Volcanoes
Earth Science - Middle School
Volcanoes
Multimedia Lesson
Plate Tectonics
Multimedia Lesson
Earth's Interior
Presentation
Heat Transfer and Convection Currents
Presentation
Sea-Floor Spreading
Presentation
Introduction to Volcanoes
Presentation
Volcanoes and Plate Boundaries
Presentation
Properties of Magma
Presentation
Volcanic Eruptions
Presentation
Volcano Classification
Presentation
Life Cycle of a Volcano
Presentation
Volcanic Landforms, Hot Springs and Geysers
Presentation
Volcano Simulator
Virtual Lab
Types of Volcanoes
Interactive
Volcanoes
Study Guide
Volcanoes
Quiz
Volcanoes
Quiz
Volcanoes
Flash Cards
Volcanoes
Flash Cards
Volcanoes
Worksheet
Volcanoes
Worksheet
Volcanoes
Game
Volcanoes
Game
Volcanoes
Vocabulary List
Volcanoes
Vocabulary List
What is a Volcano?
Flip Chart
Volcanoes and Plate Boundaries
Flip Chart
The Ring of Fire
Flip Chart
Properties of Magma
Flip Chart
Inside a Volcano
Flip Chart
Volcanic Eruptions
Flip Chart
Volcanic Classification
Flip Chart
Life Cycle of Volcanoes
Flip Chart
Volcanic Landforms, Hot Springs and Geysers
Flip Chart
All About Volcanoes Vocabulary Review
Flip Chart
Volcanoes and Plate Boundaries
Flip Chart
Study Guide Volcanoes
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VOLCANOES The intense heat and pressures in the mantle turn solid rock into liquid magma. Magma comes out through the surface of the crust to form volcanoes. The type of volcano formed and the style of eruption depends on the silica content, and therefore, the viscosity of the magma. The “Ring of Fire” is a series of volcanoes that indicates tectonic plate boundaries and contains about 75% of the world’s active volcanoes. The “Ring of Fire” marks the boundary of the Pacific Ocean basin. Volcanoes and Plate Boundaries There are two distinct types of volcanic eruptions. Explosive eruptions occur when highly viscous magma (that is, magma with a very high silica content) erupts through continental crust. Explosive eruptions are truly explosive and extremely destructive. They throw hot ash, particles and chunks of rock, and gases into the air. Ash from explosive eruptions can travel into the stratosphere and encircle the entire Earth for many years. This ash layer can lower global temperatures. Explosive eruptions are typical of tectonic plate boundaries where an oceanic plate is subducted under a continental plate. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
The ash and rock that is extruded by explosive volcanoes is called pyroclastic material. A mudflow of mixed water and volcanic ash can travel very, very quickly down a volcano and cause widespread destruction. This volcanic mudflow is called a lahar. The second type of volcanic eruption is called non-explosive. Liquid, less viscous lava pours out of the crust and flows onto the surface in non-explosive eruptions. (When liquid rock is in the crust it is called magma. When it flows or explodes onto the surface it is then called lava.) Non-explosive eruptions occur at mid-ocean ridges and other places where tectonic plates pull away from each other. They can also occur in the middle of oceanic plates at hot spots. A hot spot is an extremely thin portion of the oceanic plate that has a magma body very close to the surface. The Hawaiian Islands are non-explosive volcanoes that formed at a hot spot in the Pacific Ocean basin. Sometimes lava flows out of a long crack in the crust rather than through a hole. When this happens, extremely thick layers of lava can cover thousands of square miles. These thick, extensive layers of lava are called lava plateaus. Lesson Checkpoint: How did the Hawaiian Islands form? © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
Volcanic Eruptions and Properties of Magma The type of a volcanic eruption is determined by the physical properties of the magma extruded by a particular volcano. In short, non-explosive volcanoes extrude lava that has lower viscosity (in other words, it is runnier). By comparison explosive volcanoes extrude pieces of hot rock because the lava has a high viscosity (in other words, it is very, very sticky). The igneous rock type that flows from non-explosive volcanoes is basalt. Different names are given to the types of lava that pours from a non-explosive volcano. Pahoehoe lava is ropy-looking because the outer crust hardens but underneath the liquid lava continues to flow. Here is a picture of pahoehoe lava. Aa lava is blocky lava that cooled into irregular, sharp-edged chunks. Lava that cools instantly into volcanic glass is called obsidian. Small and large tear-shaped blobs of lava can be thrown from the volcano. These are called volcanic bombs. Obsidian When lava pours out of mid-ocean ridges onto the ocean floor, it cools rapidly from contact with the very cold water of the deep ocean. The result is the accumulation of rounded masses of basalt. This is called pillow basalt. Pillow basalts found on dry land indicate that that land was, at one time in geologic history, under an ocean and volcanically active. Lesson Checkpoint: What is obsidian? © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
