Earth Science Chapter 9 – Flashcards
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the interval of time in the geologic time scale from Earth's formation to the beginning of the Paleozoic era, from 4.6 billion to 542 million years ago. It contains the first three eons of Earth's history.
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Precambrian Time
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an episode during which large numbers of species become extinct.
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Mass Extinction
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outlines the development of Earth and of life on Earth.
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Geologic Time Scale
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the explanation for the extinction of the dinosaurs.
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Impact Hypothesis
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the geologic era that followed Precambrian time and that lasted from 542 million to 251 million years ago.
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Paleozoic Era
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the process of change by which new species develop from preexisting species over time.
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Evolution
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the current geologic era, which began 65.5 million years ago; also called the Age of Mammals.
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Cenozoic Era
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large areas of exposed Precambrian rocks.
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Shield
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an ordered arrangement of rock layers that is based on the relative ages of the rocks and in which the oldest rocks are at the bottom.
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Geologic Column
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What does the symbol Ma stand for?
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Millions of years ago.
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How many eons is the geologic time broken into?
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4 eons: Hadean, Archean, Proterozoic, and the Phanerozoic eon.
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What does Precambrian time consist of?
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88% of Earth's history.
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How do you describe Precambrian rock?
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Precambrian rocks have been so severely deformed and altered by tectonic activity that the original order of rock layers is rarely identifiable.
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When did Pangea form?
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During the Permian period.
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What were the two main dinosaur groups during the Jurassic period?
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The saurischians, "lizard-hipped" dinosaurs and the ornithischians, "bird-hipped" dinosaurs.
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What is the Cenozoic Era known as?
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The age of mammals.
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What is Precambrian rock difficult to interpret?
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Nearly half of the valuable mineral deposits in the world occur in the rocks of Precambrian shields and they contain few fossils.
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When did the first amphibians appear?
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The Carboniferous period.
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On a geologic column, where would you find the oldest rocks?
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Towards the bottom.
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How do scientist determine the absolute ages of rock layers?
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By radio metric dating methods.
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What is the concept of evolution?
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Scientist think the evolution occurs by means of natural selection.
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When did dinosaurs become extinct?
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The end of the Cretaceous period about 65 million years ago.
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During which period did land plants such as ferns begin to develop?
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The Devonian period.
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What can scientist assume about a rock layer that matches a similar layer in a geologic column?
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Rock layers in a geologic column are distinguished by the types of rock the layers are made of and by the kinds of fossils the layers contain.
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Where did the coal deposits found in Pennsylvania, Ohio, and West Virginia come from?
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Coal deposits in Pennsylvania, Ohio, and West Virginia are the fossilized remains of the forests and swamps.
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When did dinosaurs first appear?
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During the Mesozoic Era.
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Describe the conditions on Earth during the Mesozoic Era and the effect these geologic conditions had on plant and animal life.
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Conditions during the Mesozoic Era favored the survival of reptiles.
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Name the periods and epoch into which the Cenozoic Era is divided.
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The Cenozoic Era is divided into two periods: the Tertiary Period and the Quaternary Period and into seven epochs: the Paleocene, Eocene, Oligocene, Miocene, Pliocene, Pleistocene, and Holocene epoch.
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List the eras of geologic time that followed Precambrian time.
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The Paleozoic Era follows Precambrian time.
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List the following units of geologic time in order of relative length, from the longest to shortest: age, eon, period, era, epoch.
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Eon, Era, Period, Epoch, Age
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the geologic era that lasted from 251 million to 65.5 million years ago; also called the Age of Reptiles.
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Mesozoic Era
