Name: ____________________________

FOSSILS• What is a fossil?

____________________________________________________________________________________________________________________________________________________________

• Fossils are most often found in ______________ rock. • Sometimes fossils are found in other materials, such as ______________,

______________ or ______________.• Fossils are NEVER found in ______________ or ______________ rock.

FOSSIL FORMATION• A fossil forms over ______________ of years. Here’s how:

1. When an organism dies, Its body falls to the ______________. If in a body of water, its body sinks to ______________.

2. ______________, such as sand, silt or clay ______________ the dead organism. The sediment forms ______________, which turn to ______________.

3. The dead organism is ______________ in rock. The ______________, or at least the ______________ parts of the organism usually ______________, leaving behind an ______________ or fossil.

4. Over time, the rock ______________ or wears away. This ______________ the fossil, which can be observed and studied by scientists. Sometimes scientists ______________ up rock to look for fossils.

STUDYING FOSSILS• We can determine what organisms lived more ______________ compared to

organisms that lived long ago depending on the rock ______________ fossils are found in.

• Fossils in ______________ or shallow layers of rock are ______________ than fossils in ______________ layers of rock. Therefore, we can assume the organisms that formed these fossil lived more ______________ than organisms that formed fossils found in ______________ layers.

• Fossils found in the ______________ layer of rock often indicate organisms that lived at the ______________ time.

• Scientists can ______________ determine how old fossils are. Fossils found in superficial rock layers are ______________ than fossils found in ______________ rock layers.

• Identify the youngest and oldest fossil in the rock layers below.

© Stephanie Elkowitz

• Scientists can also ______________ determine how old fossils by measuring certain ______________ in the fossils and/or rocks the fossils are found in.

• Fossils can help scientists determine what the ______________ was like in the past. For example:– If fossils of ______________ organisms are found in a location that is now

______________ land, that area must have been covered by the ______________ at some point in the past.

– If fossils of ______________ plants are found in a location that is now covered by ______________, that area was ______________ land at some point in the past.

• What are 5 different types of fossils?1. ____________________________ 2. ____________________________3. ____________________________4. ____________________________5. ____________________________

• Describe the different types of fossils in the table below.Type of Fossil Description

Mold Fossil

Cast Fossil

Trace Fossil

© Stephanie Elkowitz

True Fossil

Petrified Fossil

INDEX FOSSILS• What is an index fossil?

____________________________________________________________________________________________________________________________________________________________

• Index fossils have two characteristics that make them helpful in dating other fossils:– Index fossils are ______________ ______________, found in many

______________ regions of the world.– Index fossils are ______________ in ______________ ______________. They

are only found during a relatively ______________ time frame because the once-living organism only ______________ during a short time frame.

• When an unknown fossil is found in the ______________ layer as an index fossil, scientists can infer that the unknown fossil is from the ______________ time period as the index fossil.

• If an unknown fossil is found in a layer of rock with ______________ index fossils from different but ______________ time periods, the unknown fossil must have lived during the ______________ time period.

• Index fossils are also helpful in determining ______________ fossils or ______________ of rock in different locations.

• Sometimes rock layers and fossils within them ______________. • Sometimes fossils do not ______________. • Index fossils help “______________” layers of rocks in different ______________

when this happens.• Common Index Fossils:

© Stephanie Elkowitz

RELATIVE DATING• What is relative dating?

____________________________________________________________________________________________________________________________________________________________

• Relative dating does not determine the ______________ age of a rock layer. It determines the relative age of one rock layer in ______________ to other rock layers. In other words, it determines which layer of rock is ______________, ______________, ______________, etc.

• What are four important rules that help scientists date layers of rock?1. ____________________________ 2. ____________________________3. ____________________________4. ____________________________

Law of Superposition• According to the Law of Superposition, sedimentary rock layers are laid down

on top of each other. The ______________ is the oldest and the ______________ is the youngest.

• In order for the rock layer to form, a layer of rock must have ______________ below it. Therefore, ______________ or deeper layers are always ______________ than ______________ or shallower layers.