Three Types of Volcanoes Volcanoes can also be classified based on their shape. The three categories are cinder cones, shield volcanoes and stratovolcanoes. Cinder cones are relatively small volcanoes formed by the accumulation of pyroclastic material. The sides of cinder cones are steep. Shield volcanoes are wide, flat volcanoes formed by the non- explosive flow of lava onto the surface. The largest shield volcano in our solar system is Olympus Mons on Mars. Stratovolcanoes are the most common type of volcanoes. They are formed by the alternating of layers of pyroclastic material and lava flows. Below are pictures of each type of volcano. Cinder cone Mauna Loa, a shield volcano, in Hawaii © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
Mt. St. Helens, a stratovolcano, erupted in 1980 in Washington State Lava makes its way from deep in the crust to the surface through a tube called the vent. At the top of many volcanic vents is a cone- shaped depression formed when pyroclastic material erupts from the volcano. Geologists call this depression a crater. After a volcano has erupted, the magma chamber that fed magma to the volcano can become partially emptied. In time the volcano can collapse into this chamber, forming a large depression on the surface. This depression is called a caldera. Lesson Checkpoint: Name the three categories of volcanoes. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
What Causes Hot Springs and Geysers? In special situations, magma reservoirs occur very near the surface. The intense heat from the magma heats the groundwater. Hot groundwater can come to the surface in a number of interesting and spectacular ways. Geysers are fountains of hot water that spray out of the ground at regular intervals. The water is heated and when it reaches a certain pressure it shoots out of the ground until the pressure is relieved. Then new water percolates through the rock, is heated and will eventually spray out of the ground. Old Faithful is a famous geyser in Yellowstone National Park. When the water is not under pressure, it flows out of the ground. This is called a hot spring. Mud pots form when heated water mixes with sediments and collects in pools. These pools typically bubble like thick stew in a pot. In some situations this naturally heated water can be collected and used as an alternative form of energy. This is called geothermal energy (literally, “earth heat energy”). The hot water is collected and piped directly into buildings as a source of heat. It can sometimes be used to drive turbines to generate electricity. © Copyright NewPath Learning. All Rights Reserved. Permission is granted for the purchaser to print copies for non-commercial educational purposes only. Visit us at www.NewPathLearning.com.
Table Of Contents: Volcanoes
1. Introduction to Volcanoes
2.1. Magma Formation
Magma is a mixture of liquid rock, gases and water formed from intense heat and pressure in the Earth's mantle.
2.2. What Is a Volcano?
A volcano forms when magma moves through the crust and erupts onto the surface of the Earth. Magma that flows onto the Earth's surface is called lava. Layers of cooled lava harden into rock and build up on the earth's surface around a volcano.
2. Volcanoes and Plate Boundaries
3.1. Volcanoes at Plate Boundaries
Most of the Earth's volcanoes are located at tectonic plate boundaries. These volcanoes are found on both continental and oceanic crust.
3.2. Ring of Fire
The belt of volcanoes along the boundary of the Pacific Ocean is called the Ring of Fire because it contains about 75% of the world's active volcanoes.
3.3. Volcanoes at Divergent Boundaries
Mid-ocean ridges form from lava pouring onto the ocean floor at divergent plate boundaries. On land, divergent boundaries produce chains of active volcanoes.
3.4. Volcanoes at Convergent Boundaries
At convergent boundaries, oceanic plates are subducted and magma forms from melting crust. Eruptions create volcanic island arcs in the ocean and volcanic mountain ranges on land.
3.5. Hot Spot Volcanoes
Some volcanoes form over hot spots that are not located along plate boundaries. A hot spot occurs when rising magma is close to the Earth's surface. The islands of Hawaii were formed over a hot spot in the Pacific Ocean.
3. Properties of Magma
4.1. Magma Properties Can Vary
Not all magma is the same. The composition and viscosity of magma can vary. These properties affect how fast the lava flows and the type of volcano that forms.
4.2. Magma Composition
Although magma is a complex mixture, it is primarily composed of silica. Magma can contain from 50 to 70 % silica.
4.3. Magma Viscosity
Viscosity is a liquid's resistance to flow. High viscosity magma is sticky and flows very slowly. Low viscosity magma flows more quickly.
4.4. Different Types of Lava
Magma with high silica content has a higher viscosity and produces light-colored lava that later forms rhyolite. Magma with less silica and a lower viscosity produces dark lava that forms basalt.
4.5. Temperature Affects Magma and Lava
Higher temperatures make magma and lava more fluid, lowering the viscosity. Pahoehoe is a type of very hot, fast-moving lava with low viscosity. Slower-moving, cooler, high-viscosity lava is known as aa.
