17.1- The Rock Record Flashcards
1
Q
Fossils
A
The remains, traces, or imprints of ancient organisms and often found embedded in rocks
2
Q
Geologic Time Scale
A
record of earth’s history from its origin 4.6 b years ago to present day
3
Q
4 categories of the geologic time scale
A
eons, eras, periods, and epochs
4
Q
eon
A
longest time unit in the geologic scale
5
Q
precambrian
A
informal unit of geologic time consisting of the first three eons during which earth formed and became habitable
6
Q
era
A
second longest time unit
measured in 10s to 100s of millions of years
7
Q
period
A
3rd longest time period
8
Q
4 units of eon time period (oldest to youngest)
A
Hadean, Archean, proterozoic, phanerozic
9
Q
the 3 earliest _______ make up ______ percent of geologic time
A
eons, 90
10
Q
3 eras
A
paleozoic, mesozoic, cenozoic
