcoal up to 75,000 years old
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angular unconformity
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rock layers are tilted, and younger sediment layers are deposited horizontally on top of the eroded and tilted layers
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disconformity
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layer of horizontal rock once exposed and eroded before younger rocks formed over it
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nonconformity
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sedimentary rock forms over eroded metamorphic or igneous rock
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radioactive decay
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unstable isotopes break down into other isotopes and particles
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how old Earth is
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4.5 billion years old
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age of oldest known rocks
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3.96 million years old
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original remain
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actual organism or parts of organism protected from decay
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geologic time
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scale used by paleontologists to represent evolutionary time
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trilobite
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famous index fossil
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species
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organisms that normally reproduce only with other members of their group
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artificial selection
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breeding individuals with desired characteristics; humans use this when breeding domestic animals
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new species
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evolves according to natural selection
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pangea
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famous landmass, "supercontinent"
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extinction of trilobites
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dropping of sea level during the paleozoic era
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cyanobacteria
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blue-green algae, one of Earth's first organisms
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when the first humans appeared
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from about 140,000-200,000 years ago.
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vertebrates
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Animals with backbones
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invertebrates
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animals without backbones
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reptiles
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animals evolved from amphibians
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amphibians
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animals that live on land but return to water to reproduce
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dinosaur era
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Mesozoic era
