fossils
age of rocks
radioactive dating
the geologic time scale
a trip through geologic time
100
this is a slim coating of carbon on rock
What is carbon film
100

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100
radioactive dating can only be used with this kind of rock
What is igneous rock
100
one of the three long units of geologic time between precambrian and the present
What is an era
100
this era is called the age of the reptiles
What is the mesozoic era
200
this is a kind of fossil that means turning to stone
What is a petrified fossil
200
what is a gap in the geologic record
What is unconformity
200
this half the time for an atom to decay
What is a half-life
200
eras that are subdivided into units of gelogic time
What is periods
200
during this Era jawless fish evolved
What is the paleozoic era
300
this a hollow area in sediment in the shape of an organism
What is a mold
300
what is lava that hardens on the surface
What is an extrusion
300
near which kind of rock can radioactive dating test the intrusions and extrusions around it
What is sedimentary rock
300
animals that lived during the palezoic era without backbones
What is an invertabrate
300
2.5 billion years ago organisms first used this to make food
What is the sun
400
this is a kind of fossil that provides evidence of the activities of ancient organisms
What is a trace fossil
400
what is magma that cools and hardens into a mass of igneous rock
What is intrusion
400
when an unstable atom breaks down it releases this
What is energy and particles
400
what are the basic units of geologic time
What is eras, periods, and epochs
400
this period is when human ancestors first evolved
What is the quaternary period
500
this layer of rock is produced from sediments
What is sedimentary rock
500
the age compared to the ages of other rocks
What is relative age
500
matter is made up of this kind of element
What are atoms
500
what is a record of the life forms and gelogic events in history
What is the geologic time scale
500
this was Earth's first geologic time period
What is precambrian time
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