The Changing Earth Notes Class 10 Geography Chapter 6 Kerala Syllabus Questions and Answers

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SSLC Geography Chapter 6 Notes Pdf English Medium The Changing Earth

SCERT Class 10 Social Science Geography Chapter 6 The Changing Earth Notes Question Answer Kerala Syllabus

Class 10 Geography Chapter 6 Notes Kerala Syllabus The Changing Earth

Question 1.
Identify the geographical phenomenon to which each picture relates, and write them in the appropriate boxes.

Answer:
a) Earthquake
b) Volcanic Eruption
c) Plate Tectonics / Movement of Lithospheric Plates

Question 2.
List out the differences between epeirogenic movements and orogenic movements.
Answer:

Epeirogenic movements	Orogenic movements
• The processes that cause the upliftment of a large portion of the Earth’s crust are called epeirogenic movements. • These movements cause only minimal deformation on the Earth’s surface, whereas in orogenic movements, the Earth’s surface is severely deformed.	• The processes that cause the formation of mountains are called orogenic movements. Fold mountains are formed through the folding of crustal portions.

Question 3.
With the help of Information Technology, identify the major fold mountains of the world and mark them on an outline map of the world. Include the map in My Own Atlas.
Answer:

Question 4.
Observe the diagram given below and identify the structure of a volcano. Prepare a note describing its structure and present it in the classroom. Make a model of a volcano.

Answer:

1. Magma Chamber – The large underground reservoir where molten rock (magma) is stored.
2. Vent – The passage through which magma rises to the surface.
3. Crater – The bowl-shaped opening at the top of the volcano.
4. Lava Flow – The molten rock that flows out during an eruption.
5. Ash Cloud & Layer of Ash – Fine particles of ash and gases released into the atmosphere.
6. Sill – A horizontal sheet of cooled lava inside the Earth’s crust.
7. Laccolith – Dome-shaped intrusions formed when magma pushes up rock layers.

Hints to make a model of a volcano:
Materials Needed:

1. A small plastic bottle or cup (to act as the vent).
2. Clay, or soil (to build the cone of the volcano).
3. A large tray or cardboard sheet (as the base).
4. Paint or colours (to decorate the volcano with lava streaks, rocks, and greenery).
5. For eruption: baking soda, vinegar, red/orange food colour, and dish soap.

Steps:

1. Fix the plastic bottle in the middle of the tray.
2. Cover it with clay or mud, shaping it like a cone (leaving the bottle’s mouth open).
3. Paint the outside to look like a real volcano – grey or brown for rocks, green at the base, and red/orange streaks for lava.
4. For eruption: put 2 – 3 spoons of baking soda inside the bottle. Add a few drops of dish soap and red/orange food colour.
5. Put vinegar slowly into the bottle. It will foam up and flow down like real lava.

Question 5.
Collect pictures of different types of volcanoes and create a digital album. Write the name of each
volcano, and the country it is situated in.
Answer:

Question 6.
a) With the help of Information Technology, download a world map showing the plate margins. Mark these plate margins on the world map that shows the distribution of volcanoes.
Answer:

b) Repeat the same activity on an outline map of the world and include it in My Own Atlas.
Answer:

Question 7.
The major volcanic zones are mainly located along major plate margins. Why is this so? Hold a discussion in the classroom.
Answer:
The major volcanic zones are mainly located along the major plate margins because these are areas where the Earth’s crust is most active. At convergent boundaries, one plate moves under another, causing the mantle to melt and form magma, which can rise to the surface as volcanoes. At divergent boundaries, plates move apart, creating gaps through which magma reaches the surface. Even along transform boundaries, cracks in the crust can allow magma to emerge. Therefore, most volcanoes are found along plate margins due to the movement and interaction of tectonic plates.

Question 8.
Find out and write down what other impacts volcanic eruptions have on human life.
Answer:

1. Volcanic ash and gases can cause respiratory problems, eye irritation, and skin issues.
2. Agricultural Damage
3. Air travel may be disrupted due to ash clouds
4. Affect the climate by lowering temperatures and altering weather patterns
5. Infrastructure Damage

Question 9.
With the help of Information Technology, collect news related to volcanic eruptions in the recent years, prepare a collage, and display it in the classroom.
Answer:

Question 10.
Which is the only active volcano in India?
Answer:
Barren Island Volcano, located in the Andaman and Nicobar Islands in the Bay of Bengal.

Question 11.
There is an extensive area in India where soil has been formed from the disintegration of lava rocks. Which is that region?
Answer:
The Deccan Trap region of the Deccan Plateau.

