1. Unit 6 Lesson 7 Volcanoes
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2. Unit 6 Lesson 7 Volcanoes
Florida Benchmarks
SC.7.E.6.5 Explore the scientific theory of plate tectonics by describing how the movement of Earth’s crustal plates causes both slow and rapid changes in Earth’s surface, including volcanic eruptions, earthquakes, and mountain building.
SC.7.E.6.7 Recognize that heat flow and movement of material within Earth causes earthquakes and volcanic eruptions, and creates mountains and ocean basins.
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3. Magma Magic What is a volcano?
Unit 6 Lesson 7 Volcanoes
Magma Magic
What is a volcano?
A volcano is any place where gas, ash, or melted rock come out of the ground.
Many volcanoes are dormant, meaning an eruption has not occurred in a long period of time.
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4. Unit 6 Lesson 7 Volcanoes
What is a volcano?
Volcanoes form as rock below Earth’s surface melts. The melted rock, called magma, is less dense than solid rock, so it rises to the surface.
Lava, or magma that has reached Earth’s surface, and ash erupt from a vent, or opening of a volcano.
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5. What are the kinds of volcanic landforms?
Unit 6 Lesson 7 Volcanoes
What are the kinds of volcanic landforms?
The location of a volcano and the composition of magma determine the type of volcanic landforms created.
Volcanic mountains are landforms built from materials ejected from a volcano.
The shape and explosiveness of a volcano depend on the lava’s viscosity, or resistance to flow.
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6. What are the kinds of volcanic landforms?
Unit 6 Lesson 7 Volcanoes
What are the kinds of volcanic landforms?
Shield volcanoes are volcanoes with broad bases and gently sloping sides.
They are the result of mild eruptions.
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7. What are the kinds of volcanic landforms?
Unit 6 Lesson 7 Volcanoes
What are the kinds of volcanic landforms?
Cinder cones are small volcanoes with steep slopes.
They form from ash and pieces of solidified lava that fall around a small vent.
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8. What are the kinds of volcanic landforms?
Unit 6 Lesson 7 Volcanoes
What are the kinds of volcanic landforms?
Composite volcanoes are generally large, steep mountains.
They are formed of alternating layers of hardened lava flows and pyroclastic material, or ash and bits of rock that were ejected from the volcano.
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9. What are the kinds of volcanic landforms?
Unit 6 Lesson 7 Volcanoes
What are the kinds of volcanic landforms?
Fissure eruptions happen when lava flows from giant cracks, or fissures, in Earth’s surface.
Because fissures have no central opening, lava flows out the entire length of the fissure.
Fissure eruptions produce a flattened layer of cooled lava called a lava plateau.
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10. What are the kinds of volcanic landforms?
Unit 6 Lesson 7 Volcanoes
What are the kinds of volcanic landforms?
A volcanic crater is an opening or depression at the top of a volcano.
A crater is caused by eruptions.
Inside the volcano, molten rock can be found in a magma chamber.
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11. What are the kinds of volcanic landforms?
Unit 6 Lesson 7 Volcanoes
What are the kinds of volcanic landforms?
When the magma chamber empties, the roof of the chamber can collapse and leaves a large basin-shaped depression called a caldera.
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12. Eruption! Where do volcanoes form?
Unit 6 Lesson 7 Volcanoes
Eruption!
Where do volcanoes form?
Volcanoes can form at plate boundaries or within the middle of tectonic plates, which are sections of lithosphere on Earth’s surface.
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13. Where do volcanoes form?
Unit 6 Lesson 7 Volcanoes
Where do volcanoes form?
At divergent plate boundaries, where two plates are moving away from each other, fissure eruptions are likely to occur.
At hot spots, which are far from any plate boundaries, shield volcanoes, fissure eruptions, and cinder cones can occur.
At convergent plate boundaries, composite volcanoes can occur.
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14. Where do volcanoes form?
Unit 6 Lesson 7 Volcanoes
Where do volcanoes form?
At divergent boundaries, the crust stretches and gets thinner.
As it thins, the pressure on the crust and mantle rocks decreases. This causes magma to melt and flow.
Divergent plate boundaries create fissure eruptions and shield volcanoes.
Most divergent boundaries are on the ocean floor. They make a long chain of undersea volcanoes called a mid-ocean ridge.
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15. Where do volcanoes form?
Unit 6 Lesson 7 Volcanoes
Where do volcanoes form?
When a divergent boundary is located in the middle of a continent, the crust stretches until a rift valley is formed.
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16. Where do volcanoes form?
Unit 6 Lesson 7 Volcanoes
Where do volcanoes form?
At convergent boundaries, one plate usually sinks beneath the other. The mantle above the sinking plate can melt to form magma.
The magma rises to the surface and forms volcanoes.
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17. Where do volcanoes form?
Unit 6 Lesson 7 Volcanoes
Where do volcanoes form?
Magma at convergent boundaries has a high concentration of fluids, which form gas bubbles.
When gas bubbles in the magma cannot escape, pressure increases.
Eventually, magma erupts explosively, forming composite volcanoes or calderas.
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18. Where do volcanoes form?
Unit 6 Lesson 7 Volcanoes
Where do volcanoes form?
Hot spots are locations far from plate boundaries where a mantle plume, a column of extremely hot mantle rock, rises and produces volcanoes.
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19. Where do volcanoes form?
Unit 6 Lesson 7 Volcanoes
Where do volcanoes form?
Chains of volcanoes can form over time as a tectonic plate passes over the mantle plume.
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20. Unit 6 Lesson 7 Volcanoes
Living Near a Volcano
Many people around the world live near volcanoes.
The soils around a volcano are rich in minerals for growing a variety of crops, and volcanic rocks have many practical uses.
An eruption can produce destructive earthquakes, fire, ash, and lava flows.
Volcanic ash is hazardous to living things and can destroy machines and structures.
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