View
218
Download
0
Category
Tags:
Preview:
Citation preview
Table of Contents
Chapter 6 Volcanoes
Chapter Preview
6.1 Volcanoes and Plate Tectonics
6.2 Volcanic Eruptions
6.3 Volcanic Landforms
6.4 California Geology
Chapter Preview Questions
1. Igneous rocks form when
a. sediment is compacted and cemented.
b. rocks are changed by heat and pressure.
c. sediment is heated and cooled.
d. lava and magma cool and harden.
Chapter 6 Volcanoes
Chapter Preview Questions
1. Igneous rocks form when
a. sediment is compacted and cemented.
b. rocks are changed by heat and pressure.
c. sediment is heated and cooled.
d. lava and magma cool and harden.
Chapter 6 Volcanoes
Chapter Preview Questions
2. Melted material that erupts from a volcano is called
a. magma.
b. sediment.
c. lava.
d. mica.
Chapter 6 Volcanoes
Chapter Preview Questions
2. Melted material that erupts from a volcano is called
a. magma.
b. sediment.
c. lava.
d. mica.
Chapter 6 Volcanoes
Chapter Preview Questions
3. Why do volcanoes erupt?
a. They are hot and fiery.
b. They form beneath the ocean floor.
c. Gases in magma expand as it rises to the surface.
d. Lava is a pure liquid.
Chapter 6 Volcanoes
Chapter Preview Questions
3. Why do volcanoes erupt?
a. They are hot and fiery.
b. They form beneath the ocean floor.
c. Gases in magma expand as it rises to the surface.
d. Lava is a pure liquid.
Chapter 6 Volcanoes
Chapter Preview Questions
4. Which of these does NOT rapidly change Earth’s
land surface?
a. earthquakes
b. mountain building
c. landslides
d. volcanic eruptions
Chapter 6 Volcanoes
Chapter Preview Questions
4. Which of these does NOT rapidly change Earth’s
land surface?
a. earthquakes
b. mountain building
c. landslides
d. volcanic eruptions
Chapter 6 Volcanoes
You know that if you want to open a bottle of soda, you must do so carefully. Otherwise, the soda might spray out of the bottle as soon as you loosen the cap. What causes the soda to rush out with such force? How is this similar to what happens when a volcano erupts? Explain.
What causes volcanoes, and how do they change
Earth’s surface?
Chapter 6 Volcanoes
Use Clues to Determine Meaning
Chapter 6 Volcanoes
Some volcanoes result from hot spots in Earthís mantle. A hot spot is an area where material from within the mantle rises and then melts. A volcano forms above a hot spot when the hot material erupts through the crust and reaches the surface.A hot spot in the ocean oor can gradually form a series of volcanic mountains. For example, the Hawaiian Islands formed one by one over millions of years as the Pacific plate drifted over a hot spot.
Example
Unfamiliar wordsHot spot isthe subject ofthe sentence.
Definition,follows boldface
Explanation
Apply It!
Review the clues to the meaning of hot spot. Then complete the following.
1. What clue tells you that hot spot might be followed by a definition?
The term is in boldface and is the subject of the sentence.
2. What example helps you understand hot spots?
The Hawaiian Islands formed one by one over millions of years as thePacific plate drifted over a hot spot
Chapter 6 Volcanoes
End of Chapter Preview
Chapter 6 Volcanoes
Describe what happens along a fault beneath Earth’s surface when an earthquake occurs?
How do volcanoes change the land?
Volcanoes
Section 1:Volcanoes and Plate
TectonicsWhere are most of Earth’s volcanoes found?
How do hot spot volcanoes form?
Chapter 6 Volcanoes
A volcanovolcano is a weak spot in the crust where molten material, or magma, comes to the surface.
MagmaMagma is molten material that has not reached the surface and is still underground.
LavaLava is molten material, or magma, that has reached the surface.
Ring of FireRing of Fire is a major volcanic belt that rims or circles the Pacific Ocean.
Island ArcIsland Arc is a string of islands formed by weak spots or hot spotshot spots in the crust where magma burns through.
Volcanoes and Plate Boundaries
Volcanic belts form along the boundaries of Earth’s plates.
