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 Pyroclastic flows
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 Steam Explosions
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