Do Now HW due Friday 9/30

Transcription

1 Do Now HW due Friday 9/30 1. Describe the process of formation of a sedimentary rock. 2. Draw out the rock cycle clearly state how each rock type becomes another rock type. 3. Make a chart and compare & contrast metamorphic and igneous rock.

2 Fossils and The Law of Superposition By L. Badino, Truman Middle School Adapted from Liz LaRosa 5 th Grade Science This PPT was created with the information from the FOSREC Activity Who s on First? and Fossil Inferences by UEN.

3 Fossils A fossil is the preserved remains of a once-living organism most commonly preserved in sedimentary rock Start at 1:21 min --

4 What We See

5 What Scientists See Fossils are not found like assembled dinosaurs you see in museums.

6 Types of Fossils

7 Index Fossil Most Important!!! What is an index fossil? A fossil that is used to establish the age of the rock layers. It is found in the rock layers of only one geologic age. It is found in rock layers around the world. ex Trilobites

8 Using Fossils to Date Rocks Scientists have found that particular types of fossils appear in certain layers of rock If a certain organism only existed for a short period of time, its fossils would show up in a certain layers of rock. Index Fossils are fossils of organisms that lived during a relatively short time period. Trilobites are the most known index fossil. Any rock layer containing a trilobite fossil is thought to be about 400 million years old

9 Trace Fossils Trace fossils show the activities of organisms. An animal makes a footprint when it steps in sand or mud. FANCY FOOTWORK This dinosaur footprint was found in Namibia, Africa. Over time the footprint is buried in layers of sediment. Then, the sediment becomes solid rock.

10 Molds MOLD FOSSIL This mold, or imprint, is of an extinct mollusk called an ammonite. A mold forms when hard parts of an organism are buried in sediment, such as sand, silt, or clay. The hard parts completely dissolve over time, leaving behind a hollow area with the organism s shape.

11 Casts CAST FOSSIL This ammonite cast was discovered in the United Kingdom. A cast forms as the result of a mold. Water with dissolved minerals and sediment fills the mold s empty spaces. Minerals and sediment that are left in the mold make a cast. A cast is the opposite of its mold.

12 What do fossils tell us? Fossils give clues about organisms that lived long ago. They help to show that evolution has occurred. They also provide evidence about how Earth s surface has changed over time. Fossils help scientists understand what past environments may have been like.

13 Check for Understanding 1. What is a fossil? 2. What are the different types of fossils? Explain each type. 3. If you found a PALM LEAF in ANTARCTICA what would that tell you about Antarctica?

14 Do Now HW due Friday 9/30 1. What is a fossil? 2. What are the different types of fossils? 3. What can fossils tell/reveal about earth s past? 4. If you found a snake fossil at the bottom of a river, what might that mean about that area?

15 How are fossils formed? 1. Sediment An animal is buried by sediment, such as volcanic ash or silt, shortly after it dies. Its bones are protected from rotting by the layer of sediment. 2. Layers More sediment layers accumulate above the animal s remains, and minerals, such as silica (a compound of silicon and oxygen), slowly replace the calcium phosphate in the bones. 3. Movement Movement of tectonic plates, or giant rock slabs that make up Earth s surface, lifts up the sediments and pushes the fossil closer to the surface. 4. Erosion Erosion from rain, rivers, and wind wears away the remaining rock layers. Eventually, erosion or people digging for fossils will expose the preserved remains.

16 How are fossils formed? What important information about fossils can you get from these two videos? JU 3/quicktime/l_043_01.html

17 Check for Understanding 1. How are fossils formed? List the steps and explain each one. 2. What can fossils tell us about the area that they were found in?

18 The Law of Superposition Oldest rocks are at the bottom, newest rocks are at the top! The layers are arranged in horizontal layers (original horizontality) of sedimentary rock, each layer is older than the layer above it and younger than the layer below it.

19 Relative Dating: Which one came first? When we discuss the age of rocks, we classify them as either absolute or relative. The relative age of a rock is its age compared to the ages of other rocks. Very General The sedimentary rock was older than the metamorphic rock The absolute age of a rock is the number of years since the rock formed. Very Specific The sedimentary rock is 450 year old.

20 Relative & Absolute Dating Activity Put the children in order from oldest to youngest. Classify each statement as relative or absolute. 1. Anthony is the youngest 2. Emily is 4 years old 3. Michael is older than Sherry 4. Sherry is 16 years old 5. Ashley is older than Emily but younger than Sherry

21 Superposition Suppose that you have an older sibling who takes a lot of pictures of your family and piles then into a box. Over the years they keep adding new photos to the top of the stack. Think about the family history recorded in those photos. Where are the oldest photos the ones taken when you were a baby? Where are the most recent photos those taken last week?

22 Superposition Just like sedimentary rock, as you move from top to bottom, the layers become older. The principle that states that younger rocks lie above older rocks in an undisturbed sequence is called superposition

23 Check for Understanding

24 Extinction??... Oh no! The death of every member of a species is called extinction. List some animals that are extinct. BrainPop: Extinction

25 Exit Ticket

26 Do Now HW due Friday 10/2 1. What are fossils? (give the correct definition) 2. What type of rock are fossils found in? 3. How are fossils formed? List the steps and explain each one. 4. What information can fossils give us about the earth & the environment? 5. What is the difference between absolute and relative age? 6. What is an index fossil? List an example of an index fossil

27 Activity # 1 Obtain Set A materials: 8 index cards or slips of paper with letters on them. Each slip of paper represents a rock layer. Each letter represents a kind of fossil. Your task is to determine what the correct sequence of the letters are, from oldest to youngest.

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29 Method: 1. The card with the letters T and C is on the bottom, or the oldest layer. 2. Look for a card that has either a T or C written on it for the second layer. Since this card has a common letter with the first card, it must go on top of the first card. This second layer is younger than the TC layer.

30 3. Sequence the remaining cards using the same process. Note Sometimes organisms disappear or become extinct. Extinction is forever - once an organism disappears from the sequence it cannot reappear later

31 Answer This is the sequence of life on the planet

32 Questions for Activity 1: 1. Neatly list the layers in order, with the oldest on the bottom and the youngest at the top. Label as such on the side of your listing. 2. Explain why M is the same age as D in the layer DM. 3. Explain why D in rock layer OXD is older than the D in rock layer DM. 4. Which letter(s) showed up the most? 5. Which letter(s) showed up only once? 6. What could have happened to the organisms represented by the letters that disappeared? 7. Which letter(s) could be index fossils? Explain why you made this choice.

33 Activity # 2 Obtain Set B materials: 8 index cards or slips of paper with fossils on them. Each slip of paper represents a rock layer. Your task is to determine the correct sequence of the letters, from oldest to youngest. The oldest layer has the letter M in it. Use the same method that you used in Activity # 1.

34 M S A G I N R O

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36 Questions for Activity #2: 1. Neatly list the layers in order, with the oldest on the bottom and the youngest at the top. Label as such on the side of your listing. 2. Explain why a pelicypod and an ammonite are the same relative age. 3. Which is older a crinoid or a horn coral? Why? 4. Which fossils could be used as index fossils? Explain why - how is an index fossil is different than just any fossil?

37 Questions for Activity 2: 5. What kind of rocks would you find fossils in? 6. Explain how this activity illustrates the Law of Superposition and Relative Age Dating? 7. Compare these fossil images to the real fossils provided to you. Describe.

38 What Did You Learn? 1. How does the Law of Superposition help us determine the relative age of rock layers? 2. How do fossils help us determine the relative age of rock layers? 3. What two characteristics must a fossil have to be considered an index fossil?

39 Exit Ticket

40 Extra Info Slides

41 What is a fossil? A fossil is the preserved remains of a onceliving organism. What do fossils tell us? Fossils give clues about organisms that lived long ago. They help to show that evolution has occurred. They also provide evidence about how Earth s surface has changed over time. Fossils help scientists understand what past environments may have been like.

42 HOW IS A FOSSIL FORMED? 1. Sediment An animal is buried by sediment, such as volcanic ash or silt, shortly after it dies. Its bones are protected from rotting by the layer of sediment. 2. Layers More sediment layers accumulate above the animal s remains, and minerals, such as silica (a compound of silicon and oxygen), slowly replace the calcium phosphate in the bones. 3. Movement Movement of tectonic plates, or giant rock slabs that make up Earth s surface, lifts up the sediments and pushes the fossil closer to the surface. 4. Erosion Erosion from rain, rivers, and wind wears away the remaining rock layers. Eventually, erosion or people digging for fossils will expose the preserved remains.

43 FIVE MAIN TYPES OF FOSSILS Petrified Fossils Molds and Casts Trace Fossils Carbon Films Preserved Remains

44 PETRIFIED FOSSILS The word petrified means turning into stone. Petrified fossils form when minerals replace all or part of an organism. PETRIFIED FOSSIL The Field Museum in Chicago displays a fossil of a Tyrannosaurus rex. Water is full of dissolved minerals. It seeps through the layers of sediment to reach the dead organism. When the water evaporates, only the hardened minerals are left behind.

45 MOLDS AND CASTS A mold forms when hard parts of an organism are buried in sediment, such as sand, silt, or clay. MOLD FOSSIL This mold, or imprint, is of an extinct mollusk called an ammonite. The hard parts completely dissolve over time, leaving behind a hollow area with the organism s shape. A cast forms as the result of a mold. Water with dissolved minerals and sediment fills the mold s empty spaces. CAST FOSSIL This ammonite cast was discovered in the United Kingdom. Minerals and sediment that are left in the mold make a cast. A cast is the opposite of its mold.

46 CARBON FILMS All living things contain an element called carbon. When an organism dies and is buried in sediment, the materials that make up the organism break down. FERN FOSSIL This carbon-film fossil of a fern is more than 300 million years old. Eventually, only carbon remains. The thin layer of carbon left behind can show an organism s delicate parts, like leaves on a plant.

47 TRACE FOSSILS Trace fossils show the activities of organisms. An animal makes a footprint when it steps in sand or mud. FANCY FOOTWORK This dinosaur footprint was found in Namibia, Africa. Over time the footprint is buried in layers of sediment. Then, the sediment becomes solid rock.

48 PRESERVED REMAINS Some organisms get preserved in or close to their original states. Here are some ways that can happen. Amber An organism, such as an insect, is trapped in a tree s sticky resin and dies. More resin covers it, sealing the insect inside. It hardens into amber. Tar An organism, such as a mammoth, is trapped in a tar pit and dies. The tar soaks into its bones and stops the bones from decaying. Ice An organism, such as a woolly mammoth, dies in a very cold region. Its body is frozen in ice, which preserves the organism even its hair!