Question 12.
Why do lithospheric plates slide over the asthenosphere?
Answer:
Lithospheric plates slide over the asthenosphere because the heat from the Earth’s interior creates convection currents in the semi-molten asthenosphere, which move the plates.

Question 13.
The Himalayan regions are highly vulnerable or susceptible to earthquakes. Why?
Answer:
The Himalayan regions are highly vulnerable to earthquakes because they lie at the boundary of the Indian and Eurasian plates, where the plates constantly collide and create stress in the Earth’s crust.

Question 14.
The map given below shows the distribution of the major tectonic earthquake regions. Analyse the map and identify the major seismic regions of the world.

Answer:

• Circum-Pacific Belt (Ring of Fire )
• Mediterranean-Himalayan Belt (Alpine Belt)
• Mid-Atlantic Ridge Belt

Question 15.
On the earlier map prepared by you to show the distribution of volcanoes, mark the major seismic regions using a different colour.
Answer:

Question 16.
An earthquake occurred in Turkey and in adjoining areas on 6th February 2023. Given below are the headlines related to it. Examine the news headlines and list the possible disasters caused by earthquake.

• The earthquake that struck Turkey created havoc in the southeastern part of the country and killed thousands of people. • The earthquake, which measured 7.8 on the Richter scale, destroyed hundreds of buildings. • The transportation and communication systems were shattered, and water distribution failed. • The food supply was disrupted, and the shortage of medicines was severe. • Rescue operations made difficult by landslides and fires.

Answer:
• Large-scale loss of human lives.
• Collapse and destruction of hundreds of buildings.
• Damage to transportation and communication systems.
• Failure of water distribution.
• Disruption of food supply and severe shortage of medicines.
• Landslides and out break of fires, making rescue operations difficult.

Question 17.
Visit the official website of the National Disaster Management Authority and complete the following activities.
a) Analyse the map of India showing the major seismic zones and mark them on an outline map of India.
b) Examine the information given on the website and prepare a chart titled ‘How to Face an Earthquake’. Display it in the classroom.
Answer:
(Hints)
a) Step 1: Visit the official website of the NDMA ( https://ndma.nov.in )
Step 2: Select Earthquakes from Natural Hazards
Step 3: Analyse the Seismic Zone Map and mark it on an outline map of India

b)

How to Face an Earthquake
Before the disaster	During the disaster	After the disaster
• Keep an emergency kit (water, food, first-aid, flashlight) • Identify safe spots in your home or classroom (under tables, against interior walls)	• Stay away from windows, mirrors, and falling objects. • If outdoors, move to an open area away from buildings, trees, and power lines.	• Keep calm, switch on the radio/TV and obey any instructions you hear on it. • Be prepared to expect aftershocks.

Question 18.
Prepare a list of items to be included in an emergency kit and display it in the classroom.
Answer:

1. Drinking water
2. Non-perishable food (canned food, dry snacks, energy bars)
3. First-aid kit
4. Face masks
5. Flashlight with extra batteries

Question 19.
Visit the Kids Corner on the Kerala Disaster Management Authority’s website and play the game titled ‘Know the Earthquake’ with your friends. Share the information you gain from the game in the classroom.
Answer:
(Hints)

1. Step 1: Go to the Kerala Disaster Management Authority website (https://sdma.kerala.gov.in)
2. Step 2: Click on “Kids Comer.”
3. Step 3: Play the game “Know the Earthquake” with your friends.
4. Step 4: Note down important points about earthquakes and safety.
5. Step 5: Share what you learned in the classroom.

Question 20.
Visit the official websites of the National Disaster Management Authority (NDMA) and the Kerala State Disaster Management Authority (KSDMA). Collect additional information about tsunami disaster management measures, prepare a poster, and display it in your classroom.
Answer:
(Hints)

• Title: “Tsunami Safety: Be Prepared, Stay Safe”
• Visuals: Use clear images depicting tsunami evacuation routes, warning signs, and safety measures.
• Content Layout: Organize information into sections with headings like “What is a Tsunami?”, “Early Warning Signs”, “Safety Tips”, and “Role of Authorities”.
• Color Scheme: Use blue tones to represent water and white for clarity.
• Language: Ensure the language is simple and accessible for all students.

Question 21.
Observe the diagram (Fig 6.1) and list the driving or causative forces of exogenic movements (Exogenic forces). (Refer Topic 1)

Answer:

• Slope formed on the Earth’s surface
• Gravity
• Pressure exerted.on an object by another object
• Molecular stress

Question 22.
Do human activities cause weathering? List the human activities that contribute to the weathering of rocks.
Answer:
Yes, human activities can accelerate the weathering.

