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FORCES THAT CHANGE THE EARTH
UNIFORMITARIANISM VS. CATASTROPHISM
CATASTROPHISM
UNIFORMATARIANISM
The same geologic processes that are happening today are the same processes that have been shaping the Earth throughout its history.
This principle was stated by James Hutton about 250 years ago
Before Uniformatarianism, this was the principle that most scientists believed.
A HAPPY MEDIUM
Today, scientists believe that both principles affect our Earth. Although most geological processes occur slowly, Earth does experience sudden geologic events.
A method of determining whether an event or object is younger or older than another event or object.
Measuring the age of an event or object in years.
RELATIVE DATING ABSOLUTE DATING
RADIOMETRIC DATING
THE PRINCIPLE OF SUPERPOSITION
Younger rocks lie above older rocks in undisturbed sequences.
Method of finding out the age of an object by figuring out the ratio of parent material to daughter material.
Okay, don't worry. I am going to explain this.
younger than another object.
LET ME TELL YOU A STORY. THIS IS A STORY ABOUT MR. & MRS. ISOTOPE AND THIER DAUGHTERS. CLICK ON THE VIDEO BELOW TO LEARN MORE ABOUT THIS VERY UNSTABLE FAMILY.
DISTURBANCES IN ROCK LAYERS
RADIOACTIVE DECAY
To determine absolute age, scientists look at the breaking down of an unstable isotope into a stable isotope.
Unconformities are missing rock layers. Usually due to erosion.
Not all rock layers are in nice and neat straight rows. Many have features that cut through them. The principle of crosscutting relations states that geologic features such as faults and intrusions are younger than the rock they cut through.
HALF LIFE
The amount of time it takes for half of the radioactive sample to decay. In other words, the amount of time it takes for half the parent material to decay.
After watching the video on the next screen, I think you will have a better understanding.
ISOTOPES
An atom that has a different number of neutrons than other atoms of the same element.
Most isotopes are stable, but some are unstable. We call them radioactive. These isotopes break down, trying to become stable. This is called radioactive decay. The rate of decay is constant.
The unstable isotope is called the parent isotope. The stable isotope that is produced is the daughter isotope.
FAULT
INTRUSION
EXAMPLE:
I started teaching at EMS after my daughter Alex was born. She is 8 years old. This is relative. You only know that I have worked there less than 8 years.
THE GEOLOGIC COLUMN
DISCONFORMITY
When a rock layer is missing.
Due to:
At some future time deposition begins again.
NONCONFORMITY
Where sedimentary rock layers lie on top of an eroded surface of nonlayered igneous or metamorphic.
Watch the following video. It is an excellent example of unconformities and the 3 main categories.
Like I said before not all rock layers are in nice neat rows. Because of disturbing forces, the disruption in the rock layer sequence can be a challenge for geologists.
ANGULAR UNCONFORMITY
Exists between horizontal rock layers and rock layers that are tilted or folded.
Geologists combine data from all know undisturbed rock sequences from around the world to create an ideal sequence of rock called the GEOLOGIC COLUMN.
Click on the link below to view "What is Relative Dating?"
NOW LET'S PRACTICE FIGURING OUT WHICH LAYERS ARE THE YOUNGEST AND OLDEST. ON A PIECE OF PAPER, PUT THE LAYERS IN ORDER FROM OLDEST TO YOUNGEST.
http://education-portal.com/academy/lesson/what-is-relative-dating-law-of-superposition-principles-of-original-horizontality-cross-cutting-relationships.html
The answers will be on the next section.
Picture #2
Oldest to youngest
C
B
A
D
E
Picture # 1
Oldest to youngest
B
C
D
A
E