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HELUS LifeScience Ch

Life Science Chapter 7: The Age of Earth

Geologists learn about Earth’s history by studying _____. rocks
Scientist ____ _____ realized two processes were at work on Earth—one that forms rock and one that tears it down James Hutton
Hutton developed the principle of _____, which states that the processes at work today are the same processes that have been at work in Earth’s past. uniformitarianism
The ___ ___ is a series of processes that make and change rocks through heating, melting, cooling, uplift, weathering, burial, and increasing pressure. rock cycle
Geologists categorize rocks into three groups based on how the rock ____. formed
The three rock groups are: _____, ____, and ____ igneous metamorphic sedimentary
Igneous rock forms when ____ solidifies. magma
Different types of igneous rocks are identified by the size of the _____ they contain crystals
_____ crystals form from slow cooling Large
___ crystals form from rapid cooling small
____ ____ is any rock subjected to extreme pressure or heat. Metamorphic rock
____ can cause minerals to become more tightly packed. Pressure
Heat can cause minerals to ____ and form a new rock mineral recrystallize
____ ____ form from sediments Sedimentary rocks
____ are tiny particles of eroded rock Sediments
Sedimentary rocks form in a four-step process: ____, ____, ____, and ____. weathering transportation deposition lithification
____ is the physical or chemical breakdown of rock into smaller pieces. Weathering
____ occurs when sediments are moved downhill by running water, wind, movingice, and gravity. Transportation
Individual sediment grains are called ____ clasts
During transportation, clasts become ____ as they wear down and break apart. smaller
As the speed of the sediment carrier slows down, _____-_____ clasts drop out. larger-sized
____ occurs when sediments carried by water, wind, and glaciers stop moving Deposition
The sediments form ____, horizontal layers parallel
____ occurs when sediments become compacted and cementation changes thesediments into rock. Lithification
Layers of rock are called ____ strata
Danish physician ____ ____ presented four principles to help geologists study strata and interpret the rock’s history. Nicolas Steno
The four principles are ____, ____, ____, and ____. superposition original horizontality original lateral continuity crosscutting relationships
The principle of ____ states that in a stack of undisturbed sedimentary rock layers, the layers on the bottom were deposited before the layers on top superposition
The rock layers on the bottom are ____ than the layers farther up. older
____ ____ tells how old something is compared to something else Relative age
The principle of ____ ____ states that rock layers are originally deposited in horizontal, or nearly horizontal, layers. original horizontality
The principle of ____ ____ ____ states that sedimentary rocks form layers that cover large areas. original lateral continuity
The principle of ____ ____ states that a rock layer or feature that cuts across other rock layers is younger than the ones being cut. crosscutting relationships
____ are made up of protons, electrons, and neutrons Atoms
Isotopes of an atom have the same number of protons, but different numbers of ____ neutrons
Isotopes of an element may be stable or ____ unstable
____ ____ occurs when a nucleus gains or loses protons or neutrons Radioactive decay
The gain or loss of protons or neutrons is called ____ radiation
Radioactive decay occurs ____ and at a regular rate automatically
____ decay (an element in all living things) is used in the dating of once-living organisms Carbon
The unstable isotope that decays is called the ____ ____, and the stable atom that forms is called the daughter isotope. parent isotope
____ is the science of comparing annual tree ring growth to date events andchanges in past environments. Dendrochronology
A ____ ____ is a layer of wood cells produced in one year tree ring
Some of the factors affecting the width of tree rings are rainfall, temperature, sunlight, and ____. disease
____ is a technique that gives each tree ring an exact-year date of formation Crossdating
Ernest Rutherford and Frederick Soddy discovered that parent isotopes decay into daughter isotopes at a ____ ____ constant rate
A ____-____ is the amount of time for half of a specific amount of parent isotopes to decay into daughter isotopes half-life
Geologists can determine the ____ ____ of rock by calculating the absolute age of theminerals that compose it. absolute age
The ____ ____ of a mineral is determined by measuring its parent-to-daughter isotoperatio. absolute age
The decay rate of radioactive isotopes is used by geologists as a “____ ____.” natural clock
____ ____ is the procedure used to calculate the ages of rocks and minerals Radiometric dating
____ rocks are most commonly used for radiometric dating Igneous
Determining the age of ____ rocks is difficult metamorphic
Geologists rarely use radiometric dating for ____ rocks sedimentary
The oldest rocks on Earth are part of areas called ____ ____. continental shields
Earth is at least as old as the zircon discovered by geologists in Australia in 2001, which was estimated to be _._ _billion years old. 4.55
Meteorites collected in ____ have been calculated to be between 4.48 and 4.56 billion years old. Antarctica
Rocks from the ____ have been calculated to be approximately 4.6 billion years old Moon
Created by: jnosik