1. Mining
2. Quarrying
3. Construction activities
4. Deforestation
5. Agricultural practices (Overuse of chemical fertilizers)

Question 23.
Visit the official website of the Kerala State Disaster Management Authority. Find out the major causes of debris flow/landslide in Kerala, and complete the list.
Answer:

1. Unscientific construction of houses, roads, etc., on steep slopes
2. Interruption of the natural flow of streams
3. Heavy Rainfall
4. Steep Slopes

Question 24.
Visit the official website of the Kerala State Disaster Management Authority and examine the landslide/
debris flow-prone area map. Find out whether your school and house are located in such an area.
Answer:
(Hint)
“Go to the KSDM A website (https://sdma.kerala.gov.in). check the landslide/debris flow-prone area map of Kerala, locate your district, then find the exact location of your school and house on the map to see if they fall in a high-, moderate, or low-risk zone.”

Question 25.
Prepare a note by collecting information about the measures adopted by the Government of Kerala to mitigate the impact of the recent Urulpottal (debris flow) incidents in the state.
Answer:
The Government of Kerala has adopted several measures to mitigate the impact of recent Urulpottal (debris flow) incidents. The Kerala State Disaster Management Authority (KSDMA) has prepared detailed hazard maps and run-out path analyses to identify high-risk areas. Infrastructure improvements, such as strengthening embankments, improving drainage systems, and constructing retaining walls, have been carried out to stabilize slopes. Strict regulations on construction activities and land use planning help prevent habitation in vulnerable zones. The government also focuses on community awareness through public campaigns and regular drills, ensuring people are prepared for emergencies. During incidents, control rooms and helplines provide assistance, while immediate relief in the form of food, shelter, and medical aid is provided to affected communities.

Std 10 Geography Chapter 6 Notes Kerala Syllabus – Extended Activities

Question 1.
Identify the human activities that contribute to the weathering of rocks by observing your surroundings, and list them.
Answer:
Yes, human activities can accelerate the weathering.

• Mining
• Quarrying
• Construction activities
• Deforestation
• Agricultural practices (Overuse of chemical fertilizers)

Question 2.
Conduct a seminar on ‘Tectonic movements and Earthquakes’.
Answer:
(Hints: Conduct a seminar by using the given steps)

1. Step 1: Start with an Introduction
2. Step 2: Explain the types of Tectonic Movements (Divergent boundary, Convergent boundary, Transform boundary)
3. Step 3: Explain Earthquakes and its Causes
4. Step 4: Effects of Earthquakes
5. Step 5: Safety Measures
6. Step 6: Use Visual Aids
7. Step 7: Conclusion

Question 3.
Conduct Mock drills in classrooms to raise awareness among students about disaster mitigation measures.
Answer:
(Hints)

1. Step 1: Plan the Drill
2. Step 2: Explain the Drill to Students
3. Step 3: Assign Roles (Teacher or staff to guide students and monitor safety)
4. Step 4: Conduct the Drill
   • Start with an alarm or signal.
   • Students follow the practiced safety procedures.
   • Teachers ensure everyone is safe and counts students at assembly points.
5. Step 5: Debrief and Discuss (Discuss what went well and what could be improved)
6. Step 6: Repeat Regularly
   • Conduct drills at different times to ensure all students are familiar with procedures.
   • Encourage students to practice disaster safety at home as well.

Question 4.
Visit the official website of the Kerala Disaster Management Authority to gather information about potential disasters and mitigation strategies, then prepare a poster and display it in the classroom.
Answer:
(Hints for Poster)

• Give a Proper Title
• List common disasters in your area (Landslides, Flood, etc)
• Mitigation Strategies (For each disaster, give simple ways to stay safe)
• Visual Elements (Use icons or drawings for each disaster)

Question 5.
Visit the official website of the Kerala Disaster Management Authority to download the map of Kerala showing Urulpottal-prone regions, and draw it on chart paper. Display it in the Social Science lab.
Answer:
(Hints)

1. Step 1: Visit the Website (https://sdma.kerala.gov.in)
2. Step 2: Search for Maps (Find the map showing Urulpottal-prone regions)
3. Step 3: Download the Map and draw it on Chart Paper

Question 6.
If your house or school is located in a disaster-prone region, hold discussions on disaster mitigation strategies, prepare notes and posters, and raise awareness among the people living in such areas.
Answer:
(Hints)

1. Step 1: Identify the Disaster-Prone Area
2. Step 2: Hold Discussions (Types of disasters that may occur, Past incidents and their impact, Possible safety measures)
3. Step 3: Prepare Notes
4. Step 4: Prepare Posters (Title, Visuals, Safety measures)
5. Step 5: Raise Awareness (Display posters in schools and public places)

Question 7.
With the help of your teacher, practise the precautionary methods that can help you escape from an Urulpottal.
Answer:
How To Face Urulpottal

At the time of the disaster	After the disaster
• Stay calm and do not panic • During Urulpottal, if you are inside your house, take shelter under a strong table or cot. • If you are outside, move quickly to safer and higher ground, away from slopes and loose soil.	• Allow ambulances and other rescue vehicles to pass without obstruction • Report immediately to t he authorities if you notice any fallen electric lines in LTrulpottai – affected regions. • Help people who are injured or trapped and provide first aid if possible.