© Stephanie Elkowitz

Principle of Original Horizontality • The Principle of Original Horizontality states that sediment is deposited

______________ or in “flat rows.” • Sediment is deposited on the surface of Earth. Over time, sediment

______________ and compacts to form ______________ rock. Sediment is deposited this way due to ______________.

Cross-Cutting Relationships • ______________ exist in some layers of rock and can create fractures. The

fractures can cause layers of rock to ______________ or ______________.• Cross-cutting relationships is a principle that states that a ______________ or

fracture through rock layers must be ______________ than the layers through which it cuts through. A fault cannot cut through rock if the rock did not previously ______________.

Intrusive Relationships • Sometimes ______________ from within Earth slowly pushes up through rock in

Earth’s crust. The magma ______________ and forms ______________ rock. We call this an ______________ ______________.

• Intrusive relationships states that an ______________ intrusion is ______________ than the layers of rock through which it “______________” or cuts through.

Relative Dating & Erosion• Sometimes geologic processes, such as ______________, can alter the

______________ and ______________ of rock layers. • ______________ can cause all or part of a rock layer to ______________ away.

This can happen when a ______________ pushes rock layers or when ______________ water erodes away layers of rock.

• What are the relative ages of the different layers of rock? Number them 1 through 5, with 1 being the oldest and 5 being the youngest.

© Stephanie Elkowitz

ABSOLUTE DATING

© Stephanie Elkowitz

• Scientists have the ability to determine the age of rocks and fossils with a method called ______________ or ______________ dating.

• When this process involves ______________, we call this method ______________ dating.

• ______________ is an important compound in the environment. It combines with other ______________ to form substances important to the ______________ and substances that make up ______________ things.

• A very small percentage of carbon is ______________. This carbon is called ______________. ______________ carbon is unstable. Over time, it breaks down or ______________ to become ______________, releasing ______________ or excess ______________.

• A living thing takes in ______________ from the environment, including ______________ carbon. It uses and ______________ the carbon in its body. When the organism ______________, it stops taking in carbon. The carbon in its body ______________ until it decomposes. If it becomes a ______________, the carbon remains in the ______________.

• Radioactive carbon is also found in ______________. When the rock forms, some of the carbon is ______________.

• Carbon-14 breaks decays at a specific rate. We call this rate the ______________.

• What is a half-life? ____________________________________________________________________________________________________________________________________________________________

• Carbon-14 has a half-life of ______________ years.• This means that 100 gram of carbon-14 will take ______________ to decay to

_____ grams of carbon-14. The other _____ gram becomes a stable decay product (specifically, Nitrogen).

• After a second half life, ______________ of the 50 grams of Carbon-14 becomes stable. Therefore, _____ grams of the original sample is Carbon-14 and the remaining _____ grams is Nitrogen.

• Scientists study the ______________ of carbon-14 to its decay ______________ in fossils to determine how old a fossil is.

• Studying this ratio helps scientists calculate how many ______________ the fossil or rock has been through.

• This half-life of carbon-14 is a long time but just right for radioactive dating fossils that are less than ______________ years old.

• Scientists can use other radioactive elements found in living things and rocks to date objects that are ______________ than ______________ years old.

EARTH’S PAST CLIMATE• Scientists are interested in what Earth was like in the ______________. They

want to understand what the ______________ was like and what life forms dominated the planet.

• They also want to know about ______________ that may have altered ______________ and ______________ on Earth.

• ______________ can give us an idea about what an environment was like, but they cannot tell us about the ______________ in Earth.

© Stephanie Elkowitz

• What are two ways scientists study Earth’s past climate?– ____________________________ – ____________________________

TREE RINGS• Scientists can get an idea of what climate was like in a ______________ place

by studying ______________ ______________. • Tree rings are ______________ rings that form on trees. • If you look at a cross section of a tree trunk, you will see ______________.• There are 2 different colored rings:

1. ______________ colored rings represent wood growth during the ______________. This wood is less dense and thus lighter in color. We often call this growth “______________ growth.”

2. ______________ colored rings represent wood growth during the ______________. This wood is more dense and thus, darker in color. We call this growth “______________ growth.”

• One light and dark colored ring represents ______________ ______________ of growth.

