1. Chapter 9 Worksheets
Section 1-4

2. 9.1 How and Where Volcanoes Form
Complete the graphic organizer by summarizing the main ideas of the section.

3. 9.1 How and Where Volcanoes Form
Molten rock that has formed deep inside the Earth
Subduction boundaries
Lowers melting temperature
asthenosphere
Increase in the amount of water in asthenosphere
Increase in temperature
Lowers melting temperatures of materials
Hot spots

4. 9.2 Magma and Erupted Materials
While You Read
Explain how the silica content of magma affects the explosiveness of an eruption.
The higher the silica content, the more explosive the eruption, because more viscous magmas (those with high silica content) do not allow gases to escape as easily as less-viscous magmas do.

5. 9.2 Magma and Erupted Materials
While You Read
2. Magmas form at rifts, subduction boundaries, and continental hot spots. Which type of magma would you expect to be formed at each location?
Rift; basaltic magma
Subduction boundary; andesitic
Continental hot spot; rhyolitic

6. 9.2 Magma and Erupted Materials
After You Read
Magmas are classified as rhyolitic, andesitic, and basaltic. Order the three types of magma according to the following characteristics.
Explosiveness
Greatest
Intermediate
Least
Melting temperature
Viscosity
Silica content
Gas content
Basaltic
Andesitic
Rhyolitic
Rhyolitic
Andesitic
Basaltic
Rhyolitic
Andesitic
Basaltic
Rhyolitic
Andesitic
Basaltic

7. 9.2 Magma and Erupted Materials
After You Read
List the similarities and differences between pahoehoe and aa.
Both are basaltic. Pahoehoe forms from high-temperature basaltic lava and cools into ropelike surfaces. Aa forms from cooler, slower-moving basaltic lava and cools into jagged surfaces.

8. 9.3 Volcanic Landforms
After You Read 1. In the spaces provided, draw diagrams of volcanic landforms.

9. 9.3 Volcanic Landforms Shield Volcano Cinder cone Composite volcano
Caldera

10. 9.3 Volcanic Landforms
After You Read 2. Describe how a lava plateau forms. A lava plateau forms after a long crack appears in the earth’s surface, and basaltic lava pours up through it and spreads out over the land.

11. 9.4 Extraterrestrial Vulcanism
While You Read
Add information about the characteristics, age, size, and history of extraterrestrial volcanoes that exist beyond Earth.
Earth’s moon
Mars
Venus Io
Mars has a large number of shield volcanoes, including Olympus Mons, the largest in the solar system. They are between 20 and 60 million years old.
Earth’s moon: lava flows are between 3.1 billion and 4.2 billion years old; form the lunar maria (lakes)
Venus has more than 1600 volcanoes, some of which are still active. The volcanoes are as wide as Olympus Mons, but flatter.
Io is home to active volcanoes. Lava reaches very high temperatures, about 1720°C.

12. 9.4 Extraterrestrial Vulcanism
After You Read 1. Describe the effect volcanoes on Venus have on that planet’s atmosphere. These volcanoes may account for the planet’s high temperatures. Gases from the volcanoes could be interacting with the atmosphere to continually trap heat at the planet’s surface.

13. 9.4 Extraterrestrial Vulcanism
After You Read 2. Why does the size of Olympus Mons lead scientists to infer that Mars has no moving tectonic plates. Scientists think that Olympus Mon’s huge size indicates that the planet does not have moving tectonic plates because it would have moved away from the hot spot that formed it, and in place of one giant volcano would be a chain of smaller volcanoes.