Vocabulary
Determining Ages of Rocks
Geologic Time Scale
Major Events in Earth's History
Periods
100
This is a rock's age compared to the ages of other rocks.
What is relative age?
100
Geologists use this to determine the relative ages of sedimentary rock layers
What is the law of superposition?
100
Eras are subdivided into units of geologic time called these
What are periods?
100
An animal with a backbone
What is a vertebrate?
100
Dinosaurs with bird-like features appeared in this famous period, which is the namesake of well-known books and movies.
What is the Jurassic period?
200
This is a record of the geologic events & the evolution of life forms, as shown in the rock & fossil records
What is the geologic time scale?
200
The preserved remains of traces of living things are called these
What are fossils?
200
The Mesozoic era is defined by the dominance of these
What are dinosaurs?
200
An animal that lives part of its life on land & part of its life in water
What is an amphibian?
200
This period started the Mesozoic era, and featured both the first mammals and dinosaurs.
What is the Triassic period?
300
Animals without backbones
What are invertebrates?
300
A gap in the geologic record
What is an unconformity?
300
Scientists constantly refine the geologic time scale for this reason.
What is the discovery of new data?
300
These have scaly skin & lay eggs that have tough, leathery shells
What are reptiles?
300
This period came just after the end of Precambrian time, along with an "explosion" of new life forms.
What is the Cambrian period?
400
This is the number of years that have passed since the rock formed.
What is absolute age?
400
The rock layers at Location 4 differ from those of the other three locations. This natural process of removing rock layers likely occurred between layers A and C at Location 4.
What is erosion?
400
This is an example of physical evidence used to organize Earth's history on the geologic time scale
What are fossils?
400
An event during which many types of living things became extinct at the same time
What is a mass extinction?
400
This period featured the appearance of flowering plants—also bees!
What is the Cretaceous period?
500
Geologists divide the time between the Precambrian & the present into these 3 long units of time.
What are eras?
500
The rock feature is a break and movement in the Earth's crust.
What is a fault?
500
These are te remains of organisms that were widely distributed but existed for a relatively short amount of time.
What are index fossils?
500
A vertebrate that controls its own body temperature & feeds milk to its young
What is a mammal?
500
This period in the Paleozoic era—well before the "Age of Reptiles"—is also known as "The Age of Fish".
What is the Devonian period?