Selina Concise Solutions for ICSE Class 9 Geography Chapter 7 Volcanoes

Exercises

I. Short Answer Questions.

Question 1: What are known as volcanoes ?
Answer: Volcanoes are the vents in the earth’s crust erupting hot magma from the interior core motivated by endogenic forces.
Volcanoes act as natural safety valves for our planet, releasing incredible pressure built up deep underground. They are shaped like mountains but have a special opening that connects the surface to the molten heart of the Earth.
Teacher's Tip: Think of a volcano like a boiling pot of soup with a lid; when the pressure gets too high, the soup pushes the lid up and spills over!
Exam Tip: Always use the term "endogenic forces" to explain what motivates the eruption for a higher score.

Question 2: What is the difference between magma and lava ?
Answer: Molten material moving under the earth’s crust is called magma. When magma comes to the surface of the earth it is known as lava.
The main difference is simply where the liquid rock is located. It is "magma" while it is hidden in the dark tunnels underground and becomes "lava" the moment it sees the light of day.
Teacher's Tip: Remember: Magma is Midway (underground) and Lava is Land-side (on the surface).
Exam Tip: Clearly state the location (underground vs. surface) to define these two terms correctly.

Question 3: Give one example each of an active volcano and a dormant volcano.
Answer: Active Volcano - Mt. Stromboli and Mt. Etna in Italy
Dormant Volcano - Mt. Kilimanjaro of Africa.
An active volcano is one that erupts frequently, while a dormant volcano is like a sleeping giant that hasn't erupted for a long time but could wake up. Mt. Kilimanjaro is a famous example of a peaceful-looking mountain that is actually a dormant volcano.
Teacher's Tip: Think of "Active" as "Awake" and "Dormant" as "Dormir" (to sleep in French).
Exam Tip: Make sure to mention the country or continent for your examples to show complete knowledge.

Question 4: What is the difference between dormant volcano and an extinct volcano ?
Answer: Dormant volcano can erupt at any interval but extinct volcano can never erupt again.
A dormant volcano is "sleeping" and might wake up to erupt in the future. An extinct volcano is "dead" because its supply of hot magma has been cut off forever, meaning it will never explode again.
Teacher's Tip: A dormant volcano is like a light that is turned off but still plugged in, while an extinct volcano is like a light with its wires cut!
Exam Tip: Use the words "likelihood of future eruption" to distinguish between these two types.

Question 5: What is the magma chamber of a volcano ?
Answer: The magma chamber is created by the molten magma itself by melting the surrounding rocks in the form of a huge chamber.
This is a giant underground reservoir or "pool" where liquid rock collects before an eruption. The intense heat of the magma is so strong that it actually carves out this space by melting the solid rocks around it.
Teacher's Tip: Imagine the magma chamber as a giant balloon filled with liquid fire, waiting for the right moment to pop.
Exam Tip: Describe it as a "source" or "reservoir" located deep in the crust.

Question 6: Name two types of landforms made by volcanoes.
Answer: Two types of landforms are :
1. Extrusive landforms : Extrusive landforms include crater composite cones caldere lava platforms.
2. Intrusive landforms : Intrusive landforms include dykes batholiths laccoliths volcanic hill etc.
Extrusive landforms are shapes we see on the outside of the Earth, like volcanic peaks. Intrusive landforms are shapes made by magma that got stuck and hardened inside the Earth's crust without ever coming out.
Teacher's Tip: "Ex" means Exit (outside), and "In" means Inside.
Exam Tip: List at least two examples for both extrusive and intrusive types to get full marks.

Question 7: What is called the Pacific Ring of Fire ? Why is it called so ?
Answer: There are 80% active volcanoes around the Pacific ocean which is called the Ring of Fire.
This area is a giant horseshoe-shaped belt that circles the Pacific Ocean where most of the world's volcanic eruptions and earthquakes happen. It is called the "Ring of Fire" because it literally looks like a glowing circle of active volcanoes on a map.
Teacher's Tip: Imagine the Pacific Ocean as a giant bowl, and the edges of the bowl are lined with fiery volcanoes!
Exam Tip: Remember the statistic "80%" and link it specifically to the "Pacific Ocean."

Question 8: Name the three types of volcanoes on the basis of the frequency of their eruption.
Answer: There are three types of volcanoes e.g. active volcano which is still active in erupting magma dormant volcano which erupts in uncertain intervals and extinct volcano which has stopped eruption permanently it is also called dead volcano.
Volcanoes are classified by how often they "blow their tops" or show signs of life. This helps scientists understand which ones are dangerous today and which ones are safe to live near.
Teacher's Tip: Active = Awake, Dormant = Sleeping, Extinct = Dead.
Exam Tip: Use the term "frequency" in your answer to show you are answering the specific question asked.

Question 9: What are known as Shield volcanoes ?
Answer: A volcanoes erupting with plentiful lava spreading over the surface into several kilometres with huge circumference and taking a shape of shield are called as shield volcanoes.
Shield volcanoes are wide and broad with gentle slopes because the lava they release is very thin and runny, like syrup. Instead of a tall peak, they look like a warrior's shield lying flat on the ground.
Teacher's Tip: Think of a "Shield" as being broad and flat, not tall and pointy.
Exam Tip: Mention the "gentle slope" and "runny lava" to describe a shield volcano correctly.

Question 10: Mention any two extrusive landforms caused by volcanic eruptions.
Answer: 1. Composite cone : The volcano which erupts both lava and pyroclastic rocks form alternating layers of these two materials and build up to form composite cones. Examples : Fujiyama in Japan Vesuvius and Stromboli in Italy.
2. Caldera : During repeated eruptions the summit of a valcano may be blown up. In its place a large depression called caldera is formed. These are generally formed when the magma chamber is no longer able to emit sufficient magma and results in the collapse of a cone either partly or wholly.
Composite cones are the "classic" tall, beautiful volcanoes you see in pictures, made of layers of ash and lava. A caldera is a giant hole left behind when a volcano literally explodes or caves in on itself.
Teacher's Tip: "Composite" means made of many parts (layers), and "Caldera" is like a giant cauldron or pot.
Exam Tip: Providing examples like "Mt. Fuji" for composite cones makes your answer stand out.

Question 11: Name any two intrusive landforms made by volcanic eruptions.
Answer: 1. Batholiths : Large sized intrusions in igenous rocks. They occur at considerable depth and come to the surface in course of mountain building activity.
2. Laccolith : These are formed when magma spreads laterally in a dome shape. The dome also forces the overlying strata to bulge upward. The projecting landform is subjected to erosion and denudation. Thus laccolith comes to the surface.
Intrusive landforms are like hidden sculptures made of rock inside the Earth. A batholith is a massive underground base, while a laccolith is a smaller, mushroom-shaped bump that pushes the ground above it up.
Teacher's Tip: Batholiths are "Big" and "Bottom" layers. Laccoliths look like "Lentils" or small domes.
Exam Tip: Explain that these are only visible today because the top layers of soil were washed away by "erosion."

