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Table of Contents. Volcanoes and Plate Tectonics Properties of Magma Volcanic Eruptions Volcanic Landforms. - Volcanoes and Plate Tectonics. Volcanoes and Plate Boundaries. Volcanic belts form along the boundaries of Earth’s plates. Discussion Questions. What is a volcano? - PowerPoint PPT PresentationTRANSCRIPT
Volcanoes
Volcanoes and Plate Tectonics
Properties of Magma
Volcanic Eruptions
Volcanic Landforms
Table of Contents
Volcanoes - Volcanoes and Plate Tectonics
Volcanoes and Plate BoundariesVolcanic belts form along the boundaries of Earth’s plates.
Volcanoes
Discussion Questions
• What is a volcano?• A volcano is an opening, or rupture, in a planet's surface
or crust, which allows hot magma, volcanic ash and gases to escape from below the surface.
• What is the difference between magma and lava?• Magma (from Greek μάγμα "paste") is a mixture of
molten rock, volatiles and solids that is found beneath the surface of the Earth, and is expected to exist on other terrestrial planets.
• Lava refers both to molten rock expelled by a volcano during an eruption and the resulting rock after solidification and cooling.
Volcanoes
Volcanoes and Plate Boundaries• Volcanoes 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.
- Volcanoes and Plate Tectonics
Volcanoes
Hot Spot Volcanoes
A volcano forms above a hot spot when magma erupts through the crust and reaches the surface.
- Volcanoes and Plate Tectonics
Volcanoes
Ring of Fire• http://www.youtube.com/watch?v=gRlj5vjp3Ko
Volcanoes
Questions Answers
Asking QuestionsBefore you read, preview the red headings. In a graphic organizer like the one below, ask a where, what, or how question for each heading. As you read, write the answers to your questions.
Where are volcanoes found?
Most volcanoes are found along plate boundaries.
What are hot spots? A hot spot is an area where material from deep within the mantle rises and then melts, forming magma.
- Volcanoes and Plate Tectonics
Volcanoes
End of Section:Volcanoes and Plate Tectonics
Volcanoes
Overview
• Viscosity refers to the resistance of a liquid to flowing• Different liquids have different viscosities allowing some to
flow more easily compared to others• This is due to the particles that make up the liquid and the
friction that exists when they are in motion• Different types of magma have different viscosities which are
a result of temperature and silica content
• Silica (SiO2) is a compound consisting of Silicon and
Oxygen particles bonded together• Silica content of magma varies between 50-70% on average• Temperature of magma and lava varies between 750 – 1200
C
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.
- Properties of Magma
Volcanoes
Magma Composition
Silica, other oxides, and other solids.
Reading Graphs:
Study both graphs. What materials make up both types of magma?
- Properties of Magma
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?
- Properties of Magma
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?
- Properties of Magma
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.
- Properties of Magma
Volcanoes
TYPES OF LAVA There are three categories of lava, classified on the basis of its silica (SiO2) content, which affects how readily it flows. 1. BASALTIC LAVA a. Relatively low SiO2 content (less than 52%) b. Relatively low viscosity (flows readily when hot)
2. ANDESITIC LAVA a. Intermediate SiO2 content (between 52 and 63%) b. Intermediate viscosity (does not flow readily) 3. RHYOLITIC LAVA a. Relatively high SiO2 content (above 68%) b. Relatively high viscosity (flows like wet concrete)
Volcanoes
Volcanoes
Pahoehoe lava is characterized by a smooth, billowy, or ropy surface. Pahoehoe is hot, moves fast, and has lower viscosity.
Volcanoes
Aa is characterized by a rough or jagged surface. Aa lava flows tend to be relatively thick compared to pahoehoe flows meaning they have lower temperature and higher viscosity.
Volcanoes
Main Idea
Detail Detail Detail
Identifying Main IdeasAs you read the section “Types of Viscosity of Magma,” write the main idea in a graphic organizer like the one below. Then write three supporting details that further explain the main idea.
Magma’s viscosity depends on its physical and chemical properties.
Magma is made of elements and of
compounds, among them silica.
Viscosity is a property of magma.
Viscosity depends on silica content and
temperature.
- Properties of Magma
Volcanoes
End of Section:Properties of
Magma
Volcanoes
Anatomy of a VolcanoWhen a volcano erupts, the force of the expanding gases pushes magma from the magma chamber through the pipe until it flows or explodes out of the vent.
