Age Dating Rocks. Two Types of Dating Relative Dating Absolute Dating.
Relative Dating Notes Relative Dating Relative dating is used to arrange geological events, and the...
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Transcript of Relative Dating Notes Relative Dating Relative dating is used to arrange geological events, and the...
Relative DatingNotes
Relative Dating
Relative dating is used to arrange geological events, and the rocks they leave behind, in a sequence. The method of reading the order is called stratigraphy (layers of rock are called strata). Relative dating does not provide actual numerical dates/ages for the rocks.
Relative Age is the “age” of a
rock or strata compared to the ages of other rocks or strata.
Relative Age
Principle of Superposition
as sedimentary rocks form, they are deposited on older rock layers.
Principle of Superposition
in undisturbed layers, the oldest is on the bottom and higher layers are younger.
Principle of Superposition
Oldest layer is on bottom (1)
Principle of Superposition
The Grand Canyon
Principle of Superposition
The Grand Canyon
The law states that layers of sediment
were originally deposited horizontally
under the action of gravity.
Principle of original horizontality
Also known as the principle of faunal succession, is based on the observation that
sedimentary rock strata contain fossilized flora (plants) and fauna (animals), and that
these fossils succeed each other vertically in a specific, reliable order that can be identified
over wide horizontal distances.
Principle of Fossil Succession.
Principle of Cross- Cutting
Relationships An igneous/metamorphic rock, fault, or other geologic feature must be younger than any rock across which it cuts..
Crosscutting Relationships
• Faults • Folds• Intrusions • Extrusions• Unconformities• Nonconformities• Disconformities
Videohttps://
www.youtube.com/watch?v=Dwwk1KdWn9c
Relative Dating: FlashbackFlashback:List the principles of Relative dating that applyto the cross section on the right
Uniformitarianism is the idea that the
processes occurring on earth today are similar to those that occurred in the past.
Uniformitarianism basically says
“The present is the key to the past.”
Uniformitarianism is the idea that
geological features formed slowly over long periods of time.
Uniformitarianism claims the Earth is
4.6 billion years old.
What does the Principle of Superposition say?
1. Sedimentary rocks form in rivers
2. Igneous rocks form faster than sedimentary
3. New rock layers form on top of older ones
4. There are billions of fossils on Earth
Which layer of rock is the
oldest?1. 1
2. 2
3. 3
4. 4
5. They are all the same age
HOW OLD WOULD MOST GEOLOGISTS SAY THE EARTH IS?
1. 6000 years
2. 75,000 years
3. 20 million years
4. 4.6 billion years
According to what theory, is the earth 4.6 billion years old?
1. Catastrophism
2. Uniformitarianism
3. Geologism
4. Agism
Relative DatingNotes
Extrusions are igneous
rock layers that form on the surface when lava hardens.
Extrusions
are always younger than the layers over which they form.
Extrusion
Kubu Rock – Botswana, Africa
Intrusions are igneous
rocks that form when magma pushes up into rock layers.
Intrusions are always
younger than the rock layers they invade.
Intrusion
Intrusion
Intrusion
Devil’s Tower, WY
Intrusion
Devil’s Tower, WY
Stop and Summarize
Stand-up, Hand-up, Pair-up: Create a Venn Diagram with your partner.
In the image below identify as many intrusions and extrusions as
you can!
Faults are breaks in the
earth’s crust. A fault is always younger than the rock it cuts through.
Faults
Faults
Shoshone Fault, CA
Folds occur when
rock layers are compressed together and bend or curve.
Folds
Guadalajara, Spain
Folds
Mojave Desert, CA
Stop and Summarize
Write-Pair-Share: Create a Venn-Diagram comparing Faults and Folds.
Identify the Cross-Cutting
Relationships
1
2 3
Flashback
SOME Relative Dating Practice
Write the correct order of events by numbering their occurrences.
Identify the cross-cut relationships in each cross section.
Relative Dating
Relative Dating
Relative Dating
Relative Dating Example
Unconformities are gaps in the
rock sequence (caused by the erosion of rock layers).
Angular Unconformity occur when rock
layers are tilted or uplifted, and then worn down by erosion and weathering.
Sediments are then deposited on top of these eroded layers.
Angular Unconformity
Angular Unconformity
Disconformities are gaps created
when erosion occurs on an overlying rock layer.
Disconformity
Nonconformity are formed when
sedimentary rock overlays igneous or metamorphic rocks.
Nonconformity
Flashback
E
What type of unconformity is E in the image to the right? List any cross-cutting relationships and order the events from oldest to youngest.
Write a Sequence of event for the following geologic cross-section:
Draw the following geologic cross-section:
1.) 2 layers of sedimentary rock form.
2.) An extrusion forms on top of the two layers.
3.) A 3rd layer of sedimentary rock forms.
4.) An intrusion cuts through all of the rock layers, but not to the surface.
5.) A 4th layer of sedimentary rock forms.
Draw the following geologic cross-section:
1.) 2 layers of sedimentary rock form
2) Layers 1-2 are folded
3.) A 3rd sedimentary layer forms.
