Chapter 10: Mountains and Volcanoes

1. Chapter 10: Mountains and Volcanoes 10.1: Movement of rock builds mountains 10.2: Volcanoes form as molten rock erupts 10.3: Volcanoes affect Earth’s land, air, and water

2. Review t/f • The main gases in volcanic eruptions are water vapor and oxygen • Water vapor and carbon dioxide • Much of Earth’s volcanic activity takes place underwater along spreading centers in the oceans • True • Lava forms as tectonic plates sink into subduction zones? • Magma forms in this process • Pyroclastic flows are dense and dangerous clouds of superhot gases and rock fragments that race downhill during eruptions • true

3. Which is more dangerous to live near, Mauna Loa or Mount Shasta? • Mauna Loa: shield volcano, one of the most active volcanoes on Earth, frequently produces large amounts of lava that flow long distances • Mount Shasta: composite volcano, has erupted at least once every 600 to 800 years for the past 10,000 years, erupts with devastating violence • Mt. Shasta erupts less often than Mauna Loa, but its explosions are much more violent due to built-up pressure • Volcanic gases from Mauna Loa are a constant danger to people with breathing difficulties

4. Volcanoes affect Earth’s land, air, and water • Can knock down forests and clog rivers • Build as well as destroy – form new land • Lava flows can form new, rich soil • Goma, in the eastern Democratic Republic of the Congo • Lava flow cut the city in half, destroying the homes of tens of thousands of people

5. Immediate Effects • Effects of a volcanic eruption depend on the material ejected • Lava flows can form new rock • Ash falls, landslides, mudflows, pyroclastic flows, and steam explosions: • Lava Flows: people can escape, but it still destroys! • Volcanic Ash: weight of fallen volcanic ash can collapse buildings • Contains rocks • Makes roads slippery • Clogs machinery (cars and airplanes) • Suffocate plants, animals, people

7. Immediate Effects • Mudflows • Landslides of loose rocks and soil mixed with water • Heat from an eruption melts ice and snow • Ash can also mix with rivers flowing from volcanoes • Pyroclastic flows • a dense cloud of superhot gases and rock fragments that races downhill • Can knock down or burn everything in its way • Tend to follow valleys but fast-moving flows can sweep up and over hills

9. Immediate Effects • Landslides • Rapid downhill movement of rock and soil • May be caused by magma moving underground, an eruption, an earthquake, or even heavy rainfall • Can cause a tsunami! • Steam Explosions • When magma comes near water or in contact with it

10. Long-term effects • Mount Pinatubo in 1991 – threw out a lot of volcanic ash and rock fragments • the area gets heavy rains each year • Mudflow formed as large amounts of rainwater mix with ash and other loose material from the eruption • Has destroyed the homes of more than 100,000 people since 1991 • Another water source: • Water begins to fill the volcano’s crater, the upper part of the crater is weak, and the lake level rises • The crater possibly collapses or overflows, emptying the lake • In 2001 a channel was dug to divert water away to reduce chances of a collapse • Lava cools and forms a layer of hard rock where no plants can grow for a while, which later breaks down to form rich soil

11. Volcanic gases and ash affect the air • Nearby a volcano: unpleasant odors from gases released from magma • Sulfur: Hydrogen sulfide gas = rotten eggs • Carbon dioxide: no color or odor • Gases released before, during, and after an eruption • Gases dangerous to breathe: lungs • In 1986, 1700 people died from a volcano at the bottom Lake Nyos releasing a massive amount of carbon dioxide • Pipes are now being used to release carbon dioxide from the bottom of the lake, preventing gases from building up

12. Lake Nyos in normal conditions (left) and just after the 1986 gas release (right). The sudden welling up of carbon dioxide from the bottom of the lake brought iron to the surface, which oxidized, creating the brown rust color.

13. ? • What are two ways a volcanic eruption can result in damage to areas hundreds of kilometers away? • Heavy ash falls or tsunamis • Why can volcanic ash be dangerous for years after an eruption? • Ash can mix with other loose materials and rainwater or floodwater to create dangerous mudflows • Describe how volcanic eruptions affect Earth’s surface • What are four kinds of events that can happen during a volcanic eruptions? • Lava flows, mudflows, pyroclastic flows, steam explosions • Explain: How do volcanic gases affect the atmosphere: How do volcanic gases aid ash in blocking sunlight? • They lift ash high above an erupting volcano where winds can spread the ash and keep it suspended in the atmosphere, so it blocks sunlight • Describe two ways sulfur dioxide can affect the atmosphere • By forming acid rain and by forming a haze that blocks sunlight

14. Volcanic activity affects water • Ex: Yellowstone National Park: hot springs • Heated water flowing to the Earth’s surface • Sit in a huge caldera • Hot spring’s heat comes from a hot spot under the North American plate

15. Hot Springs, Geysers, and Fumaroles • Hot springs are usually in areas where magma or hot rock is near Earth’s surface • Usually hot water flows into a calm pool • Geysers are a type of hot spring where water shoots into the air • Water collects in an underground chamber • It then erupts through a narrow channel • Old Faithful in Yellowstone: erupts every 35 minutes to 2 hours

16. Hot Springs, Geysers, and Fumaroles • Beneath Iceland: ocean spreading center • Magma rises as plates pull apart • Hot underground water is used as an energy source • Geothermal spa! • The steamy waters are part of a lava formation, and full of minerals such as silica and sulfur

17. Hot Springs, Geysers, and Fumaroles • Fumarole – similar to hot spring but rather than liquid water, it releases steam and other gases • Changes in hot springs and fumaroles on volcano sides indicate it may be becoming more active

18. Deep-Sea Vents • Hot springs that form at spreading centers in the ocean • Cracks in the ocean floor where cold seawater sinks to depths of several kilometers • The sea water gets heated by hot rock and magma, then rises again • This hot water is rich in dissolved minerals and gases from the rock and magma • Warm water can flow gently from cracks in the floor • Some can have higher temperatures at 350C (660F) shooting out of chimney-like vents • This water looks black because of the dissolved minerals • Vents are built up when the minerals cool and solidfy • Unusual organisms are found here: blind crabs and tubeworms up to 3 m (10 ft) long • Energy from chemicals

21. Volcanic gases and ash affect the air • Sulfur dioxide + water  acids • Can fall in rain, snow, or sleet • Rain with a large amount of acid = acid rain • Volcanoes are a source of acid rain • So are humans – coal burning • Can damage forests, kill fish • Volcanic gases can affect worldwide weather • Haze from sulfur dioxide, reducing temperatures • Ash can be lifted high above and far away from an erupting volcano • Smallest ash particles remain in the air for years