4. Pause and Interact
5.1. Review
Use the whiteboard tools to complete the activity.
5. Volcanic Eruptions
6.1. Inside a Volcano
Beneath the surface of a volcano is a magma reservoir where rock that is exposed to heat and pressure changes into magma. A long tube through the crust called a pipe connects the reservoir to the surface.
6.2. Vents and Craters
Lava flows out onto the surface through an opening called a vent. Some volcanoes form smaller side vents where lava and gases escape. A cone-shaped depression called a crater often forms during explosive eruptions.
6.3. Why Does a Volcano Erupt?
When magma rises toward the surface, gas bubbles expand and increase in pressure. The force of the gas pushes the magma out of the vent and causes an eruption.
6.4. Quiet Eruptions
There are two types of eruptions—quiet and explosive. Quiet eruptions are non-explosive and occur in volcanoes with low-viscosity, low-silica magma. The fast-moving lava flows out of the vent and across the surface of the land.
6.5. Explosive Eruptions
Explosive eruptions occur in volcanoes with thick, high-viscosity magma that is high in silica. Magma builds up within the volcano's pipe rather than flowing out. Pressure increases until an explosive eruption occurs.
6.6. Pyroclastic Flow and Lahar
Explosive eruptions release a mixture called a pyroclastic flow made up of hot ash, rocks and gases. A fast-moving mudflow called a lahar can also form during an explosive eruption.
6.7. Volcanic Material and Rocks
Volcanic material can be found in all different sizes from tiny ash particles, to cinders, to large pieces called volcanic bombs. Obsidian, pumice, basalt, and rhyolite are all igneous rocks that form from volcanic eruptions.
6. Volcano Classification
7.1. Volcano Classification
Volcanoes are classified by their shape. There are three types of volcanoes—composite, shield and cinder cone.
7.2. Composite Volcano
A composite volcano forms from alternating layers of ash and layers of flowing lava. Composite volcanoes have steep sides and may have a crater on top.
7.3. Cinder Cone Volcano
A cinder cone is a small, steep volcano that is created from the accumulation of ash and pyroclastic material. They often have a crater where the top of the volcano was blown off during an explosive eruption.
7.4. Shield Volcano
Shield volcanoes are wide, flat volcanoes formed by non-explosive lava flows. Layers of hardened lava result in a gently sloping mountain. The Hawaiian Islands were formed from shield volcanoes.
7. Life Cycle of a Volcano
8.1. Stages of Activity
Volcanoes have different stages of activity. An active volcano is one that is erupting or showing signs of erupting soon. A dormant volcano has not erupted for a while, but is expected to erupt in the future. An extinct volcano will probably never erupt again.
8.2. Monitoring Volcanoes
Geologists use a variety of technical instruments to study volcanoes and predict eruptions. Earthquakes, increases in ground temperature and escaped gases provide warning signals of potential eruption.
8.3. Destruction Caused by Volcanoes
Volcanoes can cause widespread damage. Huge clouds of ash may bury towns, and volcanic gases can be deadly. A lava flow covers everything in its path and can start fires and landslides.
8. Pause and Interact
9.1. Review
Use the whiteboard tools to complete the activity.
9.2. Structure of a Volcano
Click on the Terms button. Then click and drag each term to the correct box. Use the reset button to clear the terms and start over. Use the gear button to customize the draggable terms.
9.3. Types of Volcanoes
Follow the onscreen instructions.
9. Volcanic Landforms, Hot Springs and Geysers
10.1. Caldera
After an eruption, the magma reservoir of a volcano may be partially emptied. Some volcanoes collapse into this chamber, forming a large depression on the surface called a caldera.
10.2. Volcanic Necks and Dome Mountains
Volcanic necks are the remnants of a volcanic plug within a previously active volcano. The hardened magma is exposed by weathering and erosion. A dome mountain is magma that hardens below the crust and is uplifted.
10.3. Hot Springs and Geysers
Magma that exists very close to the Earth's surface can warm the groundwater. Hot springs and geysers are formed when this water emerges on the surface of the Earth.
10. Vocabulary Review
11.1. Vocabulary Matching Review
After an eruption, the magma reservoir of a volcano may be partially emptied. Some volcanoes collapse into this chamber, forming a large depression on the surface called a caldera.
11. Virtual Investigation
12.1. Volcano Simulator
The amount of silica and the amount of dissolved gases are two important properties of magma. In this virtual investigation you will study simulated volcanoes by selecting the composition of the magma and then making predictions about a volcano with this type of magma. After watching a simulated volcano erupt, you can determine if your predictions were correct.
12. Assesment
13.1. Volcanoes
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