Fossils
Evidence of past life preserved in rock.
What are fossils?
The principle stating that deeper rock layers are older than layers above them.
What is the Law of Superposition?
Earth is about this many years old.
What is about 4.6 billion years?
The extinction event that wiped out the dinosaurs.
What is the mass extinction at the end of the Mesozoic?
Scientists use this method to compare rock layers and determine which is older.
What is relative dating?
Fossils usually form in this type of rock.
What is sedimentary rock?
When magma cuts through existing rock layers it forms this.
What is an intrusion?
The timeline scientists use to organize Earth’s history.
What is the geologic time scale?
Plants first moved onto land during this era.
What is the Paleozoic Era?
This method uses radioactive elements to determine the actual age of rocks.
What is radiometric dating?
Fossils that lived for a short time but were widespread are called these fossils.
What are index fossils?
A break in the rock record caused by erosion or missing layers.
What is an unconformity?
The oldest and longest part of Earth’s history.
What is the Precambrian?
The first simple life forms appeared during this time.
What is the Precambrian?
The breakdown of radioactive elements over time is called this.
What is radioactive decay?
The preserved remains or traces of organisms such as footprints or burrows.
What are trace fossils?
Rock layers that form from sediments pressed and cemented together.
What is sedimentary rock?
The era known as the “Age of Dinosaurs.”
What is the Mesozoic Era?
A sudden event where many species disappear from Earth.
What is a mass extinction?
The time it takes for half of a radioactive element to decay.
What is half-life?
Scientists study fossils to learn about organisms and this from the past.
What are past environments?
Scientists study rock layers to determine this about Earth’s past.
What is the relative age of rocks?
The era we currently live in where mammals dominate.
What is the Cenozoic Era?
Scientists believe this space object may have caused the dinosaur extinction.
What is an asteroid?
Scientists combine fossils and rock data to build this timeline.
What is the geologic time scale?