Volcanoes - Questions & Answers

EXERCISES

I. Choose the correct option:

1. The forces arising from the interior of the earth:
(a) Endogenic forces   (b) Exogenic forces   (c) Platonic forces   (d) Interior forces
Answer: (a) Endogenic forces

2. A vent in the earth's crust from which fiery hot magma erupts from the earth's interior:
(a) Plate   (b) Tectonics   (c) Volcano   (d) Vent
Answer: (c) Volcano

3. Which of the following is NOT a cause of volcanic eruptions?
(a) Heat from the sun   (b) Plate Tectonics   (c) Magma chamber   (d) Heat and pressure inside the earth
Answer: (a) Heat from the sun

4. Which amongst the following is NOT a product of volcano?
(a) Magma   (b) Lava   (c) Solid Matter   (d) Vent
Answer: (d) Vent

5. During repeated eruptions the summit of a volcano may be blown up leaving a large depression called:
(a) Caldera   (b) Hot springs   (c) Geysers   (d) Circum belt
Answer: (a) Caldera

6. Assertion (A): Most volcanic eruptions take place near plate margins.
Reason (R): When these plates slide past each other or collide against each other due to intense heat inside the earth's core, their edges produce faults along the lines of weakness.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R does not explain A.
(c) A is true but R is false.
(d) A is false but R is true.
Answer: (a) Both A and R are true and R is the correct explanation of A.

7. (c) Geysers is a fountain of hot water and steam that escapes when underground water comes into contact with hot volcanic rocks.
(a) Caldera   (b) Hot springs   (c) Geysers   (d) Volcano

8. Which of the following is incorrect?
(a) Extinct Volcano: Mt. Kenya   (b) Dormant Volcano: Mt. Kilimanjaro   (c) Extinct Volcano: Mt. Etna   (d) Active Volcano: Mt. Stromboli
Answer: (c) Extinct Volcano: Mt. Etna

9. Assertion (A): Steam is the most abundant gas that comes out of a volcano.
Reason (R): Violent eruptions, known as bombs, eject materials varying in size.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R does not explain A.
(c) A is true but R is false.
(d) A is false but R is true.
Answer: (b) Both A and R are true but R does not explain A.

10. Which of the following is NOT a constructive effect of volcanoes?
(a) Landform formation   (b) Tsunami   (c) Geothermal energy   (d) Tourism
Answer: (b) Tsunami

11. The volcanoes that occur near Earthquake belts and tectonic plate boundaries:
(a) Caldera   (b) Geysers   (c) Pacific ring of fire   (d) Mid-world mountain belt
Answer: (c) Pacific ring of fire

12. Mt. Vesuvius, Mt. Etna are located in the:
(a) Circum Pacific belt   (b) Mid-world Mountain Belt   (c) Pacific Ring of fire   (d) None of the above
Answer: (b) Mid-world Mountain Belt

13. (a) Hot springs are also known as Thermal Springs.
(a) Hot springs   (b) Geysers   (c) Volcano   (d) Caldera

14. Assertion (A): The lava and ash deposited during an eruption breaks down to provide valuable nutrients for the soil and thus create fertile soil.
Reason (R): Agricultural fields are covered with layers of volcanic ash and dust making them unsuitable for cultivation.
(a) Both A and R are true and R is the correct explanation of A.
(b) Both A and R are true but R does not explain A.
(c) A is true but R is false.
(d) A is false but R is true.
Answer: (b) Both A and R are true but R does not explain A.

II. Short Answer Questions

1. The area marked brown colour on the map given alongside is referred to as the Pacific Ring of Fire. Why is it so called?
Answer: The Circum Pacific Belt is called the Pacific Ring of Fire because over 80% of the total number of active volcanoes are concentrated in this region, which is located near earthquake belts around the young fold mountains.

2. What is a volcano? Give one example.
Answer: A volcano is a vent in the earth's crust from which fiery hot magma erupts from the earth's interior. An example is Mt. Etna in Italy.

3. What is the difference between magma and lava?
Answer: The molten rock material inside the earth is known as magma. When this molten rock reaches the surface of the earth, it is known as lava.

4. Give one example each of an active volcano and a dormant volcano.
Answer: An example of an active volcano is Mt. Stromboli in Italy. An example of a dormant volcano is Mt. Kilimanjaro of Africa.

5. What is the difference between dormant volcano and an extinct volcano?
Answer: Dormant volcanoes have not erupted in the recent historical period but are regarded as 'sleeping' and may become active at any time. Extinct volcanoes have not erupted in the present geological period and are highly unlikely to become active again.

6. What is the magma chamber of a volcano? State the products erupted by a volcano.
Answer: A magma chamber is a huge underground reservoir created when molten material melts weak rocks and collects while still under the earth's crust. The products erupted by a volcano include magma and lava, gases (like steam, hydrogen sulphide, sulphur dioxide, carbon dioxide, and hydrogen), and solid matter (such as pyroclasts, dust, lapilli, and bombs).

7. Name two types of landforms made by volcanoes. Give an example of each type.
Answer: 1. Volcanic Plateaus: e.g., Plateau of Peninsular India. 2. Volcanic Mountains: e.g., Mt. Fuji in Japan.

III. Structured Questions

1. (a) Describe the two causes of volcanic eruptions.
Answer: The two main causes are: (i) Heat and Pressure inside the Earth: Temperature and pressure increase towards the centre of the earth, melting rocks and building immense pressure that forces the heat to find an escape route through fissures. (ii) Plate Tectonics: When movable plates of the earth's crust slide past or collide with each other due to intense internal heat, they produce faults along lines of weakness, allowing hot magma to gush out.

