Inside Earth

1. Inside Earth Chapter 3: Volcanoes

2. Section 3-1 Volcanoes and Plate Tectonics

3. Sec 3-1 • Volcano—a weak spot in the crust where magma has come to the surface • Magma—the molten mixture of rock-forming substances, gases, and water from the mantle • Lava—liquid magma that reaches the surface; also the rock formed when liquid lava hardens • Ring of Fire—a major belt of volcanoes that rims the Pacific Ocean • Island arc—a string of islands formed by the volcanoes along a deep ocean trench • Hot spot—an area where magma from deep within the mantle melts through the crust above it

4. Sec 3-1: Volcanoes and Plate Tectonics What is a Volcano? Lava Volcano Magma What magma that reaches the surface is called. A weak spot in the crust where molten material, or magma, comes to the surface. A molten mixture of rock-forming substances, gases, and water from the mantle. Forms solid rock. Builds up Earth’s surface. Forms new islands and adds new rock.

5. 3-1…cont About 600 active volcanoes on land Major volcanic belt that is formed by the many volcanoes that rim the Pacific Ocean Location of Volcanoes Ring of Fire Along diverging plate boundaries (mid-ocean ridge), or in subduction zones Volcanic belts form along the boundaries of Earth’s plates. Some volcanoes form at “hot spots” away from boundaries.

6. 3-1…cont Form along the mid-ocean ridge and in a few places (Iceland and the Azores Islands in the Atlantic Ocean). Volcanoes rise above the surface. Volcanoes at Diverging Plate Boundaries

7. 3-1…cont Volcanoes at Converging Boundaries String of islands caused by volcanoes. Curve of an island arc echoes the curve of its deep-ocean trench. Happens when oceanic and continental plates collide and form deep-ocean trenches. Crust sinks, forms magma and erupts as lava to form volcanoes. Island arc

8. 3-1…cont An area where magma from deep within the mantle melts through the crust. Hot Spot Volcanoes A hot spot in the oceanic floor can gradually form a series of volcanic mountains. Hot spots can also form under continents. Yellowstone

9. Section 3-2 Volcanic Activity

10. Section 3-2: Volcanic Activity Objectives • Students will be able to describe what happens when a volcano erupts. • Students will be able to explain how the two types of volcanic eruptions differ. • Students will be able to identify some hazards of volcanoes. • Students will be able to identify types of volcanic activity other than eruptions.

11. Section 3-2: Volcanic Activity • Magma chamber—the pocket beneath a volcano where magma collects • Pipe—a long tube through which magma moves from the magma chamber to Earth’s surface • Vent—the opening through which molten rock and gas leave a volcano • Lava flow—the area covered by lava as it pours out of a volcano’s vent • Crater—a bowl-shaped area that forms around a volcano’s central opening

12. Section 3-2: Volcanic Activity • Silica—a material that is formed from the elements oxygen and silicon; silica is found in magma • Pahoehoe—a hot, fast-moving type of lava that hardens to form smooth ropelike coils • Aa—a slow-moving type of lava that hardens to form rough chunks; cooler than pahoehoe • Pyroclastic flow—the explusion of ash, cinders, bombs, and gases during an explosive volcanic eruption • Active—said of a volcano that is erupting or has shown signs of erupting in the near future

13. Section 3-2: Volcanic Activity • Dormant—said of a volcano that does not show signs of erupting in the near future • Extinct—said of a volcano that is unlikely to erupt again • Hot spring—a pool formed by groundwater that has risen to the surface after being heated by a nearby body of magma • Geyser—a fountain of water and steam that builds up pressure underground and erupts at regular intervals • Geothermal energy—energy from water or steam that has been heated by magma

14. 3-2: Volcanic Activity A Volcano Erupts Magma Rises How Magma Reaches Earth’s Surface Magma rises until it reaches the surface or a solid layer of rock. Liquid magma is less dense than the surrounding materials. The dissolved gases trapped in magma are under great pressure. As magma rises to the surface, the pressure decreases and the gases form bubbles. During a volcanic eruption, the gases dissolved in magma rush out, carrying the magma with them.

15. 3-2…continued Magma chamber-a pocket of magma that collects underneath a volcano. Pipe—a long tube in the ground that connects the magma chamber to Earth’s surface. Vent—an opening in a volcano where molten rock and gas escape Lava flow—area covered by lava as it pours out of a vent Crater—a bowl-shaped area that may form at the top of a volcano around the central vent. Inside a Volcano

16. 3-2…continued A material that’s formed from the elements of oxygen and silicon. One of the most abundant materials in Earth’s crust and mantle. More silica = thicker. Silica The forces of a volcanic eruption depends partly on the amount of gas dissolved in the magma. Thick or thin, temperature, and silica content are important factors. Characteristics of Magma Rocks formed Silica levels High—rhyolite, pumice, obsidian Obsidian—lava cools quickly Pumice—gas bubbles are trapped in lava Low--basalt High—light-colored lava that’s too sticky to flow very far. Low—flows readily and produces dark-colored lava

17. 3-2…continued The silica content of magma helps to determine whether the volcanic eruption is quiet or explosive. Explosive Eruptions Types of Volcanic Eruptions Thick magma builds up in the pipe and ends up exploding out. Breaks the lava into pieces—ash, cinders, and bombs. Quiet Eruptions Magma flows easily. The lava can flow many kilometers from the volcano’s vent. Aa: cooler and slower-moving Forms a rough surface consisting of jagged lava chunks. Pyroclastic flow Occurs when an explosive eruption hurls out ash, cinders, and bombs as well as gases. Pahoehoe: fast-moving, hot lava. Forms a solid mass of wrinkles, billows, and ropelike coils.

