EARTHQUAKES AND VOLCANIC ERUPTIONS
WHAT ARE EARTHQUAKES AND VOLCANOES?
A volcano is a vent (opening) in the Earth’s crust through which molten material erupts suddenly.
Earthquakes are sudden vibrations caused by the movement of the Lithospheric plate
Define 'Stacks'
When erosion breaks the roof of a sea arch, only the wall-like features are left standing in the water. These are called stacks
As a river approaches the sea, it breaks up into several smaller channels called _______.
DISTRIBUTARIES
WHAT IS A SAND DUNE?
When the wind blows, it lifts and transports sand. When the wind stops or hits an obstacle (like a bush or a rock), the sand falls and gets deposited in a pile.
how are volcanoes and earthquakes formed? two points each.
Deep inside the Earth, the temperature is so high that rocks melt into magma.
When pressure builds up inside the Earth, this magma is pushed upward. It finds a weak point or an opening in the crust and erupts onto the surface.
Once magma reaches the surface, it is called lava.
EARTHQUAKES
When the Lithospheric plates move, the surface of the Earth vibrates. These vibrations can travel all round the Earth.
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The Focus: The place in the crust where the movement starts is called the Focus. This is deep underground.
The Epicenter: The place on the surface directly above the focus is called the Epicenter.
What is the primary cause of coastal landforms?
The erosion and deposition of sea waves give rise to various coastal landforms.
How is an Ox-bow Lake formed?
When a meander loop gets cut off from the main river due to continuous erosion and deposition, it forms a curved lake called an ox-bow lake.
explain the difference between a sand dune and loess
Sand Dunes Large, heavy grains of sand. Deposited close to the source as wind cannot carry heavy sand far.Common in deserts (e.g., Thar Desert).
Loess. Very fine, light, and dust-like particles.Carried over very long distances by wind before being deposited. Found in large areas of China and parts of Europe.
"If the Lithospheric plates are constantly moving, why don't we feel earthquakes every single day in every part of the world? Furthermore, explain why some volcanic eruptions are considered 'constructive' for the Earth's surface despite being destructive to human life."
Most plate movements are very slow (a few centimetres per year), so they do not produce sudden shocks.
Energy is released gradually along many plate boundaries, preventing strong vibrations.
New Landform Creation: Islands like Hawaii or Iceland were formed entirely by volcanic activity.
Soil Fertility: Volcanic ash and lava weather down over time to form Black Soil (Regur soil). This soil is incredibly rich in minerals like iron, magnesium, and potassium, making it some of the most fertile land for agriculture in the world.
The landscape of a coastline is never permanent. Explain the sequence of erosional stages that transform a solid rocky cliff into sea caves, arches, and finally stacks. How does this process reflect the power of sea waves as an agent of gradation?"
The process begins when sea waves continuously strike against coastal rocks.
Formation of Sea Caves: As the waves continue to strike these cracks, they become larger and wider. Eventually, hollow, door-like cavities are formed
Development of Sea Arches: Continuous erosion by the waves further enlarges these cavities. Eventually, the waves break through the back of the cave, leaving only the roof of the rock standing.
Stacks: As erosion continues, the roof of the sea arch becomes too heavy or thin to support itself and eventually collapses. This leaves only the vertical, wall-like segments of the rock standing
"A group of farmers living near a large river noticed that every year during the monsoon, the river banks seem to get higher, and the surrounding fields become more fertile. However, they also noticed that the river is starting to curve more than it did ten years ago. Using your knowledge of the 'Work of a River,' explain these two phenomena."
Formation of Levees and Floodplains (3 Marks)
The Process: When the river overflows during the monsoon, it carries fine soil and sediments called alluvium. As the water spills over the banks, it loses speed and drops the heavier sediments right at the edge.
These deposits create natural raised banks called Levees.
Formation of Meanders (3 Marks)
The Process: As a river flows through the flat plains, its speed is lower than in the mountains. Instead of flowing straight, it begins to erode the outer banks of its channel and deposit sediment on the inner banks.
