EARTH
age of earth
billions
what do rocks tell us?
how old the earth is
If I dig up a SIMPLE fossil, what would that fossil's relative age be?
could be older OR younger
superposition
older rocks at the bottom, younger rocks at the top
what does the earliest evidence of life look like in the fossil record?
microbial bacteria
how do we know earths age
rocks & fossils
older rocks are at the ______
bottom
if I dig up a COMPLEX fossil, what would its relative age be?
younger
inclusions
small rocks inside a large rock are older than the big rock
erosion
weathering by wind or water
the _______is key to the _____________
present, past
younger rocks are at the ________
top
How can we tell if a fossil is older than another?
where they are on the rock layers
original horizontality
rock forming layers are in horizontal layers
how do we know if there was a mass extinction?
disappearance of the fossils in the fossil / rock record
uniformitarianism
difference between relative and absolute age
relative: estimate age
absolute: exact age
3 things fossils can give us evidence to
1. relative age
2. types of creatures
3. environment
cross cutting relationships
if one rock feature cuts across another rock, the rock it cuts across is older
which is older? a simple fossil or a complex t-rex dinosaur?
the sequence of past geologic events can be determined by...
In a large rock with a lot of little rocks inside of it, which part of the rock is younger?
larger rock is younger
how do fossils and relative age relate?
lateral continuity
rocks are deposited in large, continuous, sheets in all directions