18. 3-2…continued Stages of a Volcano Dormant Active Extinct A volcano that is erupting or has shown signs that it may erupt in the near future. Sleeping or hibernating. Expected to wake up in the future. Dead: volcano that is unlikely to erupt again.

19. 3-2…continued Other Types of Volcanic Activity Does not involve the eruption of lava. Geothermal energy Water heated by magma that provides a clean, reliable energy source. Used as a source of electricity and to heat homes. Hot springs Geyser Forms when groundwater heated by a nearby body of magma rises to the surface and collects in a natural pool. A fountain of water and steam that erupts from the ground.

20. 3-2…continued Monitoring Volcanoes Methods Monitor The local magnetic field, water level in a volcano’s crater lake, and any gases escaping from a volcano. Temperature of underground water. Many small earthquakes caused by movement of magma into the magma chamber and pipe. Tiltmeter, laser-ranging devices, and other instruments. Magma moves underground and causes elevation and tilt to change.

21. 3-2…continued Volcano Hazards Although quiet eruptions and explosive eruptions involve different volcano hazards, both types can cause damage far from the crater’s rim. Quiet Eruption Explosive Eruption Volcanic Ash Lava flows pour from vents, setting fire to and then burying everything in their path. Can bury entire towns, damage crops, and clog car engines. Ex.—Pompeii A volcano can belch out hot, burning clouds of volcanic gases as well as cinders and bombs.

22. Section 3-3 Volcanic Landforms

23. Section 3-3 Objectives • Students will be able to identify the landforms that lava creates on Earth’s surface. • Students will be able to explain how magma hardens beneath the surface creates landforms.

24. Section 3-3: Volcanic Landforms • Shield volcano—a wide, gently-sloping mountain gradually built by lava flows and formed by quiet eruptions • Cinder cone—a steep, cone-shaped hill or mountain made of volcanic ash, cinders, and bombs piled up around a volcano’s opening • Composite volcano—a tall, cone-shaped mountain I which layers of lava alternate with layers of ash and other volcanic materials • Caldera—the large hole at the top of a volcano formed when the roof of a volcano’s magma chamber collapses

25. Section 3-3: Volcanic Landforms • Volcanic neck—a deposit of hardened magma in a volcano’s pipe • Dike—a slab of volcanic rock formed when magma forces itself across rock layers • Sill—a slab of volcanic rock formed when magma squeezes between layers of rock • Batholith—a mass of rock formed when a large body of magma cooled inside the crust

26. 3-3 Volcanic Landforms Shield Volcanos Thin layers of lava pour out of a vent and harden on top of previous layers; builds a wide, gently sloping mountain Hawaiian Islands Cinder Cone Volcanoes Paricutin, Mexico 400 m high A steep, cone-shaped hill or mountain; if lava is thick and stiff, it may produce ash, cinders, and bombs that pile up around the vent. Landforms from Lava and Ash Tall, cone-shaped mountains in which layers of lava alternate with layers of ash Mt. St. Helens, Washington Composite Volcanoes Lava Plateaus Columbia Plateau; Washington, Oregon, & Idaho Flows of lava that spread out on top of other layers; lava flows out of several long cracks and spreads out Calderas Mountain is empty and top collapses inward Crater Lake, Oregon

27. 3-3…continued Soils from Lava and Ash Originally barren Lava, ash, and cinders Hard surface breaks down to form soil Breaks down into soil Richest soils in the world Releases potassium, phosphorus, and other materials that plants need

28. 3-3…continued Dome Mountains Landforms from Magma Batholiths Formed when rising magma is blocked by horizontal layers of rock; magma forces the layers of rock to bend upward into a dome shape Mass of rock formed when a large body of magma cools inside the crust Volcanic Necks, Dikes, and Sills Volcanic Necks Dikes Sills Magma hardens in a volcano’s pipe; softer rock wears away When magma squeezes between layers of rock Sierra Nevada Mts., California Hardened magma tha forced itself across rock layers Black Hills, South Dakota

29. Section 3-4 Volcanoes in the Solar System

30. Section 3-4 Objectives • Students will be able to explain how volcanoes on Mars and Venus compare with volcanoes on Earth. • Students will be able to describe the volcanic activity found on the moons of Jupiter and Neptune.

31. 3-4: Volcanoes in the Solar System Darker Area Unusually smooth; lava flows; more than 3 billion years ago Earth’s Moon Mark where meteorites have smashed into the moon over billions of years Light-colored Crater

32. 3-4…continued Largest volcano on Venus Theia Mons Signs of widespread volcanic activity Thousands of volcanoes 800 km across and 4 km high 150 large volcanoes measuring between 100 and 600 km across and about ½ a km high Volcanoes on Venus Gently sloping shield volcanoes with broad bases Made of thin, runny lava More than 6,800 km long Long, riverlike lava flows

33. 3-4…continued Olympus Mons Volcanoes on Mars Long history of volcanic activity Over 8 times taller than Theia Mons on Venus Variety of volcanic features Volcanoes are found in only a few regions on Mars Shield volcano similar to Mauna Loa; covers an area as large as Ohio Lava flows Large shield volcanoes Cone-shaped volcanoes Biggest volcano on Mars is the largest mountain in the solar system

34. 3-4…continued Volcanic features are very different from those on Earth, Mars, and Venus Volcanoes on Distant Moons Volcanic eruptions have been observed A moon of Neptune Io A moon of Jupiter Triton Sulfur volcanoes Nitrogen Erupt like fountains or spread out like umbrellas above the colorful surface Most is frozen solid; some is melted by absorbing heat from the sun; expands and erupts through the icy crust