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Unit 4A Exam Review

Unit 4A: Earth's History Exam Review

What has the study of fossils allowed scientists to do? Describe past environments and the history of life
What are ideal conditions to fossilize remains of an ENTIRE organism? Very rapid burial or freezing
True or False? Footprints and trails are examples of trace fossils. True
How is a petrified fossil formed? When minerals replace parts of an organism
What is the relative age of a rock? It's age compared to the rock layers that surround it
What is the absolute age of a rock It's age in years
How is the absolute age of a rock determined? By radioactive dating
What is a 'half-life' of a radioactive element? The number of years it takes for half of the radioactive element to decay.
On a graph of radioactive decay, how can you determine the element's half life? The half-life is the point on the graph (in years) in which 50% of the radioactive content has decayed
When determining the relative age of rocks, the concept that 'the deeper the rock layer, the older the rock' is known as: The Law of Superposition.
What two things must occur to create an 'unconformity' in rock layers? First, a rock layer is eroded. Second, a new sediment layer is deposited.
The breakdown of an unstable element to form atoms of another element is known as: Radioactive decay.
When did marine invertebrates first appear in the fossil record? During the Cambrian explosion of the Paleozoic era
When did marine vertebrates first appear in the fossil record? During the Ordovician period of the Paleozoic era
When did amphibians first appear in the fossil record? During the Devonian period of the Paleozoic era
Which era is commonly known as 'the age of reptiles' when dinosaurs were common on land? The Mesozoic era
Which era is commonly called 'the age of mammals' when mammals were common on land? The Cenozoic era
Why is the Quaternary period of the Cenozoic era significant? Humans appear in the fossil record.
The record of geologic events and the history of the evolution of life forms as shown in the fossil record is commonly called the: Geologic Time Scale
In a diagram of rock layers, how could you determine which rock layer is the oldest? According to the law of superposition, the deeper the rock layer, the older it is.
In relative aging of rocks, if a boundary between rock layers has been eroded away and a new sediment layer has been deposited on top, what is that called? An unconformity
How is the Geologic Time Scale organized? It is divided into Eons, eras, periods, and epochs.
How/why do geologists use the Geologic Time Scale? Scientist's use the Time Scale to record and keep track of Earth's history.
If the half life of a 20g sample is known to be 24 minutes, How long will it take for only 10g of the sample to remain? 24 minutes
True or False? Geologists divide Earth's long history into smaller units that make up the Geologic Time Scale? True, Geologists have divided Earth's long history into eons, eras, periods, and epochs.
What information in the fossil record helps Geologists determine the boundaries between time periods in the Geologic Time Scale? The appearance or disappearance of species commonly found in the fossil record.
How did Geologists develop the Geological Time Scale? By studying rock layers and index fossils worldwide.
What is an index fossil? A fossil used by geologists for indexing and defining geologic periods
True or False? Earth's atmosphere, oceans, and continents began to form during the first several hundred million years of Precambrian time. True.
Created by: scanto
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