Absolute Dating
The time for a radioactive isotope to decay by half.
What is a half-life?
The name of the epoch where humans were first around.
A fossil that is useful for finding the relative ages of rock layers.
What is an index fossil?
The geologic law that states that the rock layer at the bottom of the oldest.
What is the Law of Superposition?
The geologic event that (likely) led to the extinction of the dinosaurs?
What is a meteorite or asteroid?
A radioactive isotope with a half life of 4.5*10^9 years.
What is Uranium-238?
This is what created the oxygen in Earth's atmosphere around 2 billion years ago.
What is cyanobacteria?
A group of fossils on the Reference Table that became extinct at the end of the Devonian period.
What are Placoderm Fish?
An intrusion is this type of rock.
What is igneous?
This rock type is represented by bricks on the reference tables.
The percentage of Rubidium-87 that remains after 2 half lives.
What is 25%?
The mountain-building event that occurred in New York State during the Ordovician period.
What is the Taconian Orogeny?
The geologic period with the earliest mammals.
What is the Triassic?
This geologic event must have occurred if rock layers are no longer horizontal and are now bent.
What is folding?
The name of the oldest fossils found in the rock record.
What are stromatolites?
A radioactive isotope that CANNOT be used to age a fossil or rock older than 1 billion years old.
What is Carbon-14?
The cause of carbon dioxide gas in Earth's early atmosphere.
What is volcanoes?
The fossil group that includes Valcouroceras.
What are Nautoloids?
This represents a gap in the geologic record. It's also called erosion.
What is an unconformity?
This is the estimated amount of money spent by Americans every year on Valentine's Day.
(The group with the closest estimate gets a point!)
What is 19.6 billion dollars?
The amount of time that has passed if 12.5% of Carbon-14 is measured in a sample.
The end of this ERA is associated with a mass extinction of many land and marine animals, including trilobites.
What is the Paleozoic?
A city in New York where you would most likely find a Cooksonia fossil in the bedrock.
(HINT: You should use pages 3, 8, and 9 of the reference tables!)
What is Niagara Falls or Syracuse?
This is a small igneous intrusion that CUTS THROUGH rock layers.
What is a dike?
These popular Valentine's Day candies were originally created as medical lozenges.
What are candy hearts?