Question 12: How are hot springs formed ?
Answer: The movement of magma heats up the underground water which converts into steam and gushes out through any crack or holes on the crust.
Hot springs are like Earth's natural heated swimming pools. When water deep underground touches hot volcanic rocks, it boils and rises back up through cracks to the surface.
Teacher's Tip: Think of a hot spring like a kettle on a stove; the magma is the stove, and the spring is the steam coming out.
Exam Tip: Mention that the "heating of underground water" is the primary cause.

Question 13: What is called the Pacific Ring of Fire ? Why is it called so ?
Answer: There are 80% active volcanoes around the Pacific ocean which is called the Ring of Fire.
(See Question 7 for Extension and Tips).
Teacher's Tip: Remember it is a "Ring" because it goes all the way around the ocean's edge.
Exam Tip: Focus on the concentration of "active" volcanoes in this specific zone.

Question 14: Give an example each of conical volcano and fissure volcano.
Answer: Mount Fuji in Japan is a conical volcano and Columbia plateau in South America and Deccan plateau in India are the examples of fissure volcanoes.
A conical volcano has one main pipe and looks like a triangle. A fissure volcano happens when lava leaks out of a long crack in the ground, creating wide, flat areas instead of a peak.
Teacher's Tip: Conical = Cone (like an ice cream cone), Fissure = Fence-line or long crack.
Exam Tip: Use the "Deccan Plateau" as your primary example for fissure eruptions in India.

Question 15: What is the difference between dormant volcano and an extinct volcano ?
Answer: Dormant volcano can erupt at any interval but extinct volcano can never erupt again.
(See Question 4 for Extension and Tips).
Teacher's Tip: Dormant is "Maybe," Extinct is "Never."
Exam Tip: Contrast the "potential for future eruption" in your explanation.

II. Match the following
Column A - Column B
1. Vent - (a) An active volcano.
2. Extinct Volcano - (b) Hot water fountain.
3. Geyser - (c) Dead Volcano.
4. Mt. Stromboli - (d) An opening in the earth’s crust through which lava flow
5. Cinder cone - (e) A volcanic landform.
Answer:
1. Vent - (d) An opening in the earth’s crust through which lava flow
2. Extinct Volcano - (c) Dead Volcano.
3. Geyser - (b) Hot water fountain.
4. Mt. Stromboli - (a) An active volcano.
5. Cinder cone - (e) A volcanic landform.
This matching exercise helps you identify the different parts of a volcano and specific examples from around the world. Knowing that a geyser is a "hot fountain" and a vent is an "opening" is basic volcanic vocabulary.
Teacher's Tip: Use Mt. Stromboli to remember "Active" because it glows so much it's called the "Lighthouse of the Mediterranean!"
Exam Tip: Draw lines carefully or write the numbers and letters clearly to avoid confusion.

III. Fill in the blanks below
Answer:
1. The forces arising from the interior of the earth are called endogenic forces.
2. The molten rock that reaches the surface of the earth is called magma. (Note: Should be lava once it reaches the surface, but verbatim from text).
3. A lava shield is made up of basic lava flows solidified away from the vent.
4. Vents are intrusions of igneous rock that are vertical in shape.
5. The Circum-Paciflc Belt is also called Pacific Ring of Fire.
These blanks highlight the key vocabulary of the chapter. Understanding that forces from inside are "endogenic" and the runny lava makes "shields" is essential for your studies.
Teacher's Tip: Remember: Endogenic means Inside the Earth!
Exam Tip: Double-check "Lava" vs "Magma" in fill-in-the-blank questions based on whether it is above or below ground.

IV. Long Answer Questions

Question 1: Explain the various parts of a volcano.
Answer: A volcano represents some typical parts e.g. the molten rock or magma mostly lava makes the conical body of a volcano. Magma chamber is the source of erupting magma. Vent is the main channel through which the magma erupts outwards. Crater is the mouth or uppermost part of a volcano which is a big hole from which magma erupts and spreads all over.
A volcano is like a complicated plumbing system for hot rock. It starts with a pool at the bottom (magma chamber), goes up a pipe (vent), and comes out of the bowl at the top (crater).
Teacher's Tip: Think of the magma chamber as the basement, the vent as the stairs, and the crater as the front door!
Exam Tip: Drawing a simple diagram with these four parts labeled will help you get full marks on this long answer.

Question 2: Describe the causes of volcanic eruptions.
Answer: The main causes of volcanic eruptions are the following :
1. Heat and Pressure inside the Earth : Temperature and pressure both increase from the surface towards the centre of the earth. Rocks are bad conductors of heat. So the earth’s heat does not escape on its own. Instead it melts the rocks and builds up great pressure. The pressure forces the heat to find an escape route through fissures and cracks in the rocks.
2. Plate Tectonics : Most volcanic eruptions take place near plate margins. The same forces that cause earthquakes also cause volcanic eruptions.
3. Magma Chamber : The molten material while still under the earth’s crust melts weak rocks and creates a huge chamber for itself. Fresh magma continues to pour inside the chamber. Since magma contains silicate materials gases and water vapours the pressure always acts vertically upwards. Once a route is found it rises to the surface.
Volcanoes happen because the Earth is hot and crowded inside. This heat turns rock into a pressurized gas-filled soup that has to escape, just like steam escaping from a pressure cooker.
Teacher's Tip: Remember the three P's: Pressure, Plates, and Pools (Magma Chambers).
Exam Tip: Mention "Plate Tectonics" as it is the most important modern scientific explanation for where volcanoes form.

Question 3: Explain briefly the landforms created by volcanoes on the surface of the earth.
Answer: The landforms created on earth’s surface are called Extrusive Landforms. These include volcanic plateaus volcanic mountains and volcanic plains.
(a) Volcanic Plateaus : These are derived from lava which flows from volcanic eruptions. The Plateau of Peninsular India especially the north western Deccan is an example of lava plateau. Other examples are South African plateau Columbian Plateau and Ethiopian plateau.
(b) Volcanic Mountains : These mountains are built from material ejected from the fissures in the earth’s crust. Volcanic mountains are the most diverse because there are great differences in volcanic eruptions as well as the materials they throw up.
(c) Volcanic Plains : These plains are vast and smooth formed by extensive volcanic flooding from volcanic centres. The Western Victorian Plains in Victoria Australia are the finest examples of Volcanic Plains.
Volcanic activity creates a variety of landscapes depending on how the lava flows. If it piles up high, it makes a mountain; if it spreads out wide, it makes a plateau or a flat plain.
Teacher's Tip: Think of it as "High, Middle, and Low": Mountains are high, Plateaus are middle-high, and Plains are low and flat.
Exam Tip: Be sure to distinguish between "Volcanic Plateaus" and "Volcanic Plains" by mentioning the "flooding" vs "flowing" of lava.

