Fossils
What 2 things are key to increase the likelihood of an organism becoming a fossil?
Hard parts and quick burial
The age of a rock layer compared with the age of another rock layer is an example of
Relative Dating
What does an unconformity indicate?
A period of erosion, or at least no deposition.
What is the shortest of the 4 ways time is measured on a geologic time scale?
Epoch
Who came up with the idea of Uniformitarianism?
James Hutton
What are fossils?
Pieces or remains of organic things (plants, animals...)
which principle states that sedimentary beds originate as continuous layers that extend in all directions?
Explain the law of superposition and why it's important
it states that older layers of rock will be at the bottom and younger layers will be on top as long as the rock layers haven't been disturbed. It's important because it provides an order for determining the relative ages of rock layers.
What is Willard F. Libby famous for?
He came up with radiocarbon dating
What organisms were dominant during the "Era of Reptiles" known as the Mesozoic ERA?
Dinosaurs
What type of fossil is rare but can completely preserve the organism?
Amber
What the difference between absolute and relative dating?
Absolute dating gives a year or range of years that something lived in.
Relative dating gives a sequence of time, what comes first, then next. A comparison
Why is the principle of cross-cutting relationships, especially when it involves igneous intrusions, critical for adding more dating accuracy to relative dating
Igneous intrusions can be numerically dated, so can give a more accurate idea of the time period of the sedimentary layers
How old is the earth?
4.5 billion years old
Why are the periods of geologic time all different lengths?
the time scale was developed using fossil succession with no reference to absolute time, so random units of time resulted
How do you make fossil dating more accurate?
Combine it with other dating methods
If there is 6.25% of parent isotope left, how many half lives have passed
4
Is an intrusion older or younger than the layer below it?
younger
What is the era we live in?
Cenozoic
List 2 pros and 1 con of relative dating
can determine the general age of sedimentary rock
can show the sequence of events
Con:
Can't give exact date of formation
What is an index fossil?
A fossil of an organism that only existed for a short period of time.
This type of absolute dating in measures how much a radioactive element has decayed, and uses this rate of decay to determine how much time has elapsed since that fossil was alive or since that rock layer was laid down.
Radiometric Dating, absolute dating of rocks
if you saw an angular unconformity, what would you guess has happened
Uplift and tilting of the sedimentary layers, followed by erosion prior to a new period of deposition
List the categories of geologic time in the correct order from greatest to least span of time
Eon, era, period, epoch
List 1 pro and 2 cons of absolute or radiometric dating
Pro:
Can determine the exact date of formation of igneous and metamorphic rock
Con:
can't be used on sedimentary rock
only accurate when the mineral is in a closed system