Chapter 2: Shaping of the Earth's Surface (Geography)

The internal (endogenic) forces get their energy from the heat inside the Earth.

• Heat from the core and mantle: the Earth's interior is extremely hot. This heat comes partly from the heat left over from the time the Earth was formed and partly from the slow decay of radioactive elements in the rocks.
• Convection currents in the mantle: heat from the core makes molten material in the mantle rise, while cooler material sinks. These circular convection currents push and pull the tectonic plates.
• Movement of plates over the asthenosphere: the semi-molten asthenosphere lets the rigid lithospheric plates slide slowly (a few centimetres a year).
• Pressure inside the Earth: heat and pressure melt rocks into magma, which forces its way up during volcanic eruptions.

The energy comes from the Earth's internal heat (left over from its formation and from radioactive decay), which sets up convection currents in the mantle that move the tectonic plates.

India's physiographic divisions and the internal forces behind them:

Fold mountains (Himalaya) come from plate collision; plateaus from ancient uplift, faulting and lava flows; the plains from subsidence in front of the Himalaya; the islands from subduction and volcanic activity.

Why: an earthquake is a sudden shaking of the ground. Tectonic plates keep moving, but along their boundaries they get stuck. Stress builds up in the rocks until they suddenly break or slip, releasing energy as seismic waves.

Where: earthquakes are frequent along plate boundaries:

• around the Pacific Ocean, the Ring of Fire (Japan, Indonesia, Chile, the west coast of the Americas);
• along the Himalaya, where the Indian plate pushes into the Eurasian plate, so northern and north-eastern India, and Kutch (Gujarat earthquake, 2001), are earthquake-prone;
• along transform boundaries such as the San Andreas Fault (USA) and mid-ocean ridges.

Prediction: the exact time, place and strength of an earthquake cannot yet be predicted. Scientists can only identify earthquake-prone zones (seismic zone maps) and estimate the probability of earthquakes there. Early-warning systems can give a few seconds' warning after an earthquake starts. So the practical answer is preparedness: earthquake-resistant buildings, drills and awareness.

Earthquakes occur where stress built up at plate boundaries is suddenly released, especially around the Ring of Fire and along the Himalaya. They cannot be predicted precisely; we can only map risk zones and prepare.

• The Earth's lithosphere is broken into plates that move over the asthenosphere because of convection currents.
• When the plate map (Fig. 2.3) is compared with the earthquake and volcano map (Fig. 2.4), most earthquakes and volcanoes lie along plate boundaries.
• Convergent boundaries: when an oceanic plate sinks under a continental plate (subduction), the sinking rock melts and forms magma, causing volcanoes and strong earthquakes, as around the Pacific Ring of Fire. Continental collision (Himalaya) causes frequent earthquakes.
• Divergent boundaries: plates move apart, magma rises and forms new crust (Mid-Atlantic Ridge, Iceland), with volcanic activity and mild earthquakes.
• Transform boundaries: plates slide past each other, causing earthquakes but few volcanoes (San Andreas Fault).
• The interiors of plates are generally stable, with few earthquakes or volcanoes.

Earthquakes and volcanoes are concentrated in belts along plate boundaries (Ring of Fire, Himalaya, mid-ocean ridges), because that is where plates collide, separate or slide past each other.

Meander: a loop-like bend of a river in its middle or lower course. The river erodes the outer bank (steep bank) and deposits sediment on the inner bank (bar). When the neck of a loop is cut through, the abandoned loop becomes an oxbow lake.

Delta: a triangular or fan-shaped landform at the mouth of a river, formed when the river deposits its sediments as it enters the sea. The river splits into many distributaries, with islands (bars) between them. Example: the Ganga–Brahmaputra (Sundarbans) delta.

Label the meander with: river flow, steep bank (erosion) on the outer bend, bar (deposition) on the inner bend, oxbow lake. Label the delta with: river, distributaries, islands/bars, sea.

Deforestation (cutting down forests) speeds up soil erosion:

• Roots hold soil: tree and plant roots bind soil particles. When trees are cut, the soil becomes loose and is easily washed or blown away.
• Cover from rain and wind: leaves and branches break the force of falling rain and slow the wind. Bare ground is hit directly, so more topsoil is removed.
• Faster run-off: forests soak up rainwater and slow it down. Without them, water runs off steep slopes quickly, carrying soil and causing gullies, landslides and floods.
• Wind erosion: in dry areas, removing vegetation exposes loose soil to strong winds, leading to dust storms and desertification.
• Effects: loss of fertile topsoil and lower crop yields, silting of rivers and dams, more landslides in hill areas.

Afforestation, terracing, contour bunding and check dams are ways to reduce this erosion.

Trees bind and cover the soil; when forests are cleared, rain, run-off and wind remove the topsoil much faster, so deforestation increases erosion.

A sample plan (adapt it to your area):

Survey the problem spots, cover the soil with vegetation, treat slopes (terraces, bunds, trenches), slow run-off (check dams, drains) and stop harmful practices, with regular monitoring.