Question 4: Write any three destructive effects of volcanoes.
Answer: Destructive Effects :
1. When the volcanoes erupt they destroy life and property. The hot lava together with ash and dust destroy not only human beings but also animals as well as plant life.
2. Agricultural fields are covered with layers of volcanic ash and dust making them unsuitable for cultivation.
3. Huge clouds are formed after the eruption of volcanoes causing heavy rains which result in floods and landslides.
4. Volcanoes also emit poisonous gases which pollute the environment and cause health problems.
5. Explosive volcanoes in ocean islands are followed ‘by high Tsunami waves. They flood the area and destroy property people animals and crops.
Volcanoes can be very dangerous because they don't just erupt lava, but also ash that chokes plants and gases that are bad to breathe. They can even cause giant ocean waves called Tsunamis that flood entire cities.
Teacher's Tip: Think of a volcano's destruction as a "Combo": Lava, Ash, Gas, and Waves!
Exam Tip: If asked for three, choose the most distinct ones like "Lava damage," "Poisonous gases," and "Tsunamis."

Question 5: Describe the distribution of volcanoes in the world.
Answer: Volcanoes are found along the weak zones of the earth’s crust where due to continuous tussle by tectonic forces maximum active volcanoes have created. These are
1. Cirum-Pacific Belt : It is also known as ‘ring of fire due to consisting 75 % active volcanoes of the world.
2. Mid-World Mountain Belt or Mid Continental Belt : It extends along the fold mountain zone of Alpine-Himalayan Region. Although this belt is noted for drastic earthquake but these are some of the very destructive volcanoes e.g. Stromboli Vesuvius Mt. Etna Mt. Pelee (West Indies). Out of these belts there are also various volcanoes scattered here and there.
Volcanoes aren't just placed randomly; they follow the lines where Earth's giant crustal plates are pushing against each other. Most of them are found in a big circle around the Pacific Ocean or in a line through Europe and Asia.
Teacher's Tip: Think of the distribution as a "Map of the Cracks" in the Earth's shell.
Exam Tip: Be sure to mention the name "Alpine-Himalayan Region" when talking about the Mid-World belt.

Question 6: Describe important volcanic landforms on earth.
Answer: Prominent landforms associated with volcanoes are composite cones built of multiple material erupted out from a volcano. Conical hills are common in volcanic areas Crater lake is formed along the mouth of a conical volcano which is filled with water after cooling down of volcano. Due to repeated eruptions mouth of a volcano is converted into a large depression called caldera. Lavashields are made by large amount of basic lava flows making volcanic shields with a gentle slope.
Lava plateau : is formed by large scale fissure eruptions covering extensive area e.g Columbia plateau in South America and Deccan plateau of India.
These landforms are the "fingerprints" left behind by eruptions. From beautiful blue crater lakes to the wide lava plateaus of India, volcanoes have shaped much of the land we walk on.
Teacher's Tip: A "Crater Lake" is a mountain with a pond in its mouth!
Exam Tip: Use the term "Composite cone" to describe volcanoes with layers of different materials.

Practice Questions (Solved)

Question 1: Name three causes of volcanic eruptions.
Answer:
• Hot interior of the Earth
• Steam and gases
• Faults and fissures.
Volcanoes are caused by the extreme heat inside our planet turning rock into liquid. This liquid rock and trapped steam then push through cracks (fissures) in the ground until they burst out.
Teacher's Tip: Remember: Heat + Gas + Cracks = Eruption!
Exam Tip: "Faults and fissures" is a key phrase to use for describing cracks in the crust.

Question 2: Name the largest active volcano in the world.
Answer: Mauna Loa (Hawaii islands).
Mauna Loa is a giant shield volcano that covers half of the island of Hawaii. It is so heavy that it actually pushes down the ocean floor beneath it!
Teacher's Tip: Think of "Mauna" as "Mountain" and "Loa" as "Long" (it is a very long, wide mountain).
Exam Tip: Don't forget to mention that it is in the "Hawaii islands."

Question 3: Which volcano is known as the ‘light house of the Mediterranean ?
Answer: Stromboli.
Stromboli is an active volcano that has been erupting almost constantly for thousands of years. Sailors in ancient times used its glowing red lava at night to help guide their ships, just like a lighthouse.
Teacher's Tip: Think of "Stromboli" as the "Strobe light" of the sea!
Exam Tip: This is a very common one-word answer question; memorize the spelling "Stromboli."

Question 4: Name the three belts where volcanoes are found.
Answer:
• Circum Pacific belt
• Mid-world mountain belt
• African rift valley.
Most volcanoes are found in these three specific zones where the Earth's crust is weak or breaking apart. The Circum-Pacific belt is the most famous because it contains so many active volcanoes.
Teacher's Tip: Imagine the world's volcanoes as being organized into three giant "parades."
Exam Tip: Listing all three belts correctly shows that you understand global geography.

Question 5: In which belt most of the volcanoes of the world are found ?
Answer: Circum Pacific Belt.
This belt contains about three-quarters of all the active volcanoes on Earth. It is the busiest volcanic "highway" in the world!
Teacher's Tip: "Circum" means around - so it's the belt *around* the Pacific.
Exam Tip: Use the term "Ring of Fire" as a synonym for the Circum Pacific Belt.

Question 6: Name three causes of Earthquakes.
Answer:
• Volcanic eruptions
• Tectonic causes
• Elasticity of Rocks
Earthquakes can happen when a volcano explodes, when giant plates of the Earth slide against each other, or even when rock layers "snap" back into place after being bent.
Teacher's Tip: Think of an earthquake as the Earth's crust having a sudden "shiver" or "snap."
Exam Tip: "Tectonic causes" refers to the movement of Earth's large crustal plates.

Question 7: What is epicentre ?
Answer: The point on Earth’s surface vertically above the focus is called epicentre.
The "focus" is where the earthquake starts deep underground, but the "epicentre" is the spot on the map right above it where people feel the strongest shaking. If you are standing on the epicentre, you are right in the middle of the earthquake's power.
Teacher's Tip: "Epi" means "upon" - so it's the spot *upon* the Earth's skin above the focus.
Exam Tip: Always contrast the epicentre (on the surface) with the focus (underground).

Question 8: Indicate the world distribution of active volcanoes.
Answer: There are about 500 active volcanoes. Most of them are confined to Circum-Pacific Belt and Mid World Mountain Belt.
Active volcanoes are mostly found in two major zones that follow the edges of tectonic plates. These 500 volcanoes are the ones most likely to erupt and change our world today.
Teacher's Tip: Imagine 500 red dots on a world map, mostly forming a giant circle and a line through the middle.
Exam Tip: Knowing the approximate number "500" shows you have studied the details.

Question 9: Give two reasons why tremors occur inside the earth?
Answer: 1. Movements of the earth’s crust along lines of weakness produces great tremors.
2. During volcanic activity movement of lava beneath the crust also causes tremors inside the earth.
Tremors or "shaking" happen because the ground is either breaking along old cracks or because a giant underground river of liquid fire (lava) is pushing its way through the rocks.
Teacher's Tip: Tremors are like the "rumbling stomach" of the Earth when something is moving inside!
Exam Tip: Use the term "lines of weakness" to describe the cracks where movement happens.

Question 10: Distinguish between :
1. Seismology and Volcanology.
2. Volcanic Dust and Volcanic Ash.
Answer: 1. Seismology and Volcanology : Seismology is the science of study of earthquake and Volcanology is the science of study of volcanic phenomena.
2. Volcanic Dust and Volcanic Ash : The finely pulverised fragments of rock are called volcanic ash and very fine particles which blow into air are called volcanic dust.
Seismology and Volcanology are two different "doctor" specialties for the Earth. Ash is like the coarse sand of a volcano, while dust is the super-fine powder that can float in the air for years.
Teacher's Tip: Seismology is for Shaking (quakes) and Volcanology is for Volcanoes.
Exam Tip: Define both terms in your answer to show the contrast clearly.

Question 11: Describe the materials thrown out during volcanic eruption.
Answer: The materials thrown out of a volcano due to eruptions are of three types :
1. Solid materials :- The solid materials include large fragments of rocks known as volcanic Bombs. The finest particles include cinder volcanic ash dust.
2. Liquid materials :- The liquid materials include basic lava and Acid lava. Acid lava has more silica while Basic lava has low content of Silica.
3. Gaseous materials :- The gaseous material is mainly composed of steam. The other gases include Oxygen Hydrogen Sulphuric acid Carbon dioxide etc.
A volcano is like a messy kitchen that throws out solid "bombs" of rock, liquid lava "soup," and clouds of gas "steam." Each of these materials can be dangerous in different ways.
Teacher's Tip: Remember: Solid, Liquid, and Gas - a volcano has them all!
Exam Tip: Be sure to mention "Silica" when explaining the difference between types of lava.

Question 12: Describe the effect of volcanic eruption of Karakatoa in 1883.
Answer: Karakatoa island is situated between the islands of Java and Sumatra in the Sunda strait. It suddenly erupted in 1883. The top of the mountain was blown away by the explosion 16 metres high tidal waves were caused killing 36,000 persons in west Java. Volcanic dust rose to a height of about 27 kilometres. This dust encircled the globe for 3 years. Its effect caused strange sunrise and sunset conditions.
Krakatoa was one of the loudest and most destructive explosions in history. It was so powerful that it created giant waves and put so much dust in the sky that people all over the world saw purple and green sunsets for three whole years!
Teacher's Tip: Krakatoa was the "Big Bang" of the 19th century!
Exam Tip: Mention the "tidal waves" and the "three years of dust" as the two most important consequences.

Question 13: Why is volcanic activity often associated with mountain building ?
Answer: Most of the active volcanoes are formed along the fold mountains such as the Himalayas, The Alps, The Andes etc. Fold mountains have been formed by mountain building movements. These involve intense folding and faulting which mark lines of weakness on the surface. Most of the eruptions take place along these lines of weak.
Volcanoes and mountains go together because they are both created when the Earth's crust is squashed and broken. The cracks made during mountain building act like "easy exits" for magma to escape to the surface.
Teacher's Tip: Think of it this way: where the Earth's crust is "folding" into mountains, it is also "cracking" into volcanoes.
Exam Tip: Use the term "lines of weakness" to explain why magma chooses certain spots to erupt.

Question 14: Describe the materials thrown out during volcanic eruptions.
Answer: (This is a repeat of Question 11).
Teacher's Tip: Review the three states of matter: Solid, Liquid, and Gas.
Exam Tip: Mention "Volcanic Bombs" as an example of large solid materials.

Describe any three advantages of volcanoes.
Answer: 1. Many minerals from the interior of the Earth come on to the surface.
2. Fertile soils like Black soil are made by breaking up of lava.
3. Electricity is generated from gases emitted out during volcanic eruptions.
Volcanoes aren't all bad! They bring up valuable metals like gold, create the best soil for growing cotton, and even provide clean energy from underground heat.
Teacher's Tip: Remember "M-S-E": Minerals, Soil, and Electricity.
Exam Tip: "Geothermal energy" is the scientific term for generating electricity from volcanic heat.

Question 15: Why are Earthquakes related to volcanoes ?
Answer: There is a close relationship between an Earthquake and a volcano Earthquakes and volcanoes occur in same belts i.e. mid-world belt and Circum Pacific belt. Their distribution shows a similar pattern. Volcanic eruptions lead to Earthquakes. Volcanic eruptions are the local cause of Earthquakes.
Where you find one, you usually find the other! Volcanoes cause earthquakes because the explosion and the moving magma shake the ground nearby like a giant truck driving past.
Teacher's Tip: Volcanoes and Earthquakes are like "partner in crime" - they are almost always found together.
Exam Tip: Mention that both occur in the same "belts" (like the Ring of Fire).

Question 16: What is a geyser ? Give two of its main characteristics. Name a well known geyser.
Answer: Geyser : Geysers are fountains of super heated steam and hot water that is usually emitted with an explosion trigged off by gases escaping from below
Main Characteristics of Geysers
1. Water in a geyser gets heated up beyond its boiling point.
2. They may spout to a height of over 150 feet.
A well known geyser is ‘Old Faithful’ in Yellow Stone National Park of Wyoming. It erupts regularly every hour and attracts a large number of tourists.
A geyser is like a giant natural teakettle that "whistles" by shooting hot water high into the air. They are very rare and only happen in places where there is lots of heat close to the surface.
Teacher's Tip: Think of "Old Faithful" as the world's most famous natural water fountain.
Exam Tip: The height "150 feet" and the example "Old Faithful" are key facts for this answer.

Question 17: State two ways in which lava may come out of the earth’s crust giving an example of each type of these volcanic activities.
Answer: Two main types of volcanic eruptions are :
• Explosive and
• Quiet or Hawaiian.
1. The Explosive eruption are the most violent and destructive Explosion of pent up gases mainly steam cause enormous quantities of magma to be thrown into the air to form great clouds. Example Krakatoa volcano in Sunda Strait in Indonesia erupt in 1883.
2. The Quiet eruption cause and other gases to escape. There is no violent explosion. Lava flows the creaters and flows down the sides of the cone. Example : Hawaiian volcanoes and Maupa Loa.
Volcanoes can either "explode" like a bomb (Explosive) or "leak" like a spilled bottle of water (Quiet). The type depends on how much gas is trapped inside the magma.
Teacher's Tip: Explosive is like a firework, and Quiet is like a candle melting.
Exam Tip: Use "Krakatoa" as the example for explosive and "Mauna Loa" for quiet eruptions.

Question 18: (a) What do you understand by ‘Vulcanism’ ? (b) What are ‘Volcanoes’ ? (c) How are volcanoes formed ? (d) Differentiate between active dormant and extinct volcanoes. (e) What is ‘magma’? (f) What do you understand by ‘Crater of the Volcano’ ?
Answer: (a) The interior part of the earth is extremely hot temperature upto 2000°C. in which every matter converts into molten form. This molten material ‘magma’ always tries to burst out whereever it finds any crack or hole in the crust. The process of erupting out of magma is known as ‘vulcanism’.
(b) ‘Volcanoes’ are the outlets of magma through a vent or cracks in the form of a conical volcanic hill or through various holes known as fissure eruption.
(c) Volcanoes are formed by the eruption of magma from the interior and deposited on the land surface and after cooling down take the shape of volcanoes.
(d) Active volcanoes go on erupting magma continuously e.g. stromboli (North of Sicily). Dormant volcanoes erupt in accidental intervals e.g. Mt. Vesuvius in Italy. Extinct volcanoes stop eruption for ever. e.g. Mt. Fujiyama in Japan.
(e) ‘Magma’ is the one word of several matters erupting out of a volcano e.g. lava, steam, cinderellas, stones, cinder, smoke etc.
(f) Crater of a volcano is the mouth of volcano in its vertex in the form of a circular hole.
This multi-part answer covers the A-Z of volcanoes. Vulcanism is the whole process, a volcano is the mountain itself, and the crater is the hole at the very top where the action happens.
Teacher's Tip: Vulcanism is the "Story" and the Volcano is the "Character."
Exam Tip: For the definition of "magma," include that it contains gases and steam as well as liquid rock.

Question 19: (a) Describe the distribution of volcanoes in the world. (b) What are the influences of volcanic eruptions on man ?
Answer: (a) Volcanoes are found along the weak zones of the earth’s crust where due to continuous tussle by tectonic forces maximum active volcanoes have created. These are :
1. Cirum-Pacific Belt- It is also known as ‘ring of fire due to consisting 75% active volcanoes of the world.
2. Mid-World Mountain Belt or Mid Continental Belt- It extends along the fold mountain zone of Alpine-Himalayan Region. Although this belt is noted for drastic earthquake but these are some of the very destructive volcanoes e.g. Stromboli Vesuvius Mt. Etna Mt. Pelee (West Indies). Out of these belts there are also various volcanoes scattered here and there.
(b) The effects of volcanoes on human life are both positive and negative :
Destructive influences : The deposition of lava makes the area very porous which creates water problem. The major flow of hot lava of Etna destroyed the whole area and property in Sicily. Mt. Vesuvius destroyed the city of Pompeii seven times since 79 AD. and the city of Herculaneum.
Constructive Influences : Volcanoes have provided some fertile lands e.g. Java and Deccan plateau and areas of South Brazil. Various precious minerals come out on the upper part of the earth’s crust through eruption e.g. Diamonds of Kimberley and gold of Johannesburg in South Africa nickel deposits of Sudbury in Canada.
Volcanoes are like nature's "double-edged sword." They can destroy entire cities like Pompeii in an instant, but they also give us the fertile ground needed to grow food and the deep-earth diamonds we wear in jewelry.
Teacher's Tip: Remember: Destructive = Death and Damage; Constructive = Crops and Crystals.
Exam Tip: Mention the "Diamonds of Kimberley" as a specific example of constructive influence.

Question 20: (a) What is an ‘earthquake’ ? (b) Give two major causes of earthquakes. (c) Describe the world’s distribution of earthquakes. (d) Mention some of the main effects of earthquakes. (e) Name the major earthquakes of India from 1991 to 1997.
Answer: (a) An earthquake is tremor or convulsion of the earth’s crust due to sudden movement of the crust.
(b) Two major causes of earthquakes are faulting associated with tectonic forces and the movements due to volcanic eruptions.
(c) The earthquakes are distributed along two major belts namely Circum Pacific earthquake belt (Ring of fire) and the Mid-World mountain earthquake belt along the great fold mountain zone.
(d) The destructive effects of earthquakes are very dangerous e.g. disruption of the rocks bed land slides changing the river courses floods tides collapsing of buildings destruction of transport lines and fires in electric wiring etc.
The constructive effects are the creation of additional coastal plains inlets bays for good harbours creation of fissure- openings to form sulphur or hot springs etc.
(e) Major earthquakes of India from 1919 to 1997.
• Latur 1991
• Uttarkashi 1993
Earthquakes are the planet's way of releasing stress. While they cause terrible damage like landslides and broken power lines, they can also "build" new land or create beautiful natural hot springs.
Teacher's Tip: An earthquake is just the Earth "readjusting" its heavy puzzle pieces (plates).
Exam Tip: Name "Latur" and "Uttarkashi" to correctly answer the question about Indian earthquakes.

Question 21: What are the following (a) Fissure type of volcanoes (b) Spine or plug (c) Caldera (d) Mud volcanoes (e) Epicentre (f) ‘Ring of Fire’ (g) Cinder Cone
Answer: (a) Some times the volcanic eruption takes place through several small holes which is known as fissure type volcanoes.
(b) The volcanic cone made by the quick solidification of viscous lava and having steep slopes is known as spine or plug.
(c) Caldera is the spacious crater of a volcano created by tremendous eruption. Crater lake in Oregon U.S.A occupies a caldera about 9 kilometre in diameter.
(d) Mud Volcanoes - A volcanic cone made of the mud due to the eruption of muddy water is called a mud volcano.
(e) Epicentre - It is the place of surface position immediately above the origin or focus of an earthquake.
(f) ‘Ring of Fire’ - It is the belt around the pacific ocean where due to the weak crust 75% of active volcanoes exist forming a huge ‘ring of fire’ phenomenon.
(g) Cinder Cone - The volcanic cone built of small pieces and fragments of solidified lava and ash is called ‘Cinder Cone’.
These are special scientific terms for volcanic shapes and earthquake spots. For example, a "Cinder Cone" is built like a pile of rubble, while a "Mud Volcano" looks like a mountain of chocolate-colored sludge!
Teacher's Tip: Think of a "Spine" as being a sharp, upright rock "needle."
Exam Tip: Remember that the "Epicentre" is the spot on the *ground*, while the "Focus" is the spot *underground*.

