Geography Hazards Chpater 8 Volcanoes

What is the Ring of Fire ? Where is it ?

It is where 65% of volcanoes are found. It is around the Pacific Ocean.

What is Magma vs. Lava ?

Lava is Magma but on Earth’s surface

What is Magma made of ?

Silicon and Oxygen (called silica)

What are the types of volcanic rocks ? (BADR)

Basalt → Audesite → Dacite → Rhyolite (low silicia → high silica)

Magma contains 3 gases, which are…

Water vapour, carbon dioxide, sulphur dioxide

What does the shape of a volcano depend on ?

The chemistry and viscocity of magma

High silica magma (R______ and D_______) produce…

Rhyolitic, dacitive magma produces explousive eruptions (high in silica)

What are the 4 types of volcanoes ?

Shield Volcanoes, Composite Volcanoes, Volcanic Domes, Cinder Cone Volcanoes

Shield volcanoes are… (in size)

Largest, shaped as broad ores built from lava.

Tephra is…

Produced from Shield volcano eruptions. Fragmented material blow out after eruption.

Pyroclastic deposts from Tephra form…

Pyroclastic Rock

Shield Volcanoes are most common in 3 places :

Hawaii, Iceland, around Indian Ocean

Composite Volcanoes are also known as…

Stratovolcanoes (stratified layers of lava and deposists). Cone-shaped, lava flows+pyroclastic deposits. Can cause flood due to ice melting on a mountain. More dangerous but less frequent.

Composite (stratovolcanoes) volcanoes are common in 3 Mt. Places

West coast from Alaska to Northern California. Mt. Rainier, Mt. Helens. Mt. Adams

Volcanic Domes have highly ______ magma.

Contain highly viscous rhyolite magma. Steep-sided mounds that form around vents.

Cinder cone Volcanoes are (in size) _______ and formed of ______. Common in __________

small, formed of tephra, have crater on top. Common in Mexico

Maars is (hint : water, latin)

a circular volcanic crater produced by an explosion and filled with water. Groundwater encounters magma, creating an explosion). Maar means sea in Latin.

Ice-contact volcanoes erupt where ?

Under glaciers

Floods caused by ice-contact volcanoes are known as…

jökulhaups (joe kool slaps memory trick)

Lava that contacts glacier cools it to…

Pyroclastic rock (like minecraft!)

Ice-contact volcanoes are common in

Iceland (duh), British Columbia on Mt. Garibaldi (exposed rock)

A Crater is a depression formed by explosion of volcano ______. Can be up to _______ in diameter.

A depression formed by explosion of volcano top. Can be up to 2km in diameter.

A volcanic vent is an _______ at the surface through which _____ & ________ erupt. It can either be circulat or be a side crack (called _______)

opening at the surface through which lava & pyroclastic debris erupt, can be circular or side crack (fissures)

A Caldera is a ________ (shape) ________ formed during a _______ of a volcano. Can be up to _____km in diameter. What is the danger of these ?

A Caldera is a circular / oval shape depression formed during a collapse of a volcano. Can be up to 25km in diameter. An eruption from a Caldera is the deadliest. Formed by collapse of a magma chamber below a composite volcano during explosive eruption.

Hot Springs and Geysers, what is the difference ? Where are they located ?

Hot Springs is heated groundwater. Boiled groundwater causes geysers (about 1000 on Earth). Yellowstone National Park.

What is the most famous geyser ?

Old Faithful, 50m in height. Lasts of 2-3 minutes. 70min intervals

What is a super eruption ?

Products of supervolcanoes, very rare. Large volume of magma rises to shallow depth in continental crust over a hot spot. The Crust will usually contain it, but if the pressure is too high, it breaks and creates ash falls.

What is the National park on top of Caldera that formed from an eruption called ?

Yellowstone National Park, Supervolcano. Earthquakes in this park are monitored. Millions of people would die from ash suffocation from a super eruption, and agriculture would suffer.

Along with geysers, what else is common in the Yellowstone National Park ?

Many species of wildlife

Where can volcanoes be found in Canada ?

British Columbia and Southern Yukon

What Volcano poses the biggest risk to Canada and where is it located ?

Mt. Baker in Washington. If it erupts, it would ash over B.C. Also would cause landslides from ice melting and floods.

How many volcanoes erupt each year ? How many people died from volcanoes in the past 2 centuries ?

50-60. Over the past 2 centuries, over 100,000 people died from eruptions.

Climatic Effects of Volcanoes. Ash & Gases reflect solar radiation, which causes _______.

Cooling

The 2 mountains/volcanoes that caused cooling are…

Mt. Tambora (in Indoneisa), Year without summer in 1816. Mt Pinatubo (Philippines), was one of the coolest years worldwide.

Lava flows…

Magma flows out of central crater or fissure along side of a volcano

Liquidy, low viscosity (smooth), high temperature, smooth rock texture is ______ lava

Pahoehoe basaltic lava

High viscosity (thick), lower temperature, blocky rock texture is _________ lava

Aa basaltic lava

Avalanche of ash gas, rock fragments that travel down the slopes of a volcano during eruption is named… Most people die from this part.

Pyroclastic Flow

Particles of ash can be buried downwind hundreds of km from eruption site is called…

Ash Fall

What are the impacts of Ash Fall ?

Destroys vegetation, contaminates surface water, health impacts to people & animals, causes aircraft engine failure.

What are some poisonous gases from eruptions ?

Sulphur diocide can burn holes in leaves and form acid precipitation.

What is ‘‘Vog’’ ?

A smog that can cause asthma attacks and respiratory problems. Also high amounts of Co2 can kill animals.

What is a Sector Collapse ?

A flank of volcano collapses, forms bulge where slopes are too steep.

Lahar ADA mudflows

Are large amounts of material that has become saturated with water and moves downslope. Indonesian word

What happened to Mt. St. Hellens ?

Small explosions caused a bulge. Lateral blast, ash travelled around the world, 57 people died, now feforeting barren landscape

What are some natural service functions of volcanoes ?

Ancient volcanoes provided the gases that now form protective layer on Earth in the atmosphere. Internal heat from volcanoes can produce renewable geothermal energy. Volcanic landscapes attract tourism & recreation. Eruptions created new land (Hawaii, Iceland)

Minimizing the Volcanic Hazard, what is a forecast ?

A probability that a volcano will erupt within a given time

What 5 steps are used to forecast volcanoes ?

1. Monitoring seismic activity (shallow earthquakes can precede eruptions, short warning times from this information are a concern).

2. Thermal and hydrologic monitoring (accumulation of magma changes properties of rock and soil, increased heat may melt snow or glaciers above

3. Land surface monitoring (involving checking for the growth of bulges, swelling, opening of cracks)

4. Monitoring volcanic gas emissions (increases in co2 or sulphure may indicate magma is moving towards the surface)

5. Analyzing the local geological history (mapping of volcanic rocks, dating of pyroclastic deposits)