Chapter 6 Volcanoes
Volcanoes and Plate BoundariesVolcanoes often form where two oceanic plates collide or where an oceanic plate collides with a continental plate. In both situations, an oceanic plate sinks through a trench. Rock above the plate melts to form magma, which then erupts to the surface as lava.
Chapter 6 Volcanoes
Hot Spot Volcanoes
A volcano forms above a hot spot when magma erupts through the crust and reaches the surface.
Chapter 6 Volcanoes
More on Volcanoes
Click the PHSchool.com button for an activityabout volcanoes.
Chapter 6 Volcanoes
End of Section:Volcanoes and Plate Tectonics
Chapter 6 Volcanoes
What causes volcanoes to form at a spreading boundary?
Where are most of Earth’s volcanoes found? Explain.
Describe the order of parts through which magma travels
as it moves to the surface.
Which is more likely to be dangerous – a volcano that
erupts frequently or a volcano that has been inactive for a
hundred years? Why?
Section 2:Volcanic Eruptions
What happens when a volcano erupts?
What are the two types of volcanic eruptions?
What are a volcano’s stages of activity?
Chapter 6 Volcanoes
Volcanic Eruptions
Magma Reaches Earth’s Surface
When a volcano erupts, the force of the expanding gases pushes magma from the magma chambermagma chamber through the pipepipe until it flows or explodes out of the ventvent.
Chapter 6 Volcanoes
Magma Reaches Earth’s Surface
Chapter 6 Volcanoes
Magma chamberMagma chamber is a pocket beneath a volcano where magma is collected or stored.
Magma Reaches Earth’s Surface
Chapter 6 Volcanoes
PipePipe is a long tube inside a volcano that connects the magma chamber to the Earth’s surface.
Magma Reaches Earth’s Surface
Chapter 6 Volcanoes
VentVent is an opening through which molten rock and gas leave the volcano.
Magma Reaches Earth’s Surface
Chapter 6 Volcanoes
Lava flowLava flow is the area covered by lava as it pours out of a vent.
Magma Reaches Earth’s Surface
Chapter 6 Volcanoes
CraterCrater is a bowl-shaped area that may form at the top of a volcano.
Magma Reaches Earth’s Surface
Chapter 6 Volcanoes
PahoehoePahoehoe is a very thin, fast moving lava. Pahoehoe contains low amounts of silica, which gives it it’s thinness. When Pahoehoe hardens, it forms wrinkle and rope-like rock formations. Pahoehoe is hotter than Aa.
Magma Reaches Earth’s Surface
Chapter 6 Volcanoes
AaAa is a very thick, slow moving lava. Aa contains high amounts of silica, which gives it it’s thickness. When aa hardens, it forms a rough surface consisting of jagged (sharp) lava chunks.
Magma Reaches Earth’s Surface
Chapter 6 Volcanoes
Pyroclastic flowPyroclastic flow is an explosive eruption that includes hot gases, cinders (volcanic ash), and bombs (volcanic rocks).
Composite Volcano Eruption Activity
Click the Active Art button to open a browser window and access Active Art about composite volcano eruption.
Chapter 6 Volcanoes
Magma Composition
Magma varies in composition and is classified according to the amount of silica it contains. The graphs show the average composition of the two types of magma. Use the graphs to answer the questions.
Chapter 6 Volcanoes
Magma Composition
Silica, other oxides, and other solids.
Reading Graphs:
Study both graphs. What materials make up both types of magma?
Chapter 6 Volcanoes
Magma Composition
Rhyolite-forming magma; about 70 percent.
Reading Graphs:
Which type of magma has more silica? About how much silica does this type of magma contain?
Chapter 6 Volcanoes
Magma Composition
About 60 percent
Estimating:
A third type of magma has a silica content that is halfway between that of the other two types. About how much silica does this type of magma contain?
Chapter 6 Volcanoes
Magma Composition
Rhyolite-forming magma would have higher viscosity because it is higher in silica.
Predicting:
What type of magma would have a higher viscosity? Explain.
Chapter 6 Volcanoes
Kinds of Volcanic Eruptions
Within the last 150 years, major volcanic eruptions have greatly affected the land and people around them.