1. (b) Describe two types of volcanoes, giving an example of each type.
Answer: (i) Active Volcanoes: These are presently in an active state and have erupted in the recent past (e.g., Mt. Stromboli in Italy). (ii) Extinct Volcanoes: These have not erupted in the present geological period and are not likely to become active again (e.g., Mt. Aconcagua in South America).

1. (c) Give a geographical reason for each of the following:
(i) Many volcanoes are found along plate boundaries.
Answer: Because when tectonic plates slide past or collide against each other, their edges produce faults along lines of weakness, which provides an escape route for magma.
(ii) Volcanic mountains are the most diverse mountains in the world.
Answer: Because there are great differences in the nature of volcanic eruptions as well as the variety of materials they throw up to build the mountains.
(iii) Hot springs have medicinal properties to cure skin diseases.
Answer: Because they contain many dissolved minerals, particularly being a rich source of sulphur, which is considered highly beneficial for curing skin diseases.

1. (d) Draw a well labelled diagram showing the different parts of a volcano and the products erupted by it.
Answer: [Drawing activity: Students should draw a volcano diagram labelling the Magma Chamber, Central Conduit Channel, Vent, Volcanic Cone, Solidified lava and ash layers, Smoke, Steam, Eruption of Lava, and Pyroclastic material.]

2. (a) Explain briefly the landforms created by volcanoes on the surface of the earth.
Answer: Extrusive landforms created on the earth's surface include Volcanic Plateaus (derived from extensive lava flows, like the Plateau of Peninsular India), Volcanic Mountains (built from materials ejected from fissures, like Mt. Fuji), and Volcanic Plains (vast and smooth areas formed by extensive volcanic flooding, like the Western Victorian Plains in Australia).

2. (b) Write any three destructive effects of volcanoes.
Answer: 1. Erupting volcanoes and hot lava destroy human, animal, and plant life, as well as property. 2. Huge clouds formed after the eruption cause heavy rains that result in deadly floods and landslides. 3. They emit poisonous gases that pollute the environment and cause severe health problems.

2. (c) Explain the following terms:
(i) Volcanic Cone
Answer: The typical cone-like shape formed when erupted fluid material cools gradually and solidifies around the vent of a volcano.
(ii) Caldera
Answer: A large depression formed when the summit of a volcano is blown up or collapses due to repeated eruptions.
(iii) Geyser
Answer: A fountain of hot water and steam that escapes forcefully when underground water comes into contact with hot volcanic rocks.

2. (d) Describe world distribution of volcanoes.
Answer: Volcanoes are primarily located in two important zones: 1. The Circum Pacific Belt (Pacific Ring of Fire), situated near earthquake belts around young fold mountains. Over 80% of active volcanoes are located here (e.g., Andes, Philippines, Japan). 2. The Mid-world Mountain Belt, which includes renowned volcanoes like Mt. Vesuvius, Mt. Etna, and Mt. Stromboli.

IV. Thinking Skills

1. Imagine that you had gone for a holiday and an extinct volcano erupted. List the consequences.
Answer: Since no preparations would be in place for an extinct volcano, an unexpected eruption would cause extreme panic and massive destruction. The consequences would include loss of life and property due to sudden lava flows, extensive damage to the local environment and agriculture from thick layers of volcanic ash, heavy air pollution from poisonous gases leading to respiratory distress, potential floods and landslides, and a complete halt to transport, tourism, and daily life.

2. Suppose you are living in an area known for volcanic eruptions. One day, when you were sitting in your balcony, you suddenly noticed a volcano erupting at a distance. State what happened thereafter.
Answer: Immediately after noticing the eruption, I would see huge clouds of smoke, steam, and ash billowing into the sky, likely followed by loud explosions. The sky would begin to darken. Lava might visibly start flowing down the volcano's slopes. Soon, volcanic ash would start falling over my area, and the air would smell of sulfur. Local authorities would issue emergency sirens and evacuation orders, prompting everyone in the vicinity to quickly move to safer, designated zones to escape the poisonous gases, advancing lava, and secondary threats like landslides.

V. Map Work/Project

1. Using your knowledge of chemistry make a model of a volcano to study the extent of damage that can be caused by a volcanic eruption. Extrapolate your calculations to predict the energy released during the last few volcanic eruptions.
Answer: [Practical Project: Students can build a volcano model using common craft materials and use a mixture of baking soda and vinegar to simulate an eruption. Predicting real-world volcanic energy requires referencing advanced geological data from volcanic observatories.]

2. Recently there was a news article regarding the closure of Manila's International airport following a major volcanic eruption of the Taal Volcano. On the map of the world locate the Taal Volcano. What inference do you draw from the location of the volcano? Correlate your findings with news articles of the eruption. Make a list of potential eruption prone volcanoes that could cause closure of international airports in other countries. Mark them on an outline map of the world.
Answer: [Map Work/Research Project: Students should locate the Taal Volcano in the Philippines on a world map. The inference is that its location is within the highly active Circum Pacific Belt (Pacific Ring of Fire), making it highly prone to explosive eruptions that eject massive ash columns into commercial flight paths. Other eruption-prone volcanoes that could close international airports include Mt. Merapi in Indonesia, Mt. Fuji in Japan, and Mt. Vesuvius in Italy, which students should then plot on their outline maps.]