• Scientists can take a sample from a tree and study the tree rings. This sample is called a ______________ ______________.

• A ______________ core shows ______________, which represent the tree ______________. Scientists study the ______________ of the bands to make ______________ about past climate where the tree grew.

• The ______________ of a ring represents the amount of ______________ that took place during a season. – A ______________ tree ring represents a ______________ growing season.

A long growing season often occurs when temperatures are ______________ and precipitation is ______________.

– A ______________ tree ring represents a ______________ growing season. A short growing season often occurs when temperatures are ______________ and precipitation is ______________.

• If scientists know that every pair of rings represents one ______________, scientists can study what ______________ and ______________ may have been like each year where the tree grew.

• In some places, scientists can study tree rings from ______________ of years ago.

• Scientists can study tree rings from ______________ trees as well as ______________ wood (such as petrified wood).

• What are two major limitations to studying tree rings?1. _______________________________________________________________________

_________________________________________________________________________

2. ________________________________________________________________________________________________________________________________________________

© Stephanie Elkowitz

• Scientists can decrease limitations by studying ______________ trees from an area and comparing the tree ______________ of the ______________ trees. They look for ______________ in the tree cores to make more ______________ predictions.

ICE CORES• Scientists can study what Earth’s ______________ was like long ago by

studying the composition of ______________ at the polar ice caps.• The ice sheets of the polar ice caps form from incremental buildup of

______________. Snow forms ______________ of ______________, in the same way that sediments form layers of sedimentary rock.

• ______________ layers of ice are found ______________ younger layers of ice. • When the snow falls and forms layers of ice, bubbles of ______________,

______________ and other particles are trapped in the ice. • Scientists are interested in the particles ______________ in the ice because

they give insight into Earth’s ______________ during the year in which each ice layer formed.

• Scientists study the ______________ of these particles in the layers of ice. They do this by ______________ into the ice and extracting large ______________ of ice.

• We call the extractions ______________ ______________. • An ice core shows ______________, which correspond to layers of ice. Each

year, ______________ layers of ice form:– The first layer forms when ______________ falls and ______________ and

______________ are trapped in the snow. This layer forms during ______________.

– The second layer form when part of the first layer ______________ during the ______________. Gas bubbles are ______________ and so this band appears as “______________ ice” in an ice core We call this the ______________ ______________.

• Scientists date the ______________ of ice. They do this by studying their ______________ in the core and/or with ______________ dating.

• The polar ice caps are made of many layers of ______________. The oldest layers of ice at the polar ice caps are more than ______________ years old.

• Scientists analyze the ______________ trapped in the layers of ice. They are most interested in levels of ______________ ______________ and ______________ particles. – Carbon dioxide is associated with average global ______________. – Dust particles are associated with ______________ ______________.

• Scientists analyze the ______________ of the layers. © Stephanie Elkowitz

– The thickness of a ______________ layer can be used to determine the amount of ______________ during that year.

– ______________ layers are related to summer ______________. ______________ melt layers indicate ______________ summer temperatures.

• From these findings, scientists make ______________ about Earth’s ______________ and its ______________, relative ______________ and precipitation.

• Scientists make these predictions because they believe the information they obtain about conditions at the ______________ ice caps can be extrapolated to make predictions about Earth’s ______________ conditions.

• Scientists believe that large amounts of ______________ trapped in an ice core can indicate high levels of ______________ activity on Earth.

• During a volcanic eruption, large amounts of ______________ and ______________ are released into the atmosphere. Dust and ash ______________ all over the Earth with wind currents, and settle in different places on the globe.

• Scientists observe a ______________ relationship between amount of ______________ ______________ in an ice core and ______________ (determined by the melt layer).

• Many scientists believe that ______________ levels of carbon dioxide in the atmosphere is the ______________ of ______________ temperatures.

Reflection Questions

1. What characteristics do all living things have in common? ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

2. Why do you think genetics is most important in classifying organisms? ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

3. Draw a diagram to show ALL the domains, kingdoms, phyla and classes you learned about. ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

4. Why is it important that we classifying organisms in a systematic and organized way? ________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________________

© Stephanie Elkowitz