Landforms and disasters

Landforms give us water, soil, homes and beauty. But each kind of landform also has its own disaster. The book looks at four. For each, ask three questions: what causes it, where it happens, and how to reduce the harm.

1. Landslides (bhuskhalan): a slope suddenly gives way.

• Heavy, continuous rain is a main cause: water soaks into soil and rock, making them heavier and more slippery.
• Earthquakes and volcanic eruptions shake and weaken slopes.
• Steep slopes and loose, weathered rock add to the risk.
• People add to it too: cutting forests, mining, building roads and houses on hillsides without planning, and poor drainage that lets water collect.

2. Avalanches (himskhalan): snow suddenly slