Geologic Time
What makes a good index fossil?
widely distributed but limited
what is the law of superposition?
oldest layers on the bottom and the youngest layers on top
What is a half life?
The time it takes for 1/2 a parent element ro decay to a daughter element
WHat period do we leave in ?
Quaternary
what is the difference between relative and absolute time?
relative is based on position and absolute gives an exact age in years
What is the law of Cross-cutting Relationships?
a fault or intrusion is younger than the rock layer it crosses
how do you determine a half life?
use radio active decay
What are the 4 eras of geologic time? which lasted the longest? which lasted the least amount of time?
Precambrian, Paleozoic, Mesozoic, Cenozoic; Precambrian was the longest era; Cenozoic lasted the least amount of time
How old is the earth?
4.6 billion years old
What is the law of original horizontality
Rock layers are originally deposited horizontally
What types of material can you use it on?
you can use it on fossils or sedimentary structures
When did the dinosaurs first appear?
Mesozoic era; Triassic period
as you move through the geologic time scale, what happens to the animals and organisms?
the animals become more advanced and diverse
What is an unconformity? what are the different types of unconformities?
A disruption is deposition; non-conformity, angular conformity, disconformity
what is the half life scale?
1/2 = 1 half life
1/4= 2 half lives
1/8= 3 half lives
When did the greatest extinction occur? what is the most widely accepted theory for the extinction?
end of the Cretaceous; a giant meteor/ asteroid impact
What was Pangaea? During what geologic period did it form?
When all of the continents were joined into 1 super continent; It formed into the paleozoic era - permian period
how do you calculate the age of a fossil?
# of half-lives x the half- life rate of that parent element
what is the geologic time scale?
an outline of the development of the earth and the life on the earth and of life on the earth