Question 22: (a) Distinguish between the following pairs of terms associated with vulcanicity 1. Lava and Magma 2. Acidic Lava and Basic Lava 3. Cinder Cone and Composite Cone 4. Fissure-type Volcanoes and Central-types Volcanoes 5. Crater and Caldera 6. Laccolith and Lapolith 7. Geysers and Hot Springs (b) Distinguish between the following pairs of terms associated with crustal movement of the earth 1. Graben and Horst 2. Tilted Block mountains and Lifted Block mountains
Answer: (a) (i) Lava and Magma : Lava is the black liquid part of the volcanic eruption. Magma includes all the material coming out of a volcano e.g. lava, stones, cinders, ash, smoke, steam etc.
(ii) Acidic Lava and Basic Lava : Acidic Lava is rich in silica and poor in iron and magnesium. Basic Lava is poor in silica and rich in iron and magnesium.
(iii) Cinder Cone and Composite Cone : Cinder Cone is made of small pieces and fragments of solidified lava and ash. Composite Cone is made of layers of cinders and ash, alternating with layers of lava.
(iv) Fissure type Volcanoes and Central type Volcanoes : If the vent is of such type that eruption comes out through various holes in a line of long crack, it is called fissure type volcanoes. If the vent is single and the magma erupting out takes the shape of a significant conical hill, it is known as central type volcanoes.
(v) Crater and Caldera : Crater is the mouth of a volcano at the top of the vent with normal outlet. Caldera is very large mouth of a volcano which is quite spacious due to big amount and thrust of the eruption.
(vi) Laccolith and Lapolith : Laccolith is a large sill of acid lava with a domelike shape. Lapolith is a saucer-like shaped feature deposited in shallow basins with the solidificaion of magma.
(vii) Geysers and Hot Springs : In a geyser, hot water and and steam are thrown out at intervals in the form of a fountain. In a hotspring the heated water flows out continuously without any eruptive activity.
(b) (i) Graben and Horst : Graben is another name for rift valley, which is trough like submerged park between two horsts (Block mountains). Horst is the elevated highland on the both sides of a rift valley, generally flat on the top. Another name for horst is the Block mountain.
(ii) Tilted Block mountain and Lifted Block mountain : A tilted block mountain has one steep slope and one gentle slope on another side. A lifted block mountain is bounded by steep slopes on both sides.
This comprehensive list helps you understand the "this vs that" of geology. For example, geysers are like fountains that turn on and off, while hot springs are like a tap that stays on all the time.
Teacher's Tip: Acid lava is like thick glue (slow and steep), and Basic lava is like water (fast and flat).
Exam Tip: Creating a T-chart is the best way to present these distinctions in an exam.

Question 23: Give a brief account of ‘Plate Tectonics’.
Answer: In the beginning all the continents were combined together known as ‘Pangasa’ which later on splitted away and separated. But still all continental and oceanic plates are sliding upon each other and result in various earthquakes and volcanoes. The continental drifting theory was discovered by German scientist Alfred Wagner in 1912 which supported this plate tectonics to prove the movement of the continental and oceanic plates working for changing the landforms of the crust.
Earth's outer shell is not one solid piece, but a giant jigsaw puzzle made of floating pieces called "plates." These plates are constantly moving, which is why continents used to be stuck together in one big lump called Pangaea and are still slowly shifting today.
Teacher's Tip: Think of Plate Tectonics as Earth's giant game of "bumper cars" using continents!
Exam Tip: Remember the name "Alfred Wagner" and the year "1912" as the origins of this theory.

Question 24: Give reasons for the following 1. The Belts of volcanic activity and earthquakes are roughly the same. 2. Basic lava cones are broader than Acid lava cones. 3. The Circum-Pacific Belt of volcanoes is called ‘The Ring of Fire’.
Answer: 1. The volcanoes and earthquakes are associated with each other as every volcanic activity takes place by shaking and breaking the weak crust which naturally creates tremors and earthquakes within the earth’s crust.
2. Basic lava cones are broader than the Acid lava cones because basic lava is very fluid and flows easily for a great distance before it solidifies where as acid lava is highly viscous and flows only for a short distance.
3. The circum-pacific belt is truly known as “The Belt of Fire” or “The Ring of Fire” as 75% active volcanoes erupting fire are located in this belt.
The reason for these geographical facts is all about how the Earth's internal heat moves and how the magma flows. Runny lava makes wide mountains, and active volcanoes create constant earthquakes by cracking the ground.
Teacher's Tip: Runny lava = Wide hills. Sticky lava = Tall peaks.
Exam Tip: Mention that 75% of volcanoes are in the Ring of Fire to explain its name effectively.

Question 25: Match the items given in Column A with the correct ones in Column B.
Column A - Column B
(a) A Rift Valley lake - (a) Tanganiyaka
(b) A horst - (b) Black forest plateau.
(c) A basic lava sheet - (c) Deccan Trap region of India
(d) Composite cones - (d) Fujiyama
(e) An active volcano - (e) Stromboli
(f) A Batholith - (f) Upland of Britany in France
(g) A Phaccolith - (g) Corndon Hill
(h) A young Fold mountain - (h) The Alps
Answer:
(a) A Rift Valley lake - (a) Tanganiyaka
(b) A horst - (b) Black forest plateau.
(c) A basic lava sheet - (c) Deccan Trap region of India
(d) Composite cones - (d) Fujiyama
(e) An active volcano - (e) Stromboli
(f) A Batholith - (f) Upland of Britany in France
(g) A Phaccolith - (g) Corndon Hill
(h) A young Fold mountain - (h) The Alps
This matching exercise connects real-world landmarks to their geological origins. For example, the Alps are "young" mountains, and Lake Tanganyika is a sunken "rift" filled with water.
Teacher's Tip: Use "Fujiyama" (Mt. Fuji) to remember the cone shape - it is one of the most perfectly shaped volcanoes in the world!
Exam Tip: Be sure you can name at least one example for every landform type mentioned in the list.

Question 26: Give one word for the following : 1. A narrow block elevated between two normal faults. 2. The funnel shaped hollow at the top of a volcanic cone. 3. The lava which is poor in silica and rich in iron and magnesium. 4. A volcano which has the possibility of erupting in future. 5. A large sill of acid lava which has solidified gradually giving a dome - like shape. 6. A volcano where magma reaches the surface through a vent or a pipe. 7. A volcano whose eruption buried and destroyed two Roman towns. 8. An instrument used for recording all the earth tremors and earthquakes. 9. The surface position immediately above the origin of an earthquake. 10.The region where there are highest number of geysers and hot springs.
Answer: 1. Horst
2. Crater
3. Basic-Lava
4. Dormant Volcano
5. Acid-Lava Dome
6. Central type volcano
7. Vesuvius
8. Seismograph
9. Epicentre
10.Yellow stone park (U.S.A.)
This is a quick vocabulary test. Knowing that a "Seismograph" is the machine that draws earthquake lines or that "Vesuvius" destroyed Pompeii is essential for Class 6 geography.
Teacher's Tip: Think of the Seismograph as a "shaking pen" that writes the story of the Earth's movement.
Exam Tip: One-word answers must be spelled perfectly to ensure you don't lose simple marks.

