Rock Dating Methods
This type of age tells which rock is older or younger, not the exact number of years.
What is relative age?
This law states that in undisturbed rock layers, the oldest layer is on the bottom.
What is the law of superposition?
A timeline that organizes Earth’s history into eras and periods.
What is the geologic time scale?
The era when life became more complex and Pangaea formed.
What is the Paleozoic Era?
The first type of life on Earth.
What are single-celled organisms?
This type of age tells the exact age of a rock in years.
What is absolute age?
A crack in rock where movement occurs and layers shift.
What is a fault?
Scientists divide the geologic time scale into these large sections.
What are eras and periods?
The era known as the “Age of Dinosaurs” and Pangaea broke apart.
What is the Mesozoic Era?
Plants like ferns first became abundant during this time.
What is the Paleozoic Era?
This radioactive element is used to date younger rocks and fossils.
What is carbon-14?
Magma pushing into rock layers and hardening is called this.
What is igneous intrusion?
The time that covers about 88% of Earth’s history.
What is Precambrian time?
The era when mammals became the dominant land animals and continents moved to their current positions.
What is the Cenozoic Era?
Reptiles dominated Earth during this time.
What is the Mesozoic Era?
The time it takes for half of a radioactive substance to decay is called this.
What is half-life?
Lava flowing onto Earth’s surface and forming new rock layers is called this.
What is extrusion?
The main purpose of the geologic time scale.
What is to organize and sequence events in Earth’s history?
This event happened early in the Paleozoic and caused many new organisms to appear.
What is the Cambrian explosion?
Flowering plants appeared after this group became dominant.
What are reptiles (dinosaurs)?
The scientific method used to determine the absolute age of rocks using radioactive elements.
What is radioactive dating?
When rock layers are worn away and moved by wind or water, this process has occurred.
What is erosion?
Why very few fossils exist from Precambrian time.
What is most fossils were destroyed over time?
Two reasons the Cambrian explosion may have happened.
What are more resources and more organisms?
Humans appeared during this era.
What is the Cenozoic Era?