This continuous process of erosion and deposition causes the river to twist and turn into large loops known as Meanders.
"Nature uses different tools to shape the Earth depending on the environment. Compare the role of a glacier as a 'moving river of ice' with the role of wind as an 'invisible sculptor' in deserts. How do their processes of erosion and deposition differ in the landforms they create?"
Glaciers are massive bodies of ice that move due to gravity, acting like "rivers of ice" that carve the land. In contrast, wind is an atmospheric force that is most effective in arid (dry) regions where there is little vegetation to hold the soil.
Glaciers erode the landscape by "bulldozing" rocks and soil. They carve out deep hollows. As the ice melts, these hollows fill with water, becoming beautiful Lakes in the mountains.
Wind erodes the lower section of rocks more than the upper part. This process creates Mushroom Rocks, which have narrow bases and wider tops, looking like a mushroom.
When a glacier melts, it can no longer carry its heavy load. It deposits materials like big rocks, sand, and silt. these deposits form Glacial Moraines.
When the wind stops blowing, it drops sand in low hill-like structures called Sand Dunes. If the sand is very fine and light, it is carried over long distances and deposited in large areas called Loess.
A construction company is planning to build a high-rise apartment complex and a school in two different locations: one is near a known 'Plate Boundary' in the Himalayas, and the other is near an 'Extinct Volcano' in the Deccan Plateau."
Explain how the building design should be modified to ensure safety.
Analyze whether building near an 'extinct volcano' is safe. What is the difference between an extinct volcano and a dormant one?
To ensure safety, the company must use Earthquake-resistant building techniques. This includes using flexible materials, deep foundations, and "base isolators" (shock absorbers) that allow the building to vibrate without collapsing when the seismic waves pass through the epicenter.
Building near an Extinct Volcano is generally considered safe because these volcanoes have not erupted for thousands of years and are not expected to erupt again.
Extinct Volcanoes have no magma supply and are unlikely to ever erupt again.
Dormant Volcanoes are "sleeping"; they haven't erupted in a long time but still have the potential to become active in the future.
The work of sea waves is a constant battle between destruction and construction. Analyze this statement by explaining the transformation of coastal landforms. Why do stacks eventually disappear, and how does the sea 'compensate' for the land it destroys?"
Erosion (destructive) and Deposition (constructive). They shape the coastline by wearing away solid rock and building new landforms elsewhere.
The work of the sea is a cyclical process. The material "stolen" from a cliff by erosion is "gifted" back to the coastline in the form of a beach. This balance ensures that the Earth's crust is constantly being reshaped rather than simply destroyed.
A Stack is not a permanent feature. Continuous wave action at its base (undercutting) and weathering from the top cause it to shorten into a Stump.
Eventually, the stump is eroded below the water level,
Explain how the change in a river's speed from the mountains to the plains leads to the formation of different landforms. Provide three points to support your answer."
1. In the mountains, the steep gradient gives the river high velocity and spectacular waterfalls as it flows over hard rock.
2. As the river enters the flat plains, its speed decreases significantly and it starts eroding sideways creating large winding loops called meanders.
3. By the time the river reaches the sea (the mouth), its speed is at its lowest. It is so "tired" and loaded with fine silt that it cannot carry it further. This leads to the buildup of deltas where the river splits into many distributaries to deposit its remaining load.
"Imagine you are an environmental consultant. You have been asked to compare two different sites for potential development: one near a retreating mountain glacier and another in a sandy desert region. Analyze the risks and features of both sites by explaining the work of ice and wind.
Glaciers carve out the solid bedrock of mountains. Any structure built on the path of a moving glacier would be crushed or "bulldozed" by the ice.
Risks: In the desert, wind is the primary sculptor. The biggest risk here is Sand Dunes. Because dunes are "active," they migrate. A house built today might be buried under a moving sand dune in a few years.
