1. Riverwood Middle School 8th Grade Science McAven
Rocks and Fossils
Riverwood Middle School
8th Grade Science
McAven
Blue is the color of the day

2. Types of Rocks Igneous - formed when molten rock cools.
Sedimentary – formed by the “cementing together” of small grains of sediment.
Metamorphic – rocks changed by the effect of heat and pressure.

3. Igneous Rocks rocks formed by the cooling of molten rock (magma.)
volcano
Magma cools and solidifies forming igneous rocks

4. Igneous Rocks
When molten rock cools, forming what are called igneous rocks, radioactive atoms are trapped inside.
Afterwards, they decay at a predictable rate. By measuring the quantity of unstable atoms left in a rock and comparing it to the quantity of stable daughter atoms in the rock, scientists can estimate the amount of time that has passed since that rock formed.
Absolute geologic dating and relative geologic dating are two methods by which scientists try to determine the age of geologic evidence.
Carbon-14 dating is an example of absolute dating, and the law of superposition is an example of relative dating.

5. Sedimentary Rocks
Getting older
Sedimentary Rocks are formed when particles of sediment build up and are “cemented together” by the effect of pressure and minerals.
sea
Fragments washed to the sea
Sedimentary
rocks
Rocks are broken
up by the action
of weather

6. Sedimentary rocks are:
Sedimentary rock makes up about 75% of the rocks on the Earth’s surface.
Sedimentary rocks are:
the only type of rocks that contain fossils.
Fossils give us a great deal of information.
Fossils tell us about the environment when the sediments were deposited. 
Sedimentary rocks form on the surface of the Earth, anywhere that sand, mud, or other types of sediment collect.
Sedimentary rock layers can be disturbed by igneous rock. This happens when molten rock forces it way up through the layers above it. This forms igneous rock sections within and across the sedimentary layers.
The sedimentary rock layers must be there first, therefore the igneous rock intrusions are younger than the layers it cuts through. Sometime the molten rock will force its way to the surface and erupt, creating a younger igneous layer at the surface.
With time, more sedimentary layers can form on top of the igneous rock. Igneous rock is always younger than rock layers it cuts through.

7. Metamorphic Rocks heat
Metamorphic rocks are formed by the effect of heat and pressure on existing rocks.
This can greatly affect the hardness, texture or layer patterns of the rocks.
Magma
Pressure from surface rocks
metamorphic
rock
forming
here
heat

8. Here’s the 3 kinds of rock & how they form
Fossils are found in only 1 kind
– Which one?
– Explain?
Igneous & metamorphic are too hot - fossil remains incinerate
Sedimentary rock - only

9. How do fossils form? Fossils are usually found in sedimentary rock.
Sedimentary rock is the type of rock that is made of hardened sediment.

10. How do fossils form?
Most fossils form when living things die and are buried by sediments.
The sediments slowly harden into rock and preserve the shapes of the organisms.

11. How do fossils form?
Fossils are the preserved remains or traces of living things.
Fossils provide evidence of how life has changed over time.
Fossils also help scientists infer how Earth’s surface has changed.
Fossils are clues to what past environments were like.

12. Scientists who study fossils are called paleontologists.

13. What are the different kinds of fossils?
Preserved
fossils
Rock Fossils
amber
tar
ice
Trace fossils
Casts and
molds
Petrified
Carbon films

14. Chapter 8 Research Read CH. 8 Section 1: pages 318 – 324
Add one fact to each fossil type on your concept map.

15. mold
– forms when sediments bury an organism and the sediments change into rock; the organism decays leaving a cavity in the shape of the organism.
Cast
forms when a mold is filled with sand or mud that hardens into the shape of the organism
Petrified
(permineralized fossil) – forms when minerals soak into the buried remains, replacing the remains, and changing them into rock.

16. preserved
forms when entire organisms or parts of organisms are prevented from decaying by being trapped in rock, ice, tar, or amber.
carbonized
forms when organisms or parts, are pressed between layers of soft mud or clay that hardens squeezing almost all the decaying organism away leaving the carbon imprint in the rock.
trace
forms when the mud or sand hardens to stone where a footprint, trail, or burrow of an organism was left behind.

17. What are the different kinds of fossils?
Fossils found in rock include petrified fossils, molds and casts, carbon films, and trace fossils.
Other fossils form when the remains of organisms are preserved in substances such as tar, amber, or ice.

18. What are the different kinds of fossils?
Trace fossils
Trace fossils provide evidence of the activities of ancient organisms.
A fossilized footprint is on example of a trace fossil.
Other examples of trace fossils include the trails that animals followed or the burrows that they lived in.

