If the Earth's entire 4.5-billion-year history is represented by my arm span, human existence is the size of...
A fingernail shaving
Why was it necessary for plants to be present before animals could survive?
Oxygen, food
What generally happened at the end of each era of Earth's history?
A mass extinction event
The age of one thing in comparison to another is called...
Relative age
How old something actually is in years is known as...
Absolute age
The Law of ________ says that older layers of rock are always found below younger layers of rock.
Superposition
The Law of ________ says that if a fault or intrusion cuts through another body of rock, then it must be younger than the rock it cuts through.
Cross-Cutting Relationships
This method of dating rocks, which calculates a rock’s age in years by measuring the amount of radioactive isotopes, is only useful for igneous rocks.
Radioactive dating
Which rock layer came first: R, X, B, or F?
X
Which is the youngest rock layer in the picture?
H
The animal this fossil belongs to is a...
Giant prehistoric sloth
Index fossils belong to organisms that lived in a ________ area for a ________ amount of time.
Large area, short amount of time
Most major groups of animals first appeared in the fossil record during the...
Cambrian Explosion
An animal with a backbone is called a...
Vertebrate
Dying out or extermination of a species is called...
Extinction
Which eon of Earth's history has no fossils?
Hadean Eon
