Dating Earth's history
What do rocks record about the past?
Rocks record geologic events and changing life forms.
What is the law of superposition?
It states that in an un-deformed sequence of sedimentary rocks, each bed is older than the one above itnand younger than the one below it.
What is radioactive decay?
It's the release of subatomic particles from the nuclei of radioactive elements util a stable non-radioactive element is produced.
What is absolute dating?
The possibility to obtain numerical dates for events in geologic history.
What is the principle of original horizontality?
It means that layers of sediment are generally deposited in horizontal position.
What is a half life?
It's the amount of time necessary for one half of the nuclei in a sample to decay to its stable isotope.
What does relative dating tell us?
It tells us the sequence in which events occurred, not how long ago they were.
What is the law of cross-cutting relationships?
It states that when a fault cuts through, or when magma intrudes other rocks and crystallizes, we can assume that the fault or intrusion is younger that the rocks affected.
what is the half life of Carbon-14?
5.7 X 103
What is a geologic cross section?
A view of rock layers that are present under the ground.
What are inclusions?
They are pieces of one rock unit that are contained within another.
How much of the original Potassium-40 would you expect to find in a rock that is 1.3 billion years old?
Half or 50%
What is uniformitarianism?
It means that the forces and processes that we observe today have been at work for a very long time and are the same that have occurred during all of Earth's history.
What are index fossils?
Index fossils are widespread geographically, but are limited to a short span of geologic time and occur in large numbers.
What is 49,000,000,000 years in scientific notation?
4.9 X 1010