Stratigraphy and Dating Rocks

Multiple Choice

What needs to happen FIRST for a fossil to form?

• A plant or animal must be covered by sediment.

• A plant or animal must die and decompose.

• Sediments fill a a mold to form a cast.

• An earthquake shifts the land up.

Multiple Choice

What needs to happen SECOND for a fossil to form?

• A plant or animal must be covered by sediment.

• A plant or animal must die and decompose.

• Sediments fill a a mold to form a cast.

• An earthquake shifts the land up.

Multiple Choice

What can we infer about animals with dull teeth?

• They ate other animals.

• They ate only plants.

• They ate nothing.

• They only ate fish.

Multiple Choice

What is the correct listing of steps for a fossil?

• 1) Pressure created a rock.

  2) Plant or animal is buried.

  3) Plant or animal is left alone for years.

  4) Plant or animal dies.

• 1) Plant or animal dies.

  2) Plant or animal is left alone for years.

  3) Pressure created a rock.

  4) Plant or animal is buried.

• 1) Plant or animal dies.

  2) Plant or animal is left alone for years.

  3) Plant or animal is buried.

  4) Pressure created a rock.

• 1) Plant or animal dies.

  2) Plant or animal is buried.

  3) Plant or animal is left alone for years.

  4) Pressure created a rock.

Multiple Choice

Where are most fossils formed?

• near volcanoes, because the high heat of the lava helps to form fossils

• in glaciers, because fossils are created when an organism is frozen quickly

• in sedimentary rock, because being buried in sediment helps to form fossils

• near earthquakes, because the shaking ground traps organisms to create fossils

Multiple Choice

The picture shows a tooth fossil of the extinct

Megalodon shark (Black) next to teeth (white) from a great white

shark, which is still found today.

Which of the following best explains the

difference in the size of the teeth?

• Sharks were once larger than the sharks that are living today.

• The fossilized tooth was filled with water, which made it grow in size.

• Sharks alive today do not live long enough to grow very large teeth..

• The fossilized tooth had extra sediment around it, which became a part of it

Open Ended

How do Scientist determine the age of Earth and Fossils that they find ?

Stratigraphy and Dating Rocks

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How Old is the boy in the picture ?

Give reasons for your answer

The Age of Fossils and Rocks can be determined Using 

• The age of fossils can be found by using Relative or Absolute dating .  

• Relative dating compare fossils or found in different areas

• Absolute dating gives rocks an actual date, or date range, in number of years.

• Radioactive dating is used to determine the age of rocks

• Carbon and Argon dating are two types of Radioactive Dating
  

With Absolute Dating there are some elements that are not stable that can change into another element . Scientist look for the new element ( daughter) and see how much of the other ( mother) remains . Half life is the amount of time it takes for half the unstable atom to break down.
Accelerator Mass Spectrometer

Half life for C14 is 5730
Potassium is 1.25 Billion

Absolute Dating

Absolute dating gives rocks an actual date, or date range, in number of years. This is different to relative dating, which only puts geological events in time order.

Multiple Choice

Comparing one object to another in order to determine the approximate age of a rock is termed

• Absolute Dating

• Relative Dating

Multiple Choice

Finding the age of a rock or fossil without comparing it to another is termed

• Relative Dating

• Absolute Dating

Multiple Choice

The length of time required for half of the radioactive atoms in a sample to decay is its...

• era
• age
• half-life
• eon

Multiple Choice

How does absolute age differ from relative age?

• only absolute dating indicates which rock is older than another
• only absolute dating finds the age in years
• only relative dating finds the age in years

Relative Dating

• Relative age does not tell the exact age of an object.

• The relative age of rocks and fossils can be determined using two basic methods: 

• Ordering of Rock 

• Index Fossil

Open Ended

What is a rock ? How are rocks formed ?

Rocks are classified according to the way they are formed:

• Igneous

• Metamorphic

• Sedimentary

Igneous Rocks

Igneous Rocks are formed when melted rocks cool and solidify . Melted rocks when found below the Earth's surface is called magma. Melted rocks which come to the surface are called lava.

Metamorphic Rocks

• Metamorphic rock are formed from either Igneous or sedimentary rocks

• They are formed when the original rock undergo intense heat and pressure

Sedimentary Rocks

• Sedimentary Rocks are formed when sediments are eroded and eventually become deposited.

• Over time different layers are formed .

• The pressure caused by the layers on top caused those below to become solidified into rocks .

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What is the law of Superposition ?

The Law of Superposition states that each rock layer is older than the one above it. 

Multiple Choice

Rocks formed when sediments are eroded and eventually become deposited in layers .

• Igneous

• Sedimentary

• Metamorphic

Law of Superposition

• This law is used to read rock layers. Using this understanding of layering

• Scientists infer that the relative age of the rock or fossil in the rock is older if farther down in the rock layers

• Usually applies to Sedimentary Rock

What is Straigraphy?

• Stratigraphy is the study of the layers of Rocks
• Stratigraphy helps geologist determine when and how each layer was formed
• It gives and indication of age of Earth and organisms

Multiple Choice

Which rock layer is the youngest ?

• A

• B

• C

• D

Multiple Choice

The Law of Superposition helps scientists to determine what?