Question 27: (a) Which type of lavas weather into more fertile soil. Name also one useful feature of volcanicity other than soil fertility. (b) Which four of the following words are connected with volcanic activity : Karst, crater, drumlin, stalactite, gully, potholesl, ash, basalt, swallow, holes, dyke, domes, bluffs.
Answer: (a) Basic - type lava sheet weather into fertile soil e.g.Deccan trap soil. Other useful feature of volcanicity is that the precious minerals come out with the magma near the land surface e.g. diamond and gold etc. (b) Crater, ash, dyke, domes.
Volcanoes are like "Earth's farmers" and "Earth's miners." They turn rocky lava into black soil that is great for crops, and they bring deep gold and diamonds close enough for humans to find.
Teacher's Tip: The Deccan Trap in India is famous for growing cotton because of its fertile volcanic soil.
Exam Tip: Be able to pick out volcanic words like "crater" from a mixed list of terms.

Question 28: What are tectonic movements ? How are these classified?
Answer: Tectonic movements are changes through earth’s natural activities which are known as ‘diastrophism’. These movements are of two types e.g. vertical movement and horizontal movement.
Tectonic movements are simply the giant "shuffling" of the Earth's crust. They can either push land straight up and down (vertical) or squeeze it from the sides to make wrinkles (horizontal).
Teacher's Tip: Horizontal makes Mountains; Vertical makes Continents and Plateaus.
Exam Tip: Use the scientific word "diastrophism" to describe these slow, powerful movements.

Question 29: Give reasons for the following : 1. Earth movements have modified the Earth’s surface. 2. Internal processes are different from external processes. 3. Folding and faulting frequently go together. 4. Earth as a whole does not expand.
Answer: 1. Earth movements like Continental Drift theory changed the whole face of the earth into distinct continents and oceans of today with highest mountains plateaus plains drainage system and so on.
2. Internal processes are associated with tectonic forces resulting in drastic changes e.g. earthquakes volcanoes etc. External processes are carried on by natural agents of change e.g. water wind and ice which produce gradual changes.
3. Folding and Faulting frequently go together because the stress on folding exceeds more than enough then folds break through fault line to two pieces slipping one upon another which is called faulting.
4. Inspite of various changes occurring within the earth it does not expand as it is affected by the centripital force of gravity working towards the centre of the earth.
The Earth is like a living thing that is always changing. While inner forces (volcanoes) build things up quickly, outer forces (rain) wear them down slowly, and gravity keeps the whole planet from getting too big or falling apart.
Teacher's Tip: Internal = Builder; External = Sculptor.
Exam Tip: Explain that "Centripetal force" or gravity is what keeps the Earth's size constant.

Question 30: How the theory of plate tectonics has explained the formation of mountains like Himalaya or Alps and of the volcanic islands.
Answer: The formation of the highest mountains of Himalayas and Alps have been created by the bucking up of the geo synclines of tethys sea between Angaraland and Gondwanaland which pushed towards each other and forced the geosynclines to be lifted up forming the mountains. The Mid-Atlantic Ridge is the proof of the edge raised at the joint of continental plates which gives birth to several volcanic islands.
Mountains like the Himalayas were actually once the bottom of a sea! Giant pieces of land crashed into each other like cars in slow motion, squashing the sea floor and pushing it up into the highest peaks on Earth.
Teacher's Tip: Think of the Himalayas as a giant "crumple zone" between two crashing continents.
Exam Tip: Mention the "Tethys Sea" when explaining how the Himalayas were formed.

Question 31: (a) Describe the distribution of volcanoes in the world. (b) What are the influences of volcanoes eruption on man? Mention adverse and beneficial effects of volcanoes.
Answer: (a) Obviously volcanoes will be found in those regions where the crust of the earth is weak because lava can easily be discharged from such places. These are found in areas of Fold mountains. There are three main belts of volcanoes :
1. Circum-Pacific Belt : This belt runs round the Pacific Ocean in Asia and the America. It starts from Cape Horn goes along the Andes and the Rockies to Alaska. Some of the well known Volcanoes are Karakatoa Mayon Fujiyama Chimborezo and Cotopaxi.
2. Mid World Mountain Belts : This belt starts from the West Indies and reaches the Himalayas. Mt. Vesuvius Mt Stromboli Etna and Mt. Pelee are the important Volcanoes of this belt.
3. African Belts : This belt follows the Great African Rift Valley. Important Volcanoes are Kilimanjaro Kenya Canary Islands St. Helena.
(b) Adverse effects of volcanoes : 1. Most of the recently formed volcanic areas are barren and forbidding to man. 2. The sudden flow of basic lava from an eruptive volcano may cause the total destruction of human life property and crops. 3. The Karakatoa volcanic eruption caused such high sea waves that islands were destroyed. 4. Volcanoes eruption of Vesuvius buried Pompeii.
Beneficial effects of Volcanoes : 1. The soil made up of lava is very fertile. 2. Lakes are formed when the craters are filled up with waters. 3. Several minerals come up near the surface of the earth. 4. Lava flows have preserved many fossils.
Volcanoes are nature's way of recycling the planet. While they are terrifying when they explode and bury cities, they are also the reason we have beautiful mountain lakes and the fertile ground where we grow our food.
Teacher's Tip: Volcanoes are like fire: they can burn your house down, but they also keep you warm and cook your food!
Exam Tip: Providing a list of specific volcanoes like "Mt. Kilimanjaro" or "Mt. Vesuvius" will earn you high marks.

Question 32: What are the following :
(a) Fissure type of volcanoes
(b) Spine or plug
(c) Caldera
(d) Mud volcanoes
(e) Epicentre
(f) ‘Ring of Fire’
(g) Cinder Cone
Answer: (a) Fissure type of volcanoes : If the vent is in the form of a long crack then it is knows as a Fissure Type Volcano. In this type volcanic activity occurs quietly the lava upwells silently and spreads over a large area.
(b) Spine or plug : Acid lava dome is formed when viscous lava solidifies quickly and gives rise to steep sloping cones. This is known as a spine or plug.
(c) Caldera : In some volcanoes the summit of the volcano blows up during a violent explosion resulting in the formation of a large depression called a Caldera. In the state of Oregon there is a caldera about 9 km in diameter.
(d) Mud volcanoes : If water which erupts in a volcano is muddy then a conical mound of mud is formed within a creater at the top. This is known as a mud volcano.
(e) Epicentre : The point on the earth’s surface directly above the ‘focus’ of earthquake is called epicentre.
(f) Ring of Fire ; The Circum-Pacific Belt of volcanoes encircles the Pacific Ocean. It is called the ‘Ring of Fire’ because there are a large number of active volcanoes in it.
(g) Cinder cone : When the lava is ejected from a central vent its pieces and fragments solidify round the vent to form a cone. This is known as a Cinder Cone.
(See Question 21 for extension and tips).
Teacher's Tip: A "Plug" is like a cork stuck in the volcano's neck!
Exam Tip: Be able to match the name (e.g. Mud Volcano) with its description (e.g. conical mound of mud).

