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34 Cards in this Set
- Front
- Back
atom
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the smallet particle of an element
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element
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A type of matter in which all the atoms are the same
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radioactive decay
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The breakdown of a radioactive element, releasing particles and energy
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half-life
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The time it takes for half of the atoms of a radioactive element to decay
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geologic time scale
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a record of the geologic events and life forms in Earth's history
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era
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one of the 3 long units of geologic time between the Precambrian and the present
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period
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one of the units of geologic time into which geologists divide eras
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comet
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a ball of ice and dust that orbits the sun
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continental drift
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the slow movement of the continents over earths surface caused by forces inside earth
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invertebrate
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an animal without a backbone
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vertebrate
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an animal with a backbone
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amphibian
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a vertebrate that lives part of its life on land part of its live in water
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reptile
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a vertebrate with scaly skin that lays eggs with tough, leathery skin
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mammal
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a warm-blooded vertebrate that feeds it young milk
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mass extinction
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when many types of living things become extinct at the same time
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fossil
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the preserved remains or traces of living things
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sedimentary rock
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the type of rock that is made of hardened sediment
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mold
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a fossil formed when an organism buried in sediment dissolves, leaving a hollow area
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cast
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a fossil that is a solid copy of an organism's shape, formed when minerals seep into a mold
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petrified fossil
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a fossil in which minerals replace all or part of an organism
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carbon film
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a type of fossil consisting of an extremely thin coating of carbon on rock
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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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paleontologists
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a scientist who studies fossils to learn about organisms that lived long ago
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scientific theory
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a well-tested concept that explains a wide range of observations
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evolution
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the process of by which water all the different kinds of living things have changed over time
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extinct
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describes a type of organism that no longer exists anywhere on Earth
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relative age
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the age of a rock compared to the ages of rock layers
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absolute age
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the age of a rock given as the # of years since the rock formed
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law of superposition
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the geologic principle that states that in horizontal layers of sedimentary rock,each layer is older than the layer above it and younger than the layer below it
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extrusion
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an igneous rock layer formed when lava flows onto Earth's surface and hardens
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intrusion
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an igneous rock layer formed when magma hardens beneath Earth's surface
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fault
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a break or crack in Earth's lithosphere along which rocks move
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index fossil
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fossils of widely distributed organisms that lived during only one short period
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uncomformity
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a place where an old, eroded rock surface is in contact with a newer rock layer
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