4.) A normal fault cuts through all the layers
5.) A 4th sedimentary layer forms.
6.) An intrusion cuts all the way to the surface forming an extrusion.
Top half of paper = Geologic History
Must Include: At least…
• 5 sedimentary rock layers
• 3 different cross-cutting relationships
• 1 disconformity
Bottom half of paper = Geologic Cross Section
• You will draw a geologic cross section numbering the sedimentary layers and lettering cross-cutting relationships. Also identify the type of unconformity.
Correlation is using rock and
fossil evidence to match up dating at different locations.
Correlation
Index Fossils are used for
dating the rock layers in which they are found.
Index Fossils are species that
were abundant all over the earth, but existed for shorter periods of time.
Index Fossil
trilobite
Index Fossil
ammonite
Index Fossil
Correlation using index fossils
Index Fossil
Correlation using index fossils
Exit Slip If humans went extinct in the near
future, would we make good index fossils? Explain your answer!
Hints: use your timescale, and the definition of index fossils.
What kind of cross-cut is shown to the
right?
0%
0%
0%
0% 1. Intrusion
2. Extrusion
3. Folds
4. Unconformity
What kind of cross-cut is
shown to the right?
0%
0%
0%
0% 1. Intrusion
2. Fault
3. Fold
4. Angular Unconformity
What kind of cross-cut is
shown to the right?
0%
0%
0%
0%1. Intrusion
2. Fault
3. Fold
4. Angular Unconformity
0%
0%
0%
0%
What is the name of the type of fossil is used to correlate rock layers at two or more different
locations?1. Mold
2. Petrified fossil
3. Index fossil
4. Trace fossil
0%
0%
0%
0%
Using correlation, Which two layers would you
determine to be of the same age?
1. A & D
2. A & B
3. B & D
4. B & E
Paleontology Notes
READY YOUR REMOTE FOR A QUICK REVIEW
0%
0%
0%
0%
What type of cross-cut appears
at location e?
1. Fault
2. Fold
3. Nonconformity
4. Angular Unconformity
E
0%
0%
0%
0%
What type of cross-cut appears in the
picture?
1. Fault
2. Disconformity
3. Nonconformity
4. Angular Unconformity
Absolute Age is the age in years
of a rock or other object (as determined by radiometric dating.
Radiometric Dating
entails finding the amount of certain radioactive elements left in a rock or object.
Journal
TURN TO YOUR JOURNAL PAGE
Journal #5
Draw a geologic cross-section with the following:
1.) At least 3 sedimentary rock layers
2.) At least 3 cross-cuts
(faults, folds, intrusions, extrusions, or unconformities,
angular unconformities, nonconformity, disconformity)
Write a geologic history that explains the order of occurrence of each event.
Paleontology Notes
READY YOUR REMOTE FOR A QUICK REVIEW
0%
0%
0%
0%
Which of the following is
oldest?
1. Sandstone B
2. Sandstone A
3. Earthquake fault
4. Igneous Dike B
0%
0%
0%
0%
What type of cross-cut appears
at location e?1. Fault
2. Fold
3. Nonconformity
4. Angular Unconformity
E
0%
0%
0%
0%
What type of cross-cut appears in the
picture?
1. Fault
2. Disconformity
3. Nonconformity
4. Angular Unconformity
- Albert Einstein
“The important thing is to never stop questioning.”
How much do you know about Paleontology?
Pre-Unit Questions
(Post-Unit)
Answer the following True/False Questions
How much do you know about Paleontology?
Pre-Unit Questions
(Post-Unit)
Answer the following True/False Questions
Many scientists theorize that dinosaurs were wiped out
many years ago by some great catastrophe.
0%
0% 1. True
2. False
How much do you know about Paleontology?
TRUE. Obviously dinosaurs don’t exist today and they seem to disappear suddenly from the
fossil record.
Fossils take millions of years to form.
0%
0% 1. True
2. False
How much do you know about Paleontology?
TRUE or FALSE?
FALSE. Fossils can form in less than a year depending on the
conditions.
There are billions of fossils found all over the earth.
0%
0% 1. True
2. False
How much do you know about Paleontology?
TRUE. There are many fossils buried in the rock all over the planet. Over 99% of them are
small marine plants and animals.
Dinosaurs are “giant lizards.”
0%
0% 1. True
2. False
How much do you know about Paleontology?
FALSE. Some were large, but many were not. The term
dinosaur, coined in the 1800’s, does mean “terrible lizard,” but the
average size of a dinosaur was that of a large dog.
JOURNAL # 6
Describe & discuss at least three new facts
that you learned about paleontology while studying this
unit.
RETURN YOUR REMOTEClasswork Assignments
1.) Journal # 6
2.) Relative Dating Geologic Cross-Sections WS
3.) Paleontology Test Review
Partner Assignment
1.) Draw a geologic Cross-Section on a blank piece of
paper
2.) Include at least 5 sedimentary layers & 3 cross-cuts (intrusions, extrusions,
faults, folds, or unconformities)
3.) Swap with a friend & have him/her number the events