KaWaCHam: Kerala Warnings, Crisis and Hazard Management System
It is a disaster warning system implemented in the state of Kerala, ensuring the use of modem technologies in disaster mitigation activities. All disaster-prone areas of Kerala are covered under this integrated warning system. Kerala is the first state in the country to implement a disaster warning system of this kind. The project aims to monitor the possibility of disasters in all areas. If any disaster is detected, the public is alerted through location-based SMS, social media updates, and by activating siren-strobe light units. Necessary precautionary measures are then taken at different levels.

Question 8.
Read the Post-Disaster Needs Assessment report prepared by the Government of Kerala in co-operation with UNDP, the World Bank, and the European Union following the 2018 flood, then draw conclusions.
Answer:
The Post-Disaster Needs Assessment (PDNA) report prepared by the Government of Kerala in collaboration with UNDP, the World Bank, and the European Union after the 2018 floods concluded that the disaster caused severe damage to housing, agriculture, infrastructure, and livelihoods, affecting millions of people across the state. The report highlighted the urgent need for rebuilding on the principles of resilience and sustainability, instead of merely restoring what was lost. It emphasized strengthening disaster preparedness, improving early warning systems, adopting flood-resilient construction practices, restoring ecosystems like wetlands and rivers, and ensuring community participation in recovery efforts. Overall, the PDNA stressed that Kerala should focus on “building back better” to reduce, future risks and protect both people and the environment.

The Changing Earth Class 10 Notes Pdf

• The movements that cause the ups and downs on a the surface of the Earth are called the Earth movements.
• Many geographical phenomena and natural disasters occur in connection with Earth movements.
• Endogenic and Exogenic are the two types of a Earth Movements.
• The continuous cyclic movement of magma in the mantle, driven by thermal variations, is called
  convection current.
• A hazard is generally referred to as a situation that poses a threat to life, health, property, services, socio-economic stability, or the environment.
• A disaster can be defined as a serious disruption in the functioning of a community or society that causes widespread material, economic, social, or a environmental losses, and exceeds the ability of the affected society to cope using its own resources.
• Slow movements (also called diastrophic a movements) and sudden movements are the # two types of Endogenic Movements.
• The endogenic movements that move, elevate, or build up portions of the Earth’s cmst are collectively known as diastrophic movements.
• The processes that cause the upiiftment of a large portion of the Earth’s crust are called epeirogenic movements.
• The processes that cause the formation of mountains are called orogenic movements.
• The uplifted block of the Earth’s crust formed due
  to faulting is called a horst (block mountain). The corresponding down-dropped block of the Earth’s crust is called a graben.
• Endogenic forces caused sudden movements like volcanic eruptions and earthquakes.
• Three types of waves are generated from the focus of an earthquake. Primary waves, secondary waves, and surface waves.
• The Exogenic forces are responsible for various processes that operate on the surface of the Earth, such as weathering, erosion, transportation, deposition, and mass wasting. These processes are collectively known as exogenic movements.
• Each exogenic process derives its energy from different external forces, which are called the driving forces of exogenic movements.
• The processes that bring about these chemical and mechanical changes in rocks are called weathering. • In addition to weathering and erosion, another type of earth movement that occurs on the surface of the Earth due to exogenic forces is mass wasting.
• ‘Urulpottal ’ is a type of mass wasting.
• Studies using toals like remote sensing and Geographic Information Systems (GIS) can help us identify areas that have a higher possibility of ‘Urulpottal’ (debris flow or landslide).
• The sudden movement of rock debris and soil mixed with water down a steep slope under the direct influence of gravity is called a debris flow.