- Volcanic Eruptions
Volcanoes
Key Terms• Magma chamber is the area beneath the volcano where magma
collects
• The pipe is the vertical tube connecting the magma chamber to the vent (or outside world)
• The vent is the opening near the top of the volcano where gas and magma flow out towards the surface
• Side vents refer to pipe like projections that run on the sides of the volcanoes mountainous structure
• A crater is the bowl-shaped area that can form around the top of the volcano or vent
Volcanoes
Volcanic EruptionsBasically there are two types of volcanic eruptions: Quiet & Explosive
Quiet eruptions are what you have on the island of Hawaii
*Quiet eruptions occur when the magma has:
1. Lower silica content
2. Higher temperature
3. Lower viscosity
Explosive eruptions are what you typically have along subduction zones
*Explosive eruptions occur when the magma has:
4. Higher silica content
5. Lower temperature
6. Higher viscosity
Volcanoes Volcanic Hazards
• Ash• Gas• Lahars• Tephra• Landslides• Lava Flows• Pyroclastic Flows
Volcanoes
Volcanic Activity Classification
• Volcanologists use the terms active, dormant, or extinct to describe a volcano’s stage of activity
• An active volcano refers to a current eruption taking place or a possibility of it erupting in the near future
• A dormant volcano refers to a volcano that has not erupted for an extended period of time, but still can erupt at any given time
• An extinct volcano also has not erupted for a very long time and poses little to no threat of erupting again
*The prediction of a volcano eruption is more accurate than earthquake prediction, but still not perfected!
Volcanoes
Kinds of Volcanic Eruptions
Within the last 150 years, major volcanic eruptions have greatly affected the land and people around them.
- Volcanic Eruptions
Volcanoes
What You Know
What You Learned
Using Prior KnowledgeBefore you read, look at the section headings and visuals to see what this section is about. Then write what you know about volcanic eruptions in a graphic organizer like the one below. As you read, write what you learn.
1. Lava flows out of a volcano.2. Eruptions are not all the same.3. Some volcanoes are dormant.
1. Magma rises toward Earth’s surface through a pipe that leads to a vent.
2. Differences in gas and silica content cause some eruptions to be explosive and others to be quiet.
3. Dormant volcanoes can become active at any time.
- Volcanic Eruptions
Volcanoes
End of Section:Volcanic
Eruptions
Volcanoes
Landforms From Lava and Ash
Volcanic eruptions create landforms made of lava, ash, and other materials. These landforms include composite volcanoes, shield volcanoes, cinder cone volcanoes, and lava plateaus.
- Volcanic Landforms
Volcanoes
Landforms From Lava and Ash
A caldera forms when an volcano’s magma chamber empties and the roof of the chamber collapses. The result is a large, bowl-shaped caldera.
- Volcanic Landforms
Volcanoes
Landforms From Magma
Features formed by magma include volcanic necks, dikes, and sills, as well as batholiths and dome mountains.
- Volcanic Landforms
Volcanoes
Batholiths
A batholith is a mass of rock formed when a large body of magma cools inside the crust. Several large batholiths form the core of mountain ranges in western North America. Half Dome in Yosemite National Park, California, is part of the Sierra Nevada batholith.
- Volcanic Landforms
Volcanoes
OutliningAs you read, make an outline about volcanic landforms that you can use for review. Use the red headings for the main topics and the blue headings for the subtopics.
Volcanic Landforms
I. Landforms From Lava and AshA. Shield VolcanoesB. Cinder Cone VolcanoesC. Composite VolcanoesD. Lava PlateausE. CalderasF. Soils From Lava and Ash
II. Landforms From MagmaA. Volcanic Necks, Dikes and
SillsB. Dikes and SillsC. BatholithsD. Dome Mountains
III. Geothermal ActivityA. Hot SpringsB. GeysersC. Geothermic Energy
- Volcanic Landforms
Volcanoes
End of Section:Volcanic
Landforms
Volcanoes
Volcanicmountains
Compositevolcanoes
include
produce produce produce
Lava
Graphic Organizer
Shield volcanoes
Cinder cones
Lava and ash
Ash, cinders, and bombs
Volcanoes
End of Section:Graphic Organizer