The answer depends on where you live. Examples:

• Hilly regions (Himalaya, Western Ghats): landslides, avalanches, flash floods, cloudbursts, GLOFs.
• Earthquake zones (northern and north-east India, Kutch): earthquakes.
• Dry regions (Rajasthan, parts of Gujarat and Haryana): dust storms, droughts, heat waves.
• River plains and coasts: floods, cyclones, coastal erosion.

Sample mitigation plan (for a landslide-prone hill town):

• Before: avoid building on steep, unstable slopes; plant trees; build retaining walls and proper drainage; follow warnings from the IMD and local authorities; keep an emergency kit.
• During: move away from the path of the slide to stable high ground; do not cross flooded streams.
• After: stay away from the slide area (more slides may follow), help rescue teams, report blocked roads and damaged lines.

Identify the disasters likely in your area (e.g. landslides, earthquakes, floods, dust storms) and plan what to do before, during and after them.

Landforms to show (karst topography in limestone areas): caves, stalactites (hanging from the cave roof), stalagmites (rising from the floor), pillars/columns (where they join), sinkholes (dolines) and an underground river.

Materials: a cardboard box or tray, clay or play-dough, plaster of Paris or papier-mâché, paints, a small mirror strip or blue paper for water, labels.

Steps:

• Make the land surface in clay with one or two shallow sinkholes.
• Cut the front of the box to show a cross-section of a cave below the surface.
• Hang cone-shaped stalactites from the cave roof and fix stalagmites on the floor; join one pair to make a pillar.
• Show an underground river flowing through the cave and a cave mouth.
• Label each landform and write one line on how it forms (water containing carbon dioxide dissolves limestone; dripping water deposits calcium carbonate).

Indian examples to mention: Borra Caves (Andhra Pradesh), Mawsmai Cave (Meghalaya), Belum Caves (Andhra Pradesh).

Show a cross-section of limestone with a cave, stalactites, stalagmites, a pillar, sinkholes and an underground river, each labelled with how it forms.

Before an earthquake:

• Live in buildings that follow earthquake-resistant building codes; fix heavy furniture, shelves and gas cylinders to walls.
• Keep an emergency kit: water, dry food, torch, first-aid kit, whistle, medicines, copies of documents.
• Know the safe spots (under a strong table, against an inside wall) and the open area for assembly; take part in drills.

During an earthquake:

• Drop, cover and hold on: get under a sturdy table and hold it; protect your head and neck.
• Stay away from windows, glass, heavy furniture and electric wires. Do not use lifts.
• If outdoors, move to an open space away from buildings, trees and poles.

After an earthquake:

• Expect aftershocks; leave damaged buildings carefully by the stairs.
• Turn off gas and electricity if there is damage; do not light matches.
• Help the injured, listen to official announcements and avoid spreading rumours.

Prepare before (safe buildings, secured furniture, emergency kit, drills), "drop, cover and hold on" during, and move out carefully, beware of aftershocks and follow official advice after.

This is a map activity. How to do it:

• Take an outline map of India (or the world).
• From newspapers and trusted news websites (and the National Disaster Management Authority, NDMA), list this year's landslides, avalanches, GLOFs, flash floods, earthquakes and dust storms, with the place and date.
• Mark each event with a symbol (for example ▲ landslide, ✱ avalanche, ≈ flood/GLOF, ● earthquake, ∴ dust storm) and number it.
• Add a key (legend) explaining the symbols, and a short table: place, date, disaster, main cause.
• Observe the pattern: landslides and avalanches cluster in the Himalaya and Western Ghats, dust storms in the north-west, earthquakes along the Himalaya and north-east.

Collect this year's events from reliable news sources, mark them with symbols and a key on an outline map, and note where each type of disaster is concentrated.

A guide for the poster:

• Choose landforms: a mountain or hill, river, lake, cave, waterfall or confluence that is sacred or important in your region.
• Examples from India: Kailash–Mansarovar; the Ganga and its sangam at Prayagraj; Govardhan hill (story of Krishna lifting the hill); Amarnath cave; Arunachala hill (Tiruvannamalai); Pushkar lake; Sabarimala hills; Loktak lake in Manipur.
• For each landform: a picture or drawing, its name and location, how it was formed (river deposition, folding, solution of rock, etc.), and the folk story or belief linked to it, collected from elders or books.
• Add a message: why we should protect these landforms (they support water, forests and livelihoods, and our culture).

Make a poster with pictures, location, a line on how each landform formed, and the folk story about it, ending with a message on conserving these places.

Use this format (example: the Kedarnath flash flood, Uttarakhand, June 2013):

Collect information from elders, newspapers and reliable reports, and add photographs or a map.

Record the disaster's place and date, causes, and its effects on lives, transport, farming, trade and tourism, along with the response and the lessons learnt.

Translate the poster's messages carefully, keeping the safety steps in the same order. A sample in Hindi:

Translate each line of the poster faithfully into your language (sample Hindi lines above) and put it up where your family can see it.

Suggested content for each group:

Each group should explain the landforms made by its agent, the causes and impacts of related disasters, and practical mitigation measures, using Indian examples.