4.13 Mountains to Rock (pg. 222-223)
Understanding Concepts: Read pages 222 & 223. Then answer the following questions:
1) What part does erosion play in the formation of sedimentary rock?
Erosion brings the sediment downriver to a place where it can settle and begin to form the layers of sediment that will eventually harden into rock.
2) Explain why there are different types of sedimentary rocks.
Different types of sediment will form different types of sedimentary rock; for example, clay and silt sediment will form share, while sand sediment will form sandstone rock.
3) In a series of diagrams, show what eventually causes sedimentary layers to become hard.
The enormous pressure of the layers above will eventually cause sedimentary layers to form rock.
4) The Niagara Gorge is being created by erosion caused by the Niagara River. What will happen to the rock eroded by the river?
The rock eroded by the Niagara River will eventually settle as sediment where the river empties into Lake Ontario (SKIP)
5) In many parts the world, including North America, there are areas of sedimentary rock that extend for hundreds of kilometres. What does this clue tell you about the ancient history of these areas?
Sedimentary rock deposits that extend for hundreds of kilometres indicate that erosive forces continue to work and that the mouth of a river, for example, continues to move upstream. (SKIP)
6) The oldest rock in the world is about 4 billions years old, almost as old as Earth itself. However, this rock is not sedimentary. Speculate on how this rock might have formed.
It might have been pushed up from beneath the Earth�s crust, or formed when volcanic lava cooled.
4.14 Fossils: Rock�s Timekeepers (pg. 224-225)
Understanding Concepts: Read pages 224 & 225. Then answer the following questions:
1) What are fossils and how are they made?
Fossils are impressions or mineralized replacements of living organisms that have bones or shells and that have been buried before they can be decomposed?
2) Why are fossils rare?
Fossils are rare because the living organisms must have either bones or a shell, and have been buried before decomposition can occur.
3) Based on what you have learned, why would scientists who have only fossil evidence have to be careful about interpreting what life was like on Earth?
Fossil evidence provides information only about those organisms that lived on Earth and had bones or shells. Fossils evidence would tell scientists nothing about other organisms that did not have bones and/or shells.
4.15 Drifting Continents (pg. 226-227)
Understanding Concepts: Read pages 226 & 227. Then answer the following questions:
1) Describe the theory of plate tectonics.
The theory of plate tectonics states that the Earth�s crust was once a supercontinent that has since broken up into landmasses that have gradually moved apart to where they are now.
2) What clues are there that continental drift has been occurring for millions of years?
Clues include the shape of the continent, that they appear to have once fit together like puzzle parts, living organisms on two landmasses that might have at one time been attached are similar in many ways.
3) A large deposit of gold is discovered on the west coast of Africa. According to the theory of plate tectonics, where else in the world might a similar deposit be found? Use a map to support your opinion.
A similar deposit might be found on the east coast of South America(assuming that Africa and South America were once joined together). (SKIP)
4.16 Moving Plates (pg. 228-229)
Understanding Concepts: Read pages 228 & 229. Then answer the following questions:
1) What are plates?
Plates are large, solid sections of the Earth�s crust that move slowly, or float, on the liquid mantle underneath.
2) Describe what happens when two plates meet and when two plates move apart.
When two plates meet, one usually slides under the other, where it pushes into the mantle, heats up, and melts. When two plates move apart, hot magma from the mantle rises up into the crack between the separating plates, and cools, forming new ridges of rock.
3) Look at figure 1. Why might Vancouver have more earthquakes than Toronto or Halifax?
Toronto and Halifax sit roughly over the middle of a large plate (little activity associated with this location), while Vancouver sits over a position where two plates are colliding, but not moving. At some point, something has to give, and when it does, there will likely be an earthquake. (SKIP)
4) Where on the Earth would you expect to find young, newly formed rock? Where would you expect to find old rock? Explain.
Young, newly formed rock would be found anywhere where magma, or lava, is bubbling to the surface, either at a volcanic site, or at a rift where plates are separating. If newly formed rock is found along the edges of plates where they interact, older rock should be found in the middle of the plates.