INTRODUCTION

Through this chapter we have been discussing various Earth movements and the associated natural disasters, along with their mitigation measures. Natural calamities often turn into disasters due to the conflict between human activities and nature. Nature is the abode we inhabit. The human activities carried out in it, and the consequent changes in nature, are together referred to as development. Both human activities and development are not only complementary but also essential. Each disaster reminds us that unlimited development is impossible in a world with its limit. This is where the role of sustainable development becomes important. It is necessary to make democratic decisions and implement them to safeguard both people and the environment without causing environmental destruction. Resource utilisation should focus on ensuring access to sufficient resources through cooperation, rather than acquiring as much resources as possible through competition. It is necessary to meet the needs of the present generation without compromising on the ability of nature to meet the needs of future generations. We can protect nature by safeguarding ourselves.

Earth Movements

• The movements that cause the ups and downs on the surface of the Earth are called the Earth movements.
• Endogenic and Exogenic are the two types of Earth Movements.
• The continuous cyclic movement of magma in the mantle, driven by thermal variations, is called
  convection current.
• A hazard is generally referred to as a situation that poses a threat to life, health, property, services, socio-economic stability, or the environment.
• A disaster can be defined as a serious disruption in the functioning of a community or society that causes widespread material, economic, social, or environmental losses, and exceeds the ability of the affected society to cope using its own resources.
• In the context of disasters, vulnerability can be defined as the extent to which a community,
  structure, service, or geographic area is likely to be damaged or disrupted by the impact of a particular hazard.
• Capacity refers to the resources, means, and strengths within a community that enable it to cope with, withstand, prepare for, prevent, mitigate, or quickly recover from a disaster.
• Risk is the measure of expected losses caused by a hazard event occurring in a specific area over a given time period.

Endogenic Movements

• Slow movements (also called diastrophic movements) and sudden movements are the two types of Endogenic Movements.
• The endogenic movements that move, elevate, or build up portions of the Earth’s crust are collectively known as diastrophic movements.
• The processes that cause the upliftment of a large portion of the Earth’s crust are called epeirogenic movements.
• The processes that cause the formation of mountains are called orogenic movements.
• Endogenic forces caused sudden movements like volcanic eruptions and earthquakes.
• The openings in the lithosphere through which molten rock material, gases, ash, pyroclastic materials (rock fragments), dust, and water vapour erupt to the surface of the Earth are called volcanoes.
• The reason for earthquakes is the friction between lithospheric plates.
• Three types of waves are generated from the focus of an earthquake. Primary waves, secondary waves, and surface waves.
• Severe earthquakes that occur on the ocean floor cause giant waves, which can rise up to several metres. These giant waves are called tsunamis.

Exogenic Movements

• The Exogenic forces are responsible for various processes that operate on the surface of the Earth,
  such as weathering, erosion, transportation, deposition, and mass wasting. These processes are collectively known as Exogenic movements.
• Each exogenic process derives its energy from different external forces, which are called the driving forces of exogenic movements.
• The processes that bring about these chemical and mechanical changes in rocks are called weathering.
• Physical, Chemical and Biological weathering are the three types of Weathering.
• Varied landforms are created by the continuous processes carried out by external agencies like running water, wind, glaciers, sea waves, etc. Hence, these agencies are often called geomorphic agents.
• The process by which running water, glaciers, wind, and waves move rock fragments from one place to another is called erosion and transportation.
• These materials will be deposited in low lying regions and this process is called deposition.
• In addition to weathering and erosion, another type of earth movement that occurs on the surface of the Earth due to exogenic forces is mass wasting.
• ‘Urulpottal’ is a type of mass wasting.
• The sudden movement of rock debris and soil mixed with water down a steep slope under the direct influence of gravity is called a debris flow.

EARTH MOVEMENTS
• The movements that cause the ups and downs on the surface of the Earth are called the Earth movements.

Many geographical phenomena and natural disasters occur in connection with Earth movements. The Earth’s surface is constantly subjected to many changes. For millions of years, numerous movements and resulting processes have been occurring on the surface as well as within the Earth. Each and every landform on the Earth’s surface is formed as a result of these movements and processes. Mountains, plateaus, valleys, rivers, and so on were all created due to these continuously occurring Earth movements and processes.

Types of Earth Movements and the forces that cause them

Convection Currents
Inside the Earth, heat increases with depth. The presence of radioactive elements causes temperature variations in the mantle. Due to this thermal variation, magma in the mantle gets heated and moves upward toward the crust. As it nears the crust, it cools and sinks back down. The magma then heats up again and rises toward the crust. This continuous cyclic movement of magma in the mantle, driven by thermal variations, is called convection current. Eg: Boil some water in a beaker and place small pieces of paper in it. By observing the movement of the paper pieces, we can understand that the layer of water at the bottom of the beaker gets heated up and rises. As it reaches the surface, it cools and sinks back down.

This simple experiment helps us understand how the magma in the Earth’s mantle moves in a similar cyclic manner due to thermal variations.

