Other Chapters' Lyrics:
Earth Science 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10 - 11 -:- Life Science 1 - 2 - 3 - 3b - 4 - 4b - 5 - 6 - 7 - 8 - 9 - 10 - 11 - 12 -:- Physical Science 3
Earth Science 1 - 2 - 3 - 4 - 5 - 6 - 7 - 8 - 9 - 10 - 11 -:- Life Science 1 - 2 - 3 - 3b - 4 - 4b - 5 - 6 - 7 - 8 - 9 - 10 - 11 - 12 -:- Physical Science 3
Back to the full science song list. -:- Download free mp3 of this song. -:- Composer's home page.
_______________________________________________________________________________________
Earth Science
Chapter 6 - Summary Notes
á
Geologists use relative dating to
determine whether an object or event is older or younger than other objects or
events.
á
One way they do this is with the
principle of superposition. This
states that younger rocks lie above older rocks.
á
Scientists use the geologic column,
which is an ideal sequence of all dated rock layers, as a standard for dating
rocks.
á
When rock layers donÕt match the
geologic column, it is called unconformity. Missing layers can be caused by erosion, or they were never
deposited in the first place.
á
Unlike relative dating, absolute
dating determines the actual number of years an object has existed. Radiometric dating is the most common
method of absolute dating.
á
Isotopes are atoms of an element that
have different numbers of neutrons.
Some are unstable and tend to decay. Radiometric dating calculates age based on the decay of
isotopes in an object.
á
Evidence of life is preserved in
fossils. Fossils form in various
ways.
á
In permineralization, an organismÕs
tissue pores is filled with minerals.
Petrified wood is an example.
á
Insects sometimes get stuck in tree
sap, which then hardens to preserve the insect in amber.
á
Some of the best fossils are those of
animals frozen so quickly that their bodies never decompose, like the wooly
mammoth.
á
Fossils tell us what the earth was
like in the past. Marine fossils
are often found on mountaintops, which means that the rocks were pushed up from
sea level in ancient times.
á
Index fossils are fossils with known
ages. These fossils tell us the
age of rock found nearby.
á
The geologic time scale divides the
EarthÕs 4.6-billion-year history.
It is divided into eons, which are divided into eras, then periods, then
epochs.