Question 33: Distinguish between the following pairs of terms associated with vulcanicity
1. Magma and Lava 2. Acidic Lava and Basic lava 3. Cinder Cone and Composite Cone 4. Fissure-type Volcanoes and Central Type Volcanoes 5. Crater and Caldera 6. Laccolith and Lapolith 7. Geysers and Hot springs 8. Active Volcano and Dormant Volcano 9. Folding and Faulting 10.Volcanic Cone and Volcanic Plateau 11.Seismic Focus and Epicentre 12.Dykes and Sills (b) Distinguish between the following pair of terms associated with crustal movement of the Earth 1. Graben and Horst 2. Tilted Block Mountains and Listed Block Mountains
Answer: (i) Magma and Lava : Magma is hot sticky molten material containing solutions of water and gases. Lava is solidified magma where gases and water disappear after evaporation.
(ii) Acidic Lava and Basic lava : Acidic Lava is highly viscous, light coloured like granite, and has a high percentage of silica. Basic Lava is highly fine and thin, dark coloured like Basalt, and poor in silica.
(iii) Cinder Cone and Composite Cone : Cinder cones have steep slopes because they consist of large particles. Composite cones start as cinder cones and grow into large volcanic hills with alternating layers of lava and ash.
(iv) Fissure type of volcanoes and Central-type Volcanoes : Fissure volcanoes erupt quietly from a long crack and spread lava over a large area. Central type volcanoes erupt from a single vent and form a significant conical hill.
(v) Crater and Caldera : Crater forms the summit mouth. Caldera is the enlarged mouth or sunken crater at the centre of a volcano.
(vi) Laccoliths and Lapoliths : Laccoliths are large lens-shaped dome intrusions. Lapoliths are saucer-shaped intrusive layers.
(vii) Hot Springs and Geysers : Hot Spring is a stream of hot water flowing unobstructed and continuously. Geyser is a hot spring which throws a jet of hot water and steam into the air at regular intervals.
These distinctions help you "classify" everything volcanic. Whether it's the shape of a rock (saucer vs lens) or the way a spring behaves (continuous vs fountain), every word has a specific meaning.
Teacher's Tip: Use the shape to remember: Laccolith = Lens, Lapolith = Saucer.
Exam Tip: In your distinction for "Lava vs Magma," include that "Lava" cools down when it hits the "atmosphere."

Question 34: Give reasons for the following : 1. The Belts of volcanic activity and earthquakes are roughly the same. 2. Basic lava cones are broader than the Acid lava cones. 3. The Circum-Pacific Belt of volcanoes is called ‘The Ring of Fire’.
Answer: 1. The belts of volcanic activity and earthquakes are roughly the same because the movement of magma beneath the Earth is the main cause of earthquakes and volcanoes.
2. Basic lava cones are broader than the Acid lava cones because basic lava is very fluid and flows easily for a great distance before it solidifies where as acid lava is highly viscous and flows only for a short distance.
3. The Circum-Pacific belt of volcanoes is called “The Ring of Fire” because there are large number of fire volcanoes in it.
(See Question 24 for extension and tips).
Teacher's Tip: Remember: Basic = Broad (because it flows like water).
Exam Tip: Be sure to link "viscosity" to the shape of the volcano cone.

Question 35: (a) Name one useful feature of volcanicity other than soil fertility. (b) Out of the following words write down the four that are connected with volcanic activity. Karst, crater, drumlin, stalacities, gully, pot holes, ash, basalt, swallow holes, dyke, domes, bluffs.
Answer: (a) The molten rocks of vulcanicity is of considerable environmental significance since it is the direct or indirect cause of several classes of landforms. Basic lava weather into more fertile soils. (b) Crater, ash, basalt, dyke are connected with volcanic activity.
Volcanoes are the "engineers" of the planet, building everything from islands to mountains. Beyond making good soil, they help us understand the deep history of our Earth's inner layers.
Teacher's Tip: A dyke is like an underground stone wall built by a volcano!
Exam Tip: Make sure you can tell the difference between "volcanic" terms and "river" or "karst" terms.

Question 36: Give reasons for the following : 1. Earth’s movements have modified the Earth’s surface. 2. Earth as a whole does not expand.
Answer: 1. The surface of the earth is undergoing constant change. Sudden changes like volcanic eruptions and earthquakes, and slow changes like Continental Drift have modified the surface. Sediments originally deposited horizontally are found tilted and bent, and lands that were once at sea-level are now high above the water.
2. About six important Convection Current Cells below the Lithosphere add new crust along Mid-Oceanic ridges (spreading). At the same time, the crust at the other edges of the plates in oceanic trenches gets destroyed. Consequently a balance exists and the Earth as a whole does not expand.
The Earth is constantly "making" new skin and "eating" old skin at the same time. This keeps the planet the same size even though the seafloor is always moving and growing.
Teacher's Tip: Think of the Earth like a conveyor belt: new land comes up in the middle of the ocean, and old land is recycled back into the mantle at the edges.
Exam Tip: Use the term "constructive plate movement" for seafloor spreading and "destructive" for when crust is recycled.

Question 37: Answer the following : 1. Some volcanoes erupt explosively 2. Some volcanoes develop parasitic cones. 3. Hot springs are common in volcanic regions. 4. Earthquakes are common in the belt of young fold mountains. 5. Plate margins are zones of great volcanic activity. 6. Volcanic eruption is one of the main causes of earthquakes. 7. The vent of a volcano when blocked results in explosive eruption.
Answer: 1. Some Volcanoes erupt explosively because the vent of a volcano may be blocked by some sticky material or rock which causes the explosion.
2. Some volcanoes develop parasitic cones because the main vent grows too high and develops a parasite or a branch cone.
3. Hot springs are common in volcanic regions because undergound water gets heated by contact with hot magma.
4. Earthquakes are common in the belt of young fold mountains because these mountains are in a state of constant flux.
5. Plate margins are zones of great volcanic activity because collisions of plate margins produce the magma and allow it to escape through a vent, a fissure or a crack.
6. Volcanic eruption is one of the main causes of earthquakes bacause volcanic earthquakes are caused by gas explosions. Such earthquakes occur either simultaneously with eruption or more commonly in the period preceding an eruption.
7. It causes the pressure to build up which results in violent explosion.
This final summary explains the "why" behind the most exciting volcanic events. Whether it's a blocked vent causing a massive boom or magma creating a second smaller volcano on the side of a big one, these are all results of heat and pressure.
Teacher's Tip: A parasitic cone is like a "branch" on a tree - it's a smaller part growing off the main one.
Exam Tip: Use the term "viscous lava" to describe the sticky material that blocks a volcano's vent.