Why does a volcano erupt? What is a lahar? Why is a pyroclastic flow so dangerous? Why do people still live near volcanoes? What happened during the 1980 eruption at Mt. St. Helens? Why does Etna erupt so frequently?
The lessons covered in this unit are: 15. Volcanoes 16. Volcanic activity 17. Predicting and preparing 18. Hazards of volcanoes. 19. Benefits of volcanoes. 20. Mount St Helens, USA, 1980. 21. Mount Etna (Sicily). |
15. VOLCANOES
🡺 I can label the various features of a cross-section diagram of a volcano, including; crater, secondary or parasitic cone, lava tube, magma chamber and side vents.
🡺 I can list the main characteristics of composite cone, acid and basic lava volcanoes. How do volcanoes form?
There are two main types of volcano - composite and shield. The two types of volcano form in different places and have very different characteristics. Composite volcanoes
Shield volcanoes
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Geo-check!
1. The diagram here shows a cross-section of a volcano. Label it with the words listed below.
2. Explain why certain volcanoes have steep slopes while others have rather gentle slopes. 3. Using an atlas and your map of plate boundaries name the type of volcano you would expect to find in each of the following places (composite or shield). Give the reason why you would find that type of volcano.
4. On the right is a list of major volcanic eruptions.
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16. VOLCANIC ACTIVITY
🡺 I can classify the three main types of volcano, according to frequency of eruptions.
Volcanoes can be described in terms of activity depending on how frequently they erupt. Active volcanoes - Volcanoes that still erupt frequently
Dormant volcanoes - Volcanoes that are temporarily inactive but not fully extinct
Extinct volcanoes - Volcanoes that are never likely to erupt again
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17. PREDICTING AND PREPARING
🡺 I can describe the measures that can be taken to lessen the hazards of a volcano.
Predicting an eruption As a volcano becomes active, it gives off a number of warning signs. These warning signs are picked up by volcanologists and the volcano is monitored. Warning signs
Monitoring techniques
Preparing for a volcanic eruption A detailed plan is needed for dealing with a possible eruption. Planning for a volcanic erupti on includes:
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Geo-check!
1. Why is it important for scientist to monitor volcanoes for the following people?
2. For each of the different instruments used to monitor a volcano below, write down a. what it monitors b. the warning sign.
- Someone living near a volcano
- Tourists visiting a volcano
- An airline pilot
- Everyone on earth
2. For each of the different instruments used to monitor a volcano below, write down a. what it monitors b. the warning sign.
- Tiltmeter
- Thermal Imaging
- Seismometer
- Spectrometer
18. VOLCANIC HAZARDS
🡺 I can list and define the hazard effects of a volcano on people and the environment including volcanic gases, ash cloud, lava flow, pyroclastic flow and lahars.
Volcanoes can be exciting and fascinating, but also very dangerous. Any kind of volcano can create harmful or deadly phenomena, whether during an eruption or a period of calm. Lava Flows
Volcanic Gases
Lahars
Pyroclastic Flow
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Geo-check!
1. Eyjafjallajökull (aye -ya fyah dla jow kudl) is a volcano in Iceland. Iceland sits on a boundary where the Eurasian plate is pulling away from the North American plate. On the 20th March 2010 the volcano erupted for the first time.
On the 14th April, a new eruption occurred directly underneath the glacier. The meltwater got into the vent of the volcano creating an explosive eruption sending an ash cloud many km into the air.The diagram below shows the ash cloud at its peak. a. What hazard do you think caused most damage? b. Explain how the ash can reach far away places. c. List the types of damage the ash cloud caused to the following industries:
2. In 1985, the volcano Nevado del Ruiz erupted in central Colombia. As pyroclastic flows erupted from the volcano's crater, they melted the mountain's glaciers, sending four enormous lahars down its slopes at 60 kilometers per hour. The lahars picked up speed and coursed into the six major rivers at the base of the volcano; they engulfed the town of Armero, killing more than 20,000 people. a. Why is a lahar so dangerous? b. Why was this area so badly affected with such large lahars? c. Explain the damage a lahar can do. 3. On the 22nd August at around 1 pm Mount Vesuvius violently erupted, spewing up a high-altitude column from which ash and pumice began to fall, blanketing the area. Later on at night, pyroclastic flows in the close vicinity of the volcano began. a. What materials are in a pyroclastic flow? b. Why is a pyroclastic flow dangerous? Pliny the Younger was the Commander of the Roman Navy at the time. He wrote letters describing the event. He said: “It was daylight now elsewhere in the world, but there the darkness was darker and thicker than any night.” c. Why did he say that? What was making everywhere dark? 4. The article below is about volcanic activity near the city of Nyos in Cameroon, Africa. Fill in the blanks with the words below. Nyos red Cameroon rumbling cloud cattle consciousness died 25 Lake Nyos had long been quiet before it happened. Farmers in the West African country of _______ knew the lake as large, still and blue. But on the evening of the 21st August 1986, farmers living near the lake heard _______ . At the same time, a frothy spray shot hundreds of feet out of the lake, and a white cloud collected over the water. From the ground, the _______ grew to 100 meters tall and flowed across the land. When farmers near the lake left their houses to investigate the noise, they lost _______ . The heavy cloud sunk into a valley, which channelled it into settlements. People in the affected lost consciousness or died in a few breaths. In _______ and Kam, the first villages hit by the cloud, everyone but four inhabitants on high ground _______ . The cloud killed people up to ______ kilometres away from the lake. Over the next two days, people from surrounding areas entered the valley to find the bodies of humans and cows lying on the ground. Around 1,700 people and 3,500 _______ had died. The lake had changed, too. It was now shallower; plants and leaves floated in it; and its formerly picturesque blue hue had darkened _______ due to the iron. |
19. BENEFITS OF VOLCANOES
🡺 I can appreciate the advantages of living in volcanic areas, including, fertile soil, geothermal energy, tourism, building materials, and rich mineral deposits.