Hazards and Disasters

• A hazard is generally referred to as a situation that poses a threat to life, health, property, services, socio-economic stability, or the environment.
• A disaster can be defined as a serious disruption in the functioning of a community or society that causes widespread material, economic, social, or environmental losses, and exceeds the ability of the affected society to cope using its own resources.
• A hazard is a physical event that has the potential to trigger a disaster; however, such a physical event itself need not necessarily result in a disaster. For example, an earthquake in an uninhabited desert cannot be considered a disaster, no matter how strong its intensity is.
• Hazards may be either man-made or naturally occurring. If a community i s incapable of coping with a hazard effectively, it can escalate into a disaster.
• Risk is the measure of expected losses caused by a hazard event occurring in a specific area over a given time period.
• In the context of disasters, vulnerability can be defined as the extent to which a community, structure, service, or geographic area is likely to be damaged or disrupted by the impact of a particular hazard.
• Capacity refers to the resources, means, and strengths within a community that enable it to cope with,
  withstand, prepare for, prevent, mitigate, or quickly recover from a disaster.

ENDOGENIC MOVEMENTS
Earthquakes, volcanism, orogenic movements, epeirogenic movements, and plate tectonics are the result of endogenic movements. We can classify them into slow movements (also called diastrophic movements) and sudden movements.

DIASTROPHIC MOVEMENTS
The endogenic processes that move, elevate, or build up portions of the Earth’s crust come under diastrophism.

• The endogenic movements that move, elevate, or build up portions of the Earth’s crust are collectively known as diastrophic movements.
• The processes that cause the upliftment of a large portion of the Earth’s crust are called epeirogenic movements. These movements cause only minimal deformation on the Earth’s surface, whereas in orogenic movements, the Earth’s surface is severely deformed.
• The processes that cause the formation of mountains are called orogenic movements. Fold mountains are formed through the folding of crustal portions.

Horst and Graben
The uplifted block of the Earth’s crust formed due to faulting is called a horst (block mountain). The corresponding down-dropped block of the Earth’s crust is called a graben.

SUDDEN MOVEMENTS
• Endogenic forces caused sudden movements like volcanic eruptions and earthquakes. These events often turn disastrous, leaving a trial of widespread devastation on the surface of the earth.

Volcanoes
The outermost layer of the Earth, called the crust, along with the uppermost portion of the mantle, together form the lithosphere with an average thickness of 100 kilometres. A zone lying just bplow the solid lithosphere called the asthenosphere, where rocks exist in a partially molten (semi-liquid) state. It is from this zone that molten rock material, called magma, rises to the surface of the Earth through holes, cracks, and weaker portions of the lithosphere. It is from this zone that molten rock material, called magma, rises to the surface of the Earth through holes, cracks, and weaker portions of the lithosphere. The openings in the lithosphere through which molten rock material, gases, ash, pyroclastic materials (rock fragments), dust, and water vapour erupt to the surface of the Earth are called volcanoes. The materials that erupt in this way are known as volcanic materials. The molten rock material present in the upper mantle is called magma. Once it starts moving towards the crust or reaches the surface, it is referred to as lava.

Earth’s lithosphere consists of seven major plates and several minor plates, as explained by theory of Plate Tectonics. The major volcanic zones are mainly located along plate margins.

Volcanoes and Human Life

• Volcanic explosions near human settlements cause loss of lives and destruct properties.
• They disrupt economic activities and severely affect human life.
• The lava flow following a volcanic eruption adversely impacts both nature and human settlements. By destroying houses and land, it leaves many people homeless and jobless.

volcanic eruptions cause immeasurable damage. Around 36,000 people lost their lives due to the Krakatoa volcanic eruption in 1883. Most of Krakatoa Island, located between Java and Sumatra in Indonesia, collapsed into the sea after the eruption.

Lava, ejected out from a volcano flow like a river and bums everything in its path and leaves behind a black layer covering all the areas it passes through. Still people prefer to live in volcanic regions even though volcanoes are dangerous. Because the ash from volcanoes and the soil formed by the disintegration of rocks created from solidified lava are very fertile. Such places are suitable for agriculture and hence attract people to settle there.

Methods to reduce the intensity of the disasters:
Can’t prevent the eruption of volcanoes. However the intensity of it can be reduced by using scientific methods in identifying such areas and by taking precautionary measures.

• Avoid the constmction of houses in areas close to volcanoes.
• Restrict tourism in such areas.
• Continuously monitor volcanic regions using scientific instruments and issuing early warnings.
• Construct buildings capable of withstanding lava flow and ash fall after an eruption.

