Geologic Time
Relative Dating
Fossil Evidence
Life Through Time
Mass Extinctions
100
What tool do scientists use to organize Earth's 4.6-billion-year history?
The Geologic Time Scale
100
What does relative dating help scientists determine?
Determining if rocks or fossils are older or younger than others without knowing their exact age.
100
What is a fossil?
Preserved remains or traces of ancient organisms.
100
Which appeared first on Earth: dinosaurs or microscopic life?
Microscopic life
100
What does extinction mean?
When every member of a species has died.
200
Approximately how old is Earth?
4.6 billion years old.
200
In undisturbed sedimentary rock layers, where are the oldest layers usually found?
At the bottom.
200
In which type of rock are fossils most commonly found?
Sedimentary rock.
200
During which era did dinosaurs dominate many land ecosystems?
Mesozoic Era.
200
Approximately how many million years ago did non-avian dinosaurs become extinct?
66 million years ago.
300
What are the three eras of the Phanerozoic Eon, from oldest to youngest?
Paleozoic, Mesozoic, and Cenozoic.
300
A rock layer, also known as __________, is visible layer of rock formed during a certain time period.
strata
300
What type of fossil shows evidence of an organism's activity, such as footprints or burrows?
A trace fossil.
300
Which era are we living in today?
Cenozoic Era.
300
What major event contributed to the mass extinction at the end of the Mesozoic Era?
A large asteroid impact.
400
Which is the longest division of geologic time?
An eon.
400
What scientific principle explains why the oldest undisturbed rock layers are usually at the bottom?
The Law of Superposition.
400
What makes an index fossil useful to scientists?
Scientists use index fossils to match rock layers of the same age.
400
During which era did flowering plants evolve and spread widely?
Mesozoic Era
400
What are the names of the Big Five?
500
During which period did Nevada's Basin and Range landscape begin forming through faulting?
Paleogene Period
500
Two rock formations are far apart but contain the same index fossil. What can scientists infer?
The fossil-bearing layers likely formed during approximately the same time interval.
500
Scientists discover marine fossils in rocks high in a mountain range. What does this suggest about the area's past?
The rocks formed in a marine environment.
500
How does the fossil record provide evidence that life has changed over time?
Different fossils appear in rock layers of different ages, showing organisms appeared, changed, and sometimes went extinct.
500
What evidence supports the asteroid-impact explanation for the end-Mesozoic mass extinction? Name two examples.
The Chicxulub impact crater, a worldwide iridium-rich layer, shocked quartz, or impact debris.