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a view of earth's pa
section one
| Question | Answer |
|---|---|
| Where can we find evidence of changes in conditions on Earth's surface? | in the rock layers of the Earth's crust |
| What do scientists use to describe the sequence of length of changes in Earth's crust? | geologic time scale |
| What is the purpose of the geologic time scale? | This scale outlines the development of Earth and life on Earth |
| What two things did 19th century scientists do to determine the relative ages of sedimentary rock all over the world? | 1. studying fossils 2. applying the principle that old layers of rock are below young layers |
| Why did scientists combine their observations of rocks all over the world? | Because no single area on Earth contained a record of all geologic time |
| The ordered arrangement of rock layers is called? | geologic column |
| A geologic column represents a ________ of Earth's history. | timeline |
| 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 | geologic column (official definition) |
| In a geologic column, the oldest rocks are located at the _______ of the column | bottom |
| What two things distinguish a rock layer in a geologic column? | 1. types of rock the layers are made of 2.the types of fossils the layers contain |
| How do the fossils in the upper layers of a geologic column differ from those in the lower, older layers? | Fossils in upper most recent layers resemble modern plants and animals while lower, older layers contain fossils of plants and animals different from those of today |
| Many of the fossils that have been discovered in the oldest layers of rock have been ______ for millions of years. | extinct |
| When the first geologic columns were developed, what factors did scientists use to estimate the ages of rock layers? | the average rate of sediment deposition |
| What method has enabled scientists to determine the ages of rock layers more accurately? | radiometric dating methods |
| Suppose a scientist wants to determine the age of a rock layer with a geologic column. With what does the scientist compare the rock layer? | with a similar layer in a geologic column that contains the same fossils or that has the same relative position |
| Suppose a layer of rock matches a layer on the geologic column. What does this tell a scientist | that these layers likely formed at about the same time |
| What three indicators do geologists use to divide the geologic time scale into smaller units? | 1. major changes in the Earth's surface 2. climate 3. types of organisms |
| How are rocks grouped within each unit of geologic time similar? | similar fossils |
| A unit of geologic time is usually characterized by _________ of a dominant life form. | fossils |
| What does the abbreviation Ma stand for? | mega-annum |
| What does mega-annum mean? | million years |
| When did Precambrian time begin? | 4.6 billion years ago |
| The largest unit of geologic time is an _____ | eon |
| Geologic time is divided into how many eons | 4 |
| List the 4 eons | 1. Hadean Eon 2.Archean Eon 3. Proterozoic Eon 4. Phanerozoic Eon |
| The first three eons of Earth's History (Hadean, Archean, and Proterozoic) are part of a time interval commonly known as ________ _______ | Precambrian time |
| The precambrian time lasts about how long | 4 billion years |
| True or False the Precambrian time contains most of earth's history? | true |
| True or False Very few fossils exist in Precambrian rocks. | True |
| Why is dividing Precambrian into smaller time units difficult? | because very few fossils exist to help scientists separate things into smaller time periods |
| Going from largest to smallest list the time periods | Eons, Eras, Periods, Epochs, Ages |
| Define era | a unit of geologic time that includes two or more periods |
| Define Period | a unit of geographical time that is longer than an epoch but shorter than an era |
| Define epoch | a subdivision of geologic time that is longer than an age but shorter than a period |
| An epoch may be divided into smaller units of time called _______ | ages |
| Precambian time includes what 3 eons | Hadean, Archean, Proterozoic |
| After the precambian time, what eon began? | Phanerozoic |
| Eons are divided into smaller units of geological time called | eras |
| What is the 1st era of the phanerozoic eon? | Paleozoic Era |
| How long did the Paleozoic Era last | about 291 million years |
| Paleozoic rocks contain fossils of a wide variety of ______ and _______ life-forms. | marine and terrestrial |
| What era begins after the Paleozoic Era? | Mesozoic |
| What were the Mesozoic fossils like? | early forms of birds and reptiles like the giant crocodilian (see picture in book) |
| How long did the mesozoic era last | 186 million years |
| The present (current) geologic era is called the | cenozoic era |
| When did the cenozoic era begin | about 65 millions years ago |
| Fossils of ________ are common in the Cenozoic rocks. | mammals |
| Eras are divided into shorter time units called _________ | periods |
| Each period is charaterized by what | specific fossils |
| Each period is is usually named for what | the location in which the fossils were first discovered |
| A period can be divided further into units called ______ | epochs |
| What does the scientist have to have in order to divide periods into epochs? | a rock record that is least deformed and a detailed fossil record |
| An epoch can be divided further into what units | ages |
Created by:
kellyaem