People choose to live in volcanic areas despite the risks of an eruption. Volcanoes can provide people with many benefits such as these. Fertile soil Ash ejected by the volcano acts as a good fertiliser for soils. The lava provides valuable nutrients which makes soil very fertile. Ex: Citrus and pistachios near Etna Geothermal energy Geothermal energy is where heat from within the earth is used to generate electricity. Geothermal energy can be generated in areas where magma lies close to the surface. This is good for increasing our renewable energy use. Ex: New Zealand Tourism Volcanoes attract many tourists, who enjoy the dramatic scenery that they produce. Tourism increases money to the local economy. Ex: Vesuvius, Italy Building materials Lava can be used for building houses and roads. Ex: Hawaii Rich mineral deposits Minerals are contained in lava such as diamonds, aluminium, nickel and gold. - these can be mined to make money. Items made from stone, like pumice stone can also be sold to tourists Ex: Diamonds in South Africa |
Geo-check!
1. You’ve just moved into a volcanic area. Write an email to your friend, describing all the advantages of living near a volcano. Below are some examples to help you.
- Iceland - Over 120 open-air swimming pools are heated by naturally occurring hot water. Swimming is an extremely popular pastime here.
- Etna, Sicily - Lava has weathered to produce fertile soil. This led to many people settling around the volcano, where the soils are used to grow oranges, olives, lemons, vines and nuts.
- Reykjavik, Iceland - Hot spring water is carried by pipeline to the capital city of Iceland, giving most people a cheap form of energy which does not damage the environment.
- Taupo, New Zealand - Electricity is generated from the geothermal resources of hot water which lie under the ground in the North Island of New Zealand.
- Japan - Greenhouses producing tomatoes, cucumbers and flowers are heated using geothermal energy.
- Mexico - The volcanic rocks provide good building materials. The lighter volcanic material is also mixed with cement and used in the construction industry
- Vesuvius, Naples - The dramatic scenery created by volcanic eruptions attracts thousands of tourists.
- Russia - Many rich deposits are found when lava cools e.g. copper, silver, gold, diamonds, green crystals and other gems.
- Yellowstone National Park, USA - The regular eruption of hot water and steam known as geysers are valuable tourist attractions.
20. CASE STUDY: MOUNT ST HELENS (USA), 1980.
🡺 I can identify the location of Mt St Helens on a world map.
🡺 I can explain the causes of the eruption including plate boundaries. 🡺 I can describe the course of events as well as the effects of the eruption. Why did it happen?
Primary effects
Secondary effects
Responses
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Geo-check!
1. Look at the map of Mt. St Helen.
a. On the map of America, mark:
b. On the satellite image, mark:
c. Using your knowledge of plate boundaries, explain how the volcano formed. 2. Answer these questions about the eruption event. a. What happened during the 1980 eruption? Mention the date and time. b. Find a photo from before and after the 1980 explosion. 3. List the effects of the 1980 eruption on:
4. Why do you think people still live near the volcano? 5. If you were the governor of Washington during the eruption of Mt. St. Helens what would you do? Mention at least FOUR ideas. |
21. CASE STUDY: MOUNT ETNA (ITALY)
🡺 I can locate the position of Mt. Etna in relation to the African and Eurasian plate boundaries.
🡺 I can describe the eruptions of Mt. Etna as an active volcano. 🡺 I am aware of the damage caused by some eruptions. 🡺 I can identify the advantages of the volcano to the local people Mount Etna is an active volcano in Sicily and erupts very frequently. Causes of the eruptions
Eruptions
The 2001 Eruption
Effects Human life No deaths or injuries Settlements Small hillside villages destroyed by earthquake. Hundreds of families evacuated. Communications Catania airport closed for several days. Roads covered with ash making traffic. Farming Crops were affected by heavy falls of ash. Forests Trees were destroyed by fires. Fire-crews used water from helicopters to stop it. |
Geo-check!
1. Look at this simplified tectonic map of the area around Italy.
a. What do you notice about this area?
b. Using the internet or an atlas, mark these volcanoes with a black spot.
c. Do these on the map itself:
d. What is happening to the Messina plate in between?
e. Why are there these four volcanoes in this area?
2. Why do you think so many people still live under the volcano? Give examples.
a. What do you notice about this area?
b. Using the internet or an atlas, mark these volcanoes with a black spot.
- Mount Etna
- Stromboli
- Vulcano
- Vesuvius
c. Do these on the map itself:
- Shade the African Plate and the Eurasian Plate.
- Mark the direction they are moving in.
d. What is happening to the Messina plate in between?
e. Why are there these four volcanoes in this area?
2. Why do you think so many people still live under the volcano? Give examples.