Other ways in which volcanic activities are useful to humankind

• The geothermal energy released from volcanic regions is converted into electricity in certain areas and utilized for local purposes.
• Lava is rich in minerals, and many valuable minerals reach the surface of the Earth through the flow of lava.
• Volcanic regions often attract a large number of tourists.

Volcanism

Volcanism is the process that includes the formation of magma, the movement of magma and other pyroclastic materials toward the surface, their emption through holes and cracks in the lithosphere, explosions caused by the emption, lava flow, solidification of magma, the formation of various igneous landforms, and all other associated processes. Volcanoes are landforms created on the Earth’s surface by molten rock material that reaches the surface. They differ in size and shape. Based on the nature of eruption and the formations created on the Earth’s surface, volcanoes are classified as shield volcanoes, composite volcanoes, and calderas. Vast basalt flood plains are also formed when lava floods over an extensive area. The Deccan Province in India is an example of this type. There are thousands of volcanoes found both on land and on the floor of the oceans.

Earthquakes
The reason for earthquakes is the friction between lithospheric plates. When two lithospheric plates move past each other, friction is generated along their margins. This friction in a way restricts the movement of the plates, causing high tension to build up along the margins. As a result, energy gets concentrated in these areas. When the pressure of the plates to move overcomes the friction at the plate boundaries, a sudden movement or rupture occurs at the plate boundaries. This causes energy to be released abruptly. This energy travels to the surface as seismic waves, which are experienced as earthquakes.

Such types of earthquakes are called tectonic earthquakes. The point inside the Earth from which the energy is released is called the focus or hypocentre. The point on the Earth’s surface directly above the focus is called the epicentre. The epicentre is closest to the hypocentre, and it is this point that seismic waves reach first.

Earthquakes occur not only because of tectonic movements but also due to volcanic eruptions, the collapse of mine roofs in intensive mining areas, and explosions. In places where lafge reservoirs are situated, minor tremors are often caused by faults in the bedrock due to the pressure exerted by the water on the bedrock.
Eg: Minor tremors often occur in the Idukki District. They are of this type.
It is next to impossible to predict earthquakes very accurately or to completely prevent the subsequent disasters. However, we can mitigate the intensity of disasters caused by earthquakes by adopting precise preventive measures and by raising awareness.

Earthquake waves
Three types of waves are generated from the focus of an earthquake. Primary waves, secondary waves, and surface waves. Among these, surface waves are the most destructive.

The scale devised by Charles F. Richter in 1935 to measure an earthquake’s magnitude is called the Richter scale. The instrument that records earthquake waves is known as a seismograph. By measuring the amplitude of the recorded seismic waves, the magnitude of an earthquake can be determined. Small, local tremors are usually measured using the Richter scale, while large earthquakes are recorded using a more precise measurement known as the Moment Magnitude Scale. Following an earthquake, seismic waves radiate in all directions from the focus. However, at certain distances from the focus, there are places where these waves are not recorded. Such areas are called the shadow zones of an earthquake.

Tsunami
Severe earthquakes that occur on the ocean floor cause giant waves, which can rise up to several metres. These giant waves are called tsunamis. The impact of volcanic eruptions on the ocean floor and the fall of meteors can also cause tsunamis. It is the coastal areas that mainly bear the brunt of tsunamis. Tsunami warning systems are widely used today with the help of modern technologies.

• The National Oceanic and Atmospheric Administration (NOAA), using satellite communication systems, has installed Deep-ocean Assessment and Reporting of Tsunamis (DART) stations at many locations to detect and monitor tsunami activity.

A strong earthquake with a magnitude of 9.1 occurred in the Indian Ocean, southwest of Aceh Province in Sumatra, on 26 December 2004. It triggered a tsunami that caused widespread devastation along many coasts, including the coast of Kerala.

Methods to safeguard ourselves from tsunamis:

• If the sea level suddenly goes down by several metres, consider it a tsunami warning. Run away from the shore immediately and move to higher ground.
• If you are caught in a tsunami, try to save yourself by holding onto something that can float.
• Always listen to official tsunami warnings on the radio, TV, or mobile and follow evacuation instructions immediately.

EXOGENIC MOVEMENTS
• The Exogenic forces are responsible for various processes that operate on the surface of the Earth, such as weathering, erosion, transportation, deposition, and mass wasting. These processes are collectively known as exogenic movements.
Each exogenic process derives its energy from different external forces, which are called the driving forces of exogenic movements. The nature and rate of these movements vary according to the climatic regions of the Earth.

WEATHERING
The Earth has different types of rocks, and they have been subjected to various changes over a long period of time. Because of certain exogenous forces, rocks are mechanically disintegrated or chemically decomposed.

