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CHAPTER 6-3 & 7 STUDY GUIDE– THE AGE OF EARTH
Chapter 6 Lesson 3
1. What changes in the Earth’s surface result from plate tectonic activity?
- Mountain building
- Volcanic Eruptions
- New shorelines
- Isolation of populations
- Closing/opening of ocean basins and seas
- Changes in ocean circulation
- Changes in climate
2. How can geographic isolation occur?
- Geographic isolation can occur when a population of individuals become separated and no longer mate with
one another
- Ex. Plate tectonics (earthquakes, mountains, volcanoes), water (rivers, lakes, streams), roads, human
encroachment on habitats such as housing and fences
3. What happens to a population when they become separated from the main group?
- The separation must be great enough that the populations are not longer in contact with each other
preventing the individuals from mating with one another
- The impact of separation is then related to the number of genetic differences (through mutations) that are
passed down from generation to generation within each population
- Without the change in genetic diversity, there can not be a new species- they remain populations
4. Describe how the movement of the plates can lead to evolution in species.
- Their movements create barriers that separate populations of species
- The separation can lead to genetic diversity through the change in genes that are passed down within the
populations
- The movement of plates may also change the climate impacting the separated populations
Chapter 7 Lesson 1
5. Draw the rock cycle. Explain how new rocks form- you should have more than one answer!!!
A. Earth’s Rocks and the Rock Cycle
1. Rocks – are made of mixtures of minerals and other materials
2. Three Major Groups of Rocks
a. Igneous Rock – forms when molten material cools or hardens below or on the Earth’s surface
b. Sedimentary Rock – forms when particles of rocks and or the remains of plants and animals are
pressed and cemented together (forms in layers below the surface)
c. Metamorphic Rock- is formed when an existing rock is changed by heat, pressure, or chemical
reactions (most form deep underground)
3. Forces inside Earth and at the surface produce a rock cycle that builds, destroys, and changes the
rocks in the crust
4. The rock cycle continues to break down, pressurize, and melt rock layers. This process produces new
rock that reaches the surface through extrusion (volcanic eruption) and intrusions (wearing away or
unconformity)
6. Why can we not date sedimentary rocks?
- We cannot date sedimentary rock since sedimentary rock is composed of the weathered particles of ALL
three types of rocks
7. Describe the law of superposition? How does this help scientist to determine the age of rocks.
- Law of Superposition- in horizontal sedimentary rock layers the oldest layer is at the bottom
- Each higher layer is younger than the layer below it
- Since scientist can not date sedimentary rock layers, they can compare the rock at the levels to determine
which is the oldest
8. List the four processes involved in the formation of sedimentary rocks. Define each.
- Weathering- mechanical or chemical erosion of rocks due to weather
- Transportation- to the movement of eroded debris, whether by rivers, glaciers, wind or ocean currents, and
tides
- Deposition- is the geological process by which material is added to a landform or land mass
- Lithification-process of changing sediment into rock
9. What are unconformities? How do they help to explain why we cannot date sedimentary rock?
- Unconformity- is a gap in the geologic record
- Different types of rocks breakdown at different rates due to weathering such as wind and water.
- This causes the Earth’s surface to be uneven therefore exposing areas that may be older that the rock layers
near it.
10. Summarize Hutton’s reasoning that allowed him to conclude that Earth’s processes are a cycle.
- Hutton saw erosion and sediment transported through wind and water. He realized that not all mountains
were the same size and shape and rivers get wider and deeper depending on the speed of the water. While
Hutton could see sediment moving, the processes were slow and results were not observable during one
lifetime.
Chapter 7 Lesson
11. Describe the process of radioactive decay.
- As a radioactive element decays, it changes into another element
- So the radioactive material in one elements goes down, the new elements radioactivity goes up
Half-life- the time it takes for half the atoms of a radioactive element to decay
12. What is half-life? How is it used to determine the absolute age of rocks?
A. Half-life- the time it takes for half the atoms of a radioactive element to decay
B. Geologist use radioactive dating to determine the absolute ages of rocks
1. Potassium-Argon Dating
a. Most useful in dating most ancient rocks
b. It has a half-life of 1.3 billion years
C. Carbon-14 Dating
1. All plants and animals contain carbon
2. Scientist measure the amount of carbon left in a sample, since carbon-14 breaks down at a
steady rate
3. Since carbon-14 has a half-life of 5,730 years, so it can only be used in dating sample less
than 50,000 years
13. What would be the advantage of using radioactive dating and relative dating to age rocks?
A. Radioactive dating can only been used in igneous rock
B. This is because sedimentary rock is made up of particles deposited by wind and water from different
ages
C. Instead they date the igneous rock intrusions and extrusions near the sedimentary rock
14. How were moon rocks used to determine the age of the Earth?
o Scientist believe that the moon is 4.5 billion years old by using tungsten-182 (radioactive dating),
or at least that is when the first meteorites appeared. Since scientist think that the moon formed
from left over materials found on Earth, then the moon must be younger than the Earth