key points and defonitions
principle of superposition- the principle that in a series of stratified sedimentary rocks the lowest stratum is the oldest.
strata-A layer or a series of layers of rock in the ground: "a stratum of flint".relative dating-in archaeology, the arrangement of artifacts or events in a sequence relative to one another but without ties calendrically measured time; the arrangement of artifacts in a typological sequence or seriation.
index fossils- a fossil used to determine the relative age of the layer of rock.
half-life- the amount of time that a given amount of radioactive substance takes to be reproduced by one-half.
radiometric dating-by measuring the amounts of such elements in a rock and by knowing the half-life of the parent a geologist can calculate the absolute age of rock.
radiocarbon dating-a type of radiometric dating to find out when recent events in earths history occurred.
eons-the largest divisions in the scale.
eras-eons are divided into eras.
periods-eras are divided into periods.
precambrian-this vast expanse of time.
rodinia-scientist think the earliest supercontinent, rondia, formed during this time , about 1.1 billion years ago.
paleozoic era-the second era on the geologic time scale the era in which the first plants and animals appeared.
mesozoic era-the third era on the geologic time scale the era in which dinosaurs were the dominant life form on earth.
cenozoic era-the fourth and current erain which humans envolved.
pangaea-the name of the second supercontinent thought to have existed approximately 350million years ago.
laurasia-the northern part of the supercontinent pangaea.
gondwanaland-the southern part of pangaea.
strata-A layer or a series of layers of rock in the ground: "a stratum of flint".relative dating-in archaeology, the arrangement of artifacts or events in a sequence relative to one another but without ties calendrically measured time; the arrangement of artifacts in a typological sequence or seriation.
index fossils- a fossil used to determine the relative age of the layer of rock.
half-life- the amount of time that a given amount of radioactive substance takes to be reproduced by one-half.
radiometric dating-by measuring the amounts of such elements in a rock and by knowing the half-life of the parent a geologist can calculate the absolute age of rock.
radiocarbon dating-a type of radiometric dating to find out when recent events in earths history occurred.
eons-the largest divisions in the scale.
eras-eons are divided into eras.
periods-eras are divided into periods.
precambrian-this vast expanse of time.
rodinia-scientist think the earliest supercontinent, rondia, formed during this time , about 1.1 billion years ago.
paleozoic era-the second era on the geologic time scale the era in which the first plants and animals appeared.
mesozoic era-the third era on the geologic time scale the era in which dinosaurs were the dominant life form on earth.
cenozoic era-the fourth and current erain which humans envolved.
pangaea-the name of the second supercontinent thought to have existed approximately 350million years ago.
laurasia-the northern part of the supercontinent pangaea.
gondwanaland-the southern part of pangaea.