• The absolute age of rock layers

• The age of fossils

• The relative age of rock layers

• the super powers of squirrels

Multiple Choice

According to the law of superposition, the oldest fossils are found 

• At the top of the rock layers
• Near the bottom of the rock layers
• In the middle of the rock layers
• Somewhat near the surface

Multiple Choice

_{Which rock layer in the diagram seems to be the oldest?}

• F
• E
• B
• A

Multiple Choice

What is the relative age of a rock?

• The age determined by the things around it.

• The age of an igneous rock.

• The age determined by radioactive dating.

• The time it takes for 1/2 of the radioactive atoms to decay in an element.

Multiple Choice

Which of the following orders the rock layers accurately from youngest to oldest?

• 1, 2, 3, 4, 5
• 5, 4, 3, 2, 1
• 2, 3, 4, 5, 1
• 1, 2, 3, 5, 4

What is Unconformity ?

• Over millions of years, tectonic plate motion can distort layers in sedimentary rocks

•  As a result of this, the youngest layers of rock are not always found on top when uplifted

• These layers can become eroded and new deposition takes place .

• Unconformity can give a false impression of the age of the rock.

Open Ended

Why does unconfomity makes it difficult to date rocks?

Intrusive Igneous rock and dating

• Igneous rocks form when lava or magma hardens

• It is intrusive if it cools in between bodies of rock

•   If it cools on the surface it is extrusive.

• An intrusive rock is always younger than the rocks which are around it 

• An extrusive rock is always younger than the rock below it

Multiple Choice

Which rock is the oldest?

• A

• B

• C

• D

• E

Multiple Choice

When a igneous intrusion is found in a layer, what do we know about its age?

• The intrusion is the same age as the rock..

• The intrusion is younger than the rock

• The intrusion is older than the rock

Multiple Choice

Which of the following correctly lists the layers in order from oldest to youngest?

• E, B, C, D, A

• A, B, C, D, E

• E, D, C, B, A

• C, B, A, D, E

Multiple Choice

What letter represent an Intrusive Igneous Rock ?

• A

• B

• C

• D

• E

Multiple Choice

Which rock type is the youngest ?

• Gneiss

• Schist

• Granite

• Shale

Multiple Choice

Comparing one object to another in order to determine the approximate age of a rock is termed

• Absolute Dating

• Relative Dating

What are faults ?

A fault is a break in the rocks that make up the Earth’s crust that is formed due to the movement of rock on either side of the fault. Faults occur where there is movement (a slip) of tectonic plates

Multiple Choice

Which rock layer is the youngest ?

• A

• B

• C

• D

How can faults be used to determine the age of rocks?

• Faults are always younger than the rocks they cut through

• Determining the age of the Fault will give an indication of the rock

Multiple Choice

The arrow is pointing to a(n)

• Igneous Intrusion

• Fault

• Igneous Extrusion

What are Index Fossils ?

Index fossils used to tell the relative age of the rocks in which they are found.

How can Index fossils be used to determine the age of rocks ?

If the age of the fossil can be determined then the age of the rock can be determined relative to the the fossil

What criteria are used to determine if a fossil can be used as an index fossil?

• They must have existed for a very short time  

• Widely distribute

• Easy to identify 

Multiple Choice

Which of the following is incorrect in determining fossil index?

• Easily Identified

• Lived for a very long time

• Lived for a short time

• Widely distributed

Which of the following is an index Fossil?

Multiple Choice

If Fossil A is found in a lower rock layer, and Fossil B is found in an upper rock layer, then Species A most likely _____.

• existed less recently than Species B

• existed more recently than Species B

• evolved into Species B

• evolved from Species B

Multiple Choice

Which of the fossil shown in the diagram would be the index fossil?

• A

• B

• C

• D

Multiple Choice

What is the best reason that fossil #4 is NOT a good index fossil?

• It is not widespread

• it is not short-lived (in numerous layers)

• It is not unique

Multiple Choice

Which fossil would be most useful in determining the relative age for the rocks in these geologic columns?

• Ammonite

• Brachiopod

• Trilobite

• Turritella

Radioactive Dating

• In a process called radioactive decay the atom of one element breaks down to form atoms of another element

• There are 2 types of radioactive dating ; Potassium Argon dating and Carbon 14 dating.

• Radioactive dating does not work on Sedimentary rocks but only Igneous

Carbon 14

• Every living thing has Carbon 14

• When living thing dies the C14 starts to break down

• The time it takes for the C14 to be 50% is called its half life

• C14 takes 5730 years to reach its 1st half life

• At 25% it would 2x5730 =114460 years 2nd half life

• At 12.5 it would be 3 x 5730=17190 years 3rd half life

• At 6.25 it would be 4 x5730 =22920 years 4th half life

• This is constant

Dating older Fossils

• Pottassium 40 is used because it has a longer half life

• The half life of Pottassium would be 1.25 billion years

• 
  

• 
  

• 
  

Multiple Choice

At 70% decay approximately how old will be the age of an organism undergoing C14 radioactive decay?

• 1200

• 5500 years

• 10000

• 12000

Multiple Choice

At 30 % decay approximately how old would an organism undergoing radioactive decay?

• 11000 years

• 20000years

• 5000 years

• 15000 years

Multiple Choice

Which would be used to determine the age of fossil 5billion years old ?

• Carbon14

• Potassium 40

Open Ended

Why would Potassium 40 be used to determine the age of fossils which are older over C14 dating ?