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Sci Chapter 8 and 9

Scientists believe that the Earth is ____ years old 4.6 billion
The principle that geologic processes that occurred in the past can be explained by current geologic processes is called Uniformitarianism
These layers of rock show the sequence of events that took place in the past Strata
The most commonly studied type of rock layer is sedimentary
The boundary between two beds of rock is called a bedding plate
The principle that a sedimentary rock layer is older than the one above it is called the law of superposition
The principle that a fault or intrusion is younger than the layers it cuts through is called the law of crosscutting relationships
The absolute age of a rock layer is its ______ age. numeric
Using the rate of ______ to determine absolute age would be less accurate for a surface feature such as the Grand Canyon which is millions of years old erosion
In general, about 30 cm of sedimentary rock are _____ over a period of 1,000 years. deposited
Some sedimentary rock layers show annual layers called varves
Which layer (summer or winter) is composed of darker, finer grains? winter
Atoms of the same element that have different numbers of neutrons are called isotopes
The original radioactive isotope is called the _____ isotope. parent
The half-life is the time required for half of a radioactive sample to break down by decay to form the _____ isotope. daughter
The ages of wood, bones, shells and other organic remains embedded in rock can be determined through (carbon) radiometric dating
The scientific study of fossils is called paleontology
Some insects become fossilized in hardened tree sap called amber
Organisms buried in _____ do not decay, because bacteria do not survive such low temperatures. ice
When minerals in groundwater percolate through buried organic matter, the result is a nearly perfect mineral replica of the object. This process is called ______. (Hint: it often happens to wood) petrification
A fossil residue of a leaf that makes a "shadow" on sedimentary rock is called a carbon film
Fossilized dung or waste is from an animal is called a copriolite
The stones from the digestive tracts of dinosaurs are called gastroliths
Fossilized tracks, borings or burrows are called ____ fossils. trace
Fossils that occur only in rock layers of a particular geologic age are called ____ fossils. = index
Geologists use index fossils to locate deposits of oil and natural gas
What does the geologic time scale do? Divides Earth's history into time intervals
Scientists are able to determine the absolute ages of most rock layers in a geologic column by using radiometric dating
To determine the age of a specific rock, scientists might correlate it with a layer in a geologic column that has the same relative position and fossil content
Geologic periods can be divided into epochs
Precambrian time ended about ______ years ago. 542 million
The most common fossils in Precambrian rock are cynaobacteria
The first vertebrates appeared during the Paleozoic Era
The Age of Reptiles is the name commonly given to the Mesozoic Era
The first flowering plants appeared during the Cretaceous Period
The Age of Mammals is the name commonly given to the Cenozoic Period
Created by: Jayson Van Dam