• The processes that bring about these chemical and mechanical changes in rocks are called weathering.

Benefits of humans from the weathering of rocks:

• Weathering leads to the formation of soil
• It helps to separate minerals from rocks
• It causes mineral enrichment
• It makes mining easier

EROSION, TRANSPORTATION, DEPOSITION
Rock fragments formed by weathering or other processes are moved from one place to another by running water, glaciers, wind, and waves.

• Varied landforms are created by the continuous processes carried out by external agencies like running water, wind, glaciers, sea waves, etc. Hence, these agencies are often called geomorphic agents.
• The process by which running water, glaciers, wind, and waves move rock fragments from one place to another is called erosion and transportation.
• These materials will be deposited in low lying regions and this process is called deposition.

MASS WASTING
• In addition to weathering and erosion, another type of earth movement that occurs on the surface of the Earth due to exogenic forces is mass wasting.

It refers to the movement or fall of rock fragments or earth materials down a slope under the direct influence of gravitational pull. It ranges from very slow movements to rapid movements. Mass wasting can vary from the sliding of a very thin layer of soil to the fall of large quantities of earth materials.
The rock side induced debris flow, locally called ‘Urulpottel’ that occurred on 30th July 2024, causing an unparalleled catastrophe in the district of Wayanad, is also a type of mass wasting.

Debris flow in Kerala

The state of Kerala, because of its geographical peculiarities, is prone to multiple hazards. The common natural hazards that occur in Kerala are sea incursion (flooding of seawater onto the land) along the coastal region in the west of the state, and landslides and debris flows in the Western Ghats in the east. The increase in population density, unscientific construction methods, and the overexploitation of natural resources turn natural hazards into major disasters. The uneven and heavy rainfall caused by climate change becomes a triggering factor for these disasters. In recent years, the rainy season has become synonymous with fear and disaster in Kerala. In this scenario, it is highly necessary to scientifically analyse the disasters that occur in Kerala, adopt precautionary measures, and make people aware of them.

Urulpottal

• ‘Urulpottal ’ is a type of mass wasting.
• The phenomenon of the fall or movement of rocks or topsoil from higher to lower areas under the direct influence of gravity is called mass wasting.

Landfalls, rockfalls, landslides, debris flows, and land subsidence are different types of mass wasting seen in highlands. The sudden movement of rock debris and soil mixed with water down a steep slope under the direct influence of gravity is called a debris flow. The landslide refers to the downward sliding of a portion of a mountain slope under the force of gravity. In the hilly regions of Kerala, intense rainfall often triggers landslides or debris flows, which may occur either separately or in combination. This phenomenon is locally known as ‘ Urulpottal’ and can often be highly destructive.

The possible factors that can lead to ‘Urulpottal’ in an area are the slope of the land, the depth and structure of the soil, land use, and the distribution of streams. Heavy rainfall, cloudbursts, and earthquakes arc the main triggering factors for debris flow. In addition to these, unscientific rock quarrying during the monsoon season and the unscientific construction activities can also act as triggering factors. Areas with a slope of more than 22 degrees have a higher possibility of experiencing debris flow/landslide.

Debris flow and landslides are generally common in the Western Ghats and Himalayan mountains. It is estimated that the highlands of Kerala experience widespread major and minor landslides or debris flows, soil piping, and landfalls.

Soil Piping or Tunnel Erosion

A phenomenon recently observed in hilly areas with laterite is soil piping. In regions where clayey soil is found beneath a laterite cap. water movement can wash away clay that has comparatively less cohesion. This removal of sub-surface soil by water creates underground channels or pipes, and the process is called soil piping. During heavy rain, or due to other causes, water seeps through the pores in the laterite cap and removes the clay-silt mixture from the clayey subsoil in a shape resembling a pipe. The main reason for soil piping is the hydraulic removal of soil from weaker subsurface layers. Studies have shown that well-shaped depressions formed recently in the districts of Idukki and Kannur are the result of this phenomenon.

Before it turns into a Disaster
It is difficult for us to predict natural hazards like debris flow and landslides. However, we can mitigate their impact and intensity by identifying the areas prone to it in advance through scientific methods and by taking precautionary’ measures.

• Studies using tools like remote sensing and Geographic Information Systems (GIS) can help us identify areas that have a higher possibility of ‘Urulpottal’ debris flow or landslide).
• Institutions such as the Geological Survey of India and the National Centre for Earth Science Studies (NCESS) prepare maps of each district showing landslide/debris flow-prone areas. These maps are available on the website of the Kerala State Disaster Management Authority.