19. Stomach Stones

20. What are the different kinds of fossils?
Molds and casts
A mold is a hollow area in sediment in the shape of an organism or part of an organism.
A mold forms when the hard part of the organism such as a shell, is buried in sediment.
A cast is a copy of the shape of an organism.
Water carrying dissolved minerals and sediment may seep into the empty space of a mold. If the water deposits the minerals and sediment there, the result is a cast.

21. What are the different kinds of fossils?
Petrified Fossils
A fossil may form when the remains of an organism become petrified.
Petrified means “turning to stone”
Petrified fossils are fossils in which minerals replace all or part of an organism.

22. What are the different kinds of fossils?
Carbon films
An extremely thin coating of carbon on rock.
HOW DOES A CARBON FILM FORM?
When sediment buries an organism, some of the materials that make up the organism can become gases. These gases escape from the sediment, leaving carbon behind. Eventually, only a thin film of carbon remains.

23. What are the different kinds of fossils?
Preserved Remains
Some processes preserve the remains of organisms with little or no change.

24. Amber Ancient organisms also have been preserved in amber.
Amber is the hardened resin, or sap, of evergreen trees.

25. TAR Some remains are preserved when organisms become trapped in tar.
A dark, thick, flammable liquid distilled from wood or coal, consisting of a mixture of hydrocarbons, resins, alcohols, and other compounds. It is used in road making and for coating and preserving timber.

26. Tar Heel
Tar Heel is a nickname applied to the U.S. state of North Carolina and its inhabitants. It is also the nickname of the University of North Carolina athletic teams, students, alumni, and fans.
The exact etymology of the nickname is unknown, but most folklore believe its roots come from the fact that tar, pitch, and turpentine created from the vast pineforests were some of North Carolina's most important exports early in the state's history. For a time after the American Civil War, the name Tar Heel was derogatory, but it was later reappropriated by the people of North Carolina. Because the exact history of the term is unknown, a number of legends have developed to explain it. One such legend claims it to be a nickname given during the U.S. Civil War, because of the state's importance on the Confederate side, and the fact that the troops "stuck to their ranks like they had tar on their heels". The term "Tar Heel" gained popularity during the Civil War.
-Wikipedia

27. Ice Cores
Cylinders of ice that are drilled out of glaciers and polar ice sheets that help scientists know more about past climates.
When snow falls it carries with it the compounds that are in the air at the time. In areas where temperatures are rarely above freezing (ice sheets and glacial areas), this builds up layer upon layer of compacted snow which becomes ice. Within these ice layers there is a record of the atmosphere at the time that the snow creating the ice layers fell.

29. Ice cores contain an abundance of information about climate.
temperature
ocean volume
precipitation
atmospheric chemistry
volcanic activity
Sunlight variation
forest fires
Ice cores contain an abundance of information about climate.

30. Match with Video Mosquito in DNA:
Dinosaur Tracks in Texas:
La Brea Tar Pit
Tree Rings
Ice Core:
Videos to use as supplement:
Land Before Time Footprint:
Ice Age Cave Art:
Ice Age Ice:
Croods TAR:
Flag Freezing:
Dino DNA:

31. What do fossils tell about how organisms have changed over time?
The fossil record provides evidence about the history of life on Earth. The fossil record also shows that different groups of organisms have changed over time.
The fossil record reveals a surprising fact: fossils occur in a particular order.
Older rocks contain fossils of simpler organisms. Younger rocks contain fossils of more complex organisms.
In other words, the fossil record shows that life on Earth has evolved, or changed.

32. What do fossils tell about how organisms have changed over time?
Paleontologists use fossils to build up a picture of Earth’s environments in the past.
Fossils also provide evidence of Earth’s climate in the past.
Scientists can use fossils to learn about changes in Earth’s surface.

33. INDEX FOSSIL
EASILY IDENTIFIABLE
SHORT-LIVED
WIDESPREAD OCCURRENCE

34. Index Fossils
To be an index fossil –an organism must have lived only during a short part of Earth’s history.
Many fossils of the organism must be found in rock layers.
The fossil must be found over a wide area of Earth; the organism must be unique.

35. Index Fossils
The shorter time period a species lived, the better an index it is.
A key example of an organism used as an index fossil are trilobites, a group of hard-shelled animals whose body had three sections, lived in shallow seas, and became extinct about 245 million years ago.
Therefore, if a trilobite is found in a particular rock layer, it can be compared with trilobites from other layers to estimate the age of the layer in which it was found.

36. In Summary
Most fossils form when living things die and are quickly buried by sediment, which eventually hardens and preserves parts of the organisms.
The major kinds of fossils include petrified remains, molds, casts, carbon films, trace fossils, and preserved remains.
The fossil record shows that many different organisms have lived on Earth at different times and that groups of organisms have changed over time.

37. Bill Nye: Fossils