Chapter 6 Volcanoes
Deadly Eruptions
Stages of Volcanic Activity
Chapter 6 Volcanoes
ActiveActive volcanoes are considered “live” meaning that it is erupting, or has shown signs that it may erupt in the near future
Lassen PeakLassen PeakMount ShastaMount Shasta
Stages of Volcanic Activity
Chapter 6 Volcanoes
DormantDormant volcanoes are considered “asleep” or “sleeping bears” meaning that they may become active in the future
Long Valley Long Valley CratersCraters
Stages of Volcanic Activity
Chapter 6 Volcanoes
ExtinctExtinct volcanoes are considered “dead” meaning that it is unlikely that they will erupt again
AucklandAuckland
St. LuciaSt. Lucia
End of Section:Volcanic Eruptions
Chapter 6 Volcanoes
Section 3: Volcanic Landforms
What landforms do lava and ash create?
How does magma that hardens beneath the surface create landforms?
Chapter 6 Volcanoes
Types of Volcanoes
Landforms From Lava and Ash
Volcanic eruptions create landforms made of lava, ash, and other materials. These landforms include composite composite volcanoesvolcanoes, shield volcanoesshield volcanoes, cinder cone volcanoescinder cone volcanoes, and lava plateauslava plateaus.
Chapter 6 Volcanoes
Landforms From Lava and Ash
Composite VolcanoesComposite Volcanoes have quiet eruptions that alternate with explosive eruptions, forming layers of lava and ash.
Chapter 6 Volcanoes
Mayon, PhilippinesCotopaxi, Ecuador
Landforms From Lava and Ash
Shield VolcanoesShield Volcanoes have quiet eruptions and have gentle slopes, which are not steep.
Chapter 6 Volcanoes
Mauna Loa, Hawaii Erta Ale, Ethiopia
Landforms From Lava and Ash
Cinder Cone VolcanoesCinder Cone Volcanoes have explosive eruptions of ash, cinders, and bombs that form a cone-shaped hill.
Chapter 6 Volcanoes
Mount Etna, ItalySP Crater, Arizona
Landforms From Lava and Ash
Lava PlateausLava Plateaus are formed from runny lava (pahoehoe) that cools in flat sheets of rock. Over time these layers form high plateaus.
Chapter 6 Volcanoes
Steamboat Rock, Washington Hawaii
Landforms From Lava and Ash
CalderasCalderas are formed when a magma chamber is emptied after an eruption and the volcano mountain collapses into the empty space creating a crater.
Chapter 6 Volcanoes
Aniakchak, Alaska Crater Lake, Oregon
Landforms From Lava and Ash
A calderacaldera forms when an volcano’s magma chamber empties and the roof of the chamber collapses. The result is a large, bowl-shaped calderacaldera.
Chapter 6 Volcanoes
Landforms From Magma
Features formed by magma include volcanic necksvolcanic necks, dikesdikes, and sillssills, as well as batholithsbatholiths and dome mountainsdome mountains.
Chapter 6 Volcanoes
Landforms From Magma
BatholithsBatholiths
Chapter 6 Volcanoes
Landforms From Magma
Volcanic NecksVolcanic Necks
Chapter 6 Volcanoes
Landforms From Magma
DikesDikes
Chapter 6 Volcanoes
Landforms From Magma
SillsSills
Chapter 6 Volcanoes
Batholiths
A batholithbatholith is a mass of rock formed when a large body of magma cools inside the crust. Several large batholithsbatholiths form the core of mountain ranges in western North America. Half Dome in Yosemite National Park, California, is part of the Sierra Nevada batholithbatholith.
Chapter 6 Volcanoes
Links on Volcanic Effects
Click the SciLinks button for links on volcanic effects.
Chapter 6 Volcanoes
End of Section:Volcanic Landforms
Chapter 6 Volcanoes
Section 4:California Geology
How does plate tectonics help to explain features of California’s geology?
Chapter 6 Volcanoes
Plate Tectonics and California
The movements of three plates have shaped the geologic features of California over millions of years.
Chapter 6 Volcanoes
Plate Tectonics and California
Many geologic processes worked together to form California’s landscape
of volcanoes, faults, mountain ranges, and basins.
Chapter 6 Volcanoes
End of Section: California Geology
Chapter 6 Volcanoes
Chapter 6 Volcanoes
QuickTake Quiz
Click to start quiz.
Chapter 6 Volcanoes
Recommended