5th Science (Thick Book)

The following notes are for those students who are working out of the Harcourt "thick" book. Refer to pages C22-25 “How Earth’s Surface Has Changed”.
Vocabulary

The students used a vocabulary strategy to define the following words. Each strategy included the word, definition, sentence, additional facts, and a picture;

• Continental Drift:
  • Definition: a theory of how earth's continents move over its surface
  • Sentence: The surface of earth is constantly changing because of continental drift.
  • Additional Facts: continental drift continues today
• Pangea:
  • Definition: a supercontinent containing all of earth's land that existed about 225 million years ago
  • Sentence: Evidence suggests that about 200 million years ago, Pangea broke into two big continents.
  • Additional Facts: Pangea broke into Gondwana and Laurasia
• Fossil:
  • Definition: the remains or traces of past life found in sedimentary rock
  • Sentence: The sedimentary rocks of the Grand Canyon contain a fossil record of organisms from earth's earliest history.
  • Additional Facts: fossils show how earth has changed

Continental Drift (page C22):

• continental drift = changes to earth’s surface
• the surface of earth has changed and will continue to change
• continental drift is very slow
• the fossil record serves is evidence of continental drift

The Rock Record of the Grand Canyon (page C23):

• contains sedimentary rock nearly 2 billion years old
• sedimentary rock forms from sediments that have cemented together
• slice of earth's history
  • the position of sedimentary rock layers, scientists can infer the relative ages of the rocks
  • younger rock layers are found on top of the older rock layers
  • some of the oldest rock layers on earth are near the bottom of the Grand Canyon
  • the walls of the Grand Canyon contain rock from only the earliest stages of earth's history
  • erosion has worn away the most recent rock
  • the canyon's north rim contains rock that is about 250 million years old
• cuts through 20 different layers of sediment
• contains a fossil record of organisms from earth's earliest history
• processes that made the Grand Canyon are still occurring today;
  • running water still erodes sedimentary rock layers
  • new layers of sedimentary rock are still forming

How Fossils Show Changes (page C24):
· fossils show;
o that life on earth has not always been the same
o types of organism that lived on earth
o earth’s surface was different;
§ scientist have found fossils or sea organism in rock at the top of high mountains
§ they infer that those areas were once under water
o evidence of continental drift;
§ fossils of similar plants and animals have been found in Africa, South America, India, and Australia
§ this means that these continents were joined at one time
· most fossils are traces or imprints of dead plants and animals
o when a organism dies it is buried in sediment
o a mold or cast is made as the sediment hardens into rock
o a mold forms when underground water dissolves the organism
· some fossils are the entire organism frozen in ice and fossilized bones and teeth

Review Questions:
1. What did Earth’s surface look like 225 million years ago?

2. What happened to the supercontinent?

3. What will happen to the continents in the future?

4. What evidence was there to support the theory of continental drift?

5. Why can’t you see direct evidence of continental drift?

6. When looking at the Grand Canyon where are the most recently formed fossils?

7. When looking at the Grand Canyon where are the rocks located from the time of Pangea?

Red Check Questions & Answers:

Page C22: What is the theory of continental drift?

updated: 12/6 at 9:15 am