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