unit test study guide Flashcards
Fossil Record
Information about fossils collected by scientists throughout history. It provides evidence about Earth’s history, past environment, and evolution
Absolute Age
The exact age/ number of years since a rock was formed
Relative Age
Determining the age of rocks by comparing them to other rocks
Law of superposition
Used to determine the age of rock layers. It is the sequence of rock layers. The rock layers need to be horizontal and undisturbed.
How to determine the best index fossil?
The best index fossil should be short-lived and widely distributed
Fossils
The preserved remains or traces of living things
How do fossils form?
When an organism dies and is covered in sediment, the sediment slowly hardens and takes the shape of the organism. The remains of the organisms are preserved and the soft parts are eaten by animals. The hard parts become fossils.
Extrusion
Lava that hardens on the surface and forms igneous rock. It is always younger than the rocks below it.
Intrusion
An igneous rock layer formed when magma hardens beneath Earth’s surface
Geologic Time Scale
Important events of the Earth and the evolution of life forms. This is used by geologists to show Earth’s history.
Which Era are we in?
We are in the Cenozoic Era.
Which period are we in? What era has the most periods?
We are in the Quaternary Period. The Paleozoic Era has the most periods
How did scientists decide where the parts of geologic time begin and end?
Because of mass extinction
Why did scientists develop the geologic time scale?
So they could visualize all the important events of the Earth and they could study fossils and rocks throughout the Earth’s time.
What did geologists study in order to develop the geologic time scale
Geologists studied rock layers and fossils to develop the geologic time scale.