"Imagine you are a Disaster Management Officer. A city is located in a high-risk zone where two tectonic plates meet. In this region, there is also an active volcano nearby. While the residents are afraid of these 'disasters,' the local economy depends heavily on the tourism and agriculture that the volcano provides."
Task:
Explain the relationship between the movement of these tectonic plates and the occurrence of both earthquakes and volcanoes in this specific city.
Compare and Contrast the warning signs of a volcanic eruption versus an earthquake. Why is one easier to prepare for than the other?
As the plates slide past or push against each other, they get stuck. The sudden release of this built-up pressure creates vibrations (seismic waves) that we feel as earthquakes.
The movement of plates can also create gaps,This creates molten magma, to rise through the crust to form a volcano.
Volcanoes usually give "clues" before they erupt. These include small tremors, the swelling of the mountain's sides, and the release of gases or steam from the vent.
Unlike volcanoes, earthquakes have no reliable short-term warning signs. Scientists can identify high-risk zones, but they cannot predict the exact day or time an earthquake will strike.
(Against staying): The risk of a major earthquake (above 7.0 on the Richter scale) or a massive volcanic eruption (pyroclastic flow) poses a constant threat to life and infrastructure
(For staying): The volcanic soil is extremely fertile for agriculture (Black Soil), and the unique landscape attracts tourists, providing jobs and food security that might not be available elsewhere.
Imagine you are a geomorphologist (a scientist who studies landforms) visiting a rocky coastline. You notice a series of landforms including a high vertical rock face, a lonely pillar of rock in the water, and a sandy stretch nearby. Identify these landforms and explain the continuous process of 'Erosion and Deposition' that created them. How might this coastline look 500 years from now?"
The high vertical rock face: Sea Cliff.
The lonely pillar of rock: Stack.
The sandy stretch: Beach.
Sea waves strike the coast with immense force, trapping air in rock cracks. When the water retreats, the air expands explosively, widening the cracks.
Cracks expand into Sea Caves. 2. Caves erode further to leave only the roof, forming Sea Arches. 3. The roof eventually collapses, leaving isolated Stacks.
While waves erode the cliffs, they also carry the broken rock fragments (sediment).
When waves lose their energy near the shore, they drop this sand and gravel.
The accumulation of these sediments along the shoreline forms Beaches.
Future Prediction (500 Years Later)
Cliff Retreat: The coastline will have moved further inland as the Sea Cliff continues to crumble.
Disappearance of Stacks: The current "Stack" will likely have been eroded down into a "Stump" (a small nub of rock) or disappeared entirely under the water.
New Formations: New caves and arches will have formed in parts of the cliff that are currently solid rock.
Imagine you are a geographer comparing two different landscapes: the Thar Desert in Rajasthan and the Northern Plains of India. Both regions have landforms created by 'deposition,' but the agents and results are very different.
Task:
Identify and compare the primary agent of change in each region. (2 Marks)
Analyze one major depositional landform from each region. How is the process of formation similar yet different? (5 Marks)
Evaluate how these depositional landforms affect the lives of the people living there. (3 Marks)"
Identifying the Agents Thar Desert: The primary agent is Wind. In dry regions with little vegetation, wind easily picks up and moves loose particles.
Northern Plains: The primary agent is Running Water (Rivers).
Comparing Depositional Landforms
The Landforms: In the desert, we see Sand Dunes; in the plains, we see Floodplains.
Similarity: Both are formed through the process of Deposition. In both cases, the agent (wind or water) loses its speed/energy and can no longer carry its "load," causing it to drop the sediments.
These landforms are unstable and can move over time.(sanddunes) These landforms are permanent and flat.(flood plains)
In the Northern Plains (Floodplains): The deposition of alluvium makes the soil extremely fertile. This supports intensive agriculture
In the Thar Desert (Sand Dunes): While sand dunes are beautiful, they make life difficult. They are not fertile for crops