Chapter 10: Mountains and Volcanoes10.1: Movement of rock builds mountains

10.2: Volcanoes form as molten rock erupts

10.3: Volcanoes affect Earth’s land, air, and water

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

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

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

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

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

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

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

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

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.

? 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

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

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

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

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

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

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