Dating Rocks
What type of dating gives the order of events (which rock layer is older or younger) without giving an exact number of years?
Relative dating
Was the Paleozoic Era earlier or later than the Mesozoic Era?
Earlier.
The Mesozoic Era is often called the "Age of" what?
"Age of Reptiles."
Is the Cenozoic Era the most recent era or one of the earliest?
Most recent (current) era.
What is the geologic time scale used for?
To organize Earth’s history into blocks of time based on major events and changes.
Name one law or principle used to determine relative age (for example: younger rocks over older rocks).
Principle of Superposition
Name one major event or life form that first appeared in the Paleozoic
first fish/vertebrates, first land plants, first insects, early amphibians.
Name a major type of animal that dominated the Mesozoic on land.
Dinosaurs
Name one major development in life during the Cenozoic
Mammal diversification, modern birds expanding, grasses spreading.
Put these time units in order from largest to smallest: period, epoch, era.
Era, period, epoch.
What is radiometric dating used to determine: relative age or absolute age?
Absolute age
Which mass extinction ended the Paleozoic Era and allowed new groups to rise afterward?
The Permian mass extinction
What major event at the end of the Mesozoic caused many species (like non-avian dinosaurs) to go extinct?
An asteroid impact and possible volcanic activity
Humans (Homo sapiens) appear in which era?
The Cenozoic Era.
Name one well-known period and state whether it is in the Paleozoic, Mesozoic, or Cenozoic
Example: Jurassic — Mesozoic. (Devonian — Paleozoic; Pliocene — Cenozoic.)
A scientist uses the decay of radioactive isotopes to find a rock’s age in years. What specific term describes this kind of age measurement?
Radioactive/radiometric or Absolute dating
During the Paleozoic, large continental collisions built mountain ranges. What general geologic process causes mountain building when plates collide?
Plate tectonics
The breakup of a supercontinent changed sea levels and climates during the Mesozoic. What was that supercontinent called?
Pangea
Give one way scientists use climate evidence in Cenozoic sediments to learn about past temperatures
Examples: ocean sediment cores showing isotope ratios; pollen in lake sediments indicating vegetation and climate.
Explain the difference between an "epoch" and an "era"
An era is a larger block of time that contains several periods; an epoch is a smaller division within a period.
Explain briefly how fossils help scientists link rock layers between different places
Fossils serve as index fossils or matching fossils; similar fossils in separated layers indicate layers are the same age.
Put these Paleozoic developments in the correct sequence from earliest to latest: land plants, first vertebrates in the sea, insects, formation of large coal swamps.
Example sequence: first vertebrates in the sea → land plants → insects → formation of coal swamps
Explain how changes in the geologic environment during the Mesozoic (one example) helped drive evolution of new groups.
Example: changing sea levels and climates created new habitats, driving evolution of new groups
Describe one major difference between early Cenozoic climates and late Cenozoic climates
Early Cenozoic was generally warmer (greenhouse conditions); later Cenozoic cooled, leading to ice ages.
Give two reasons scientists divide Earth's history into units like eons, eras, periods, and epochs
Examples: (1) To show when major events (like mass extinctions) happened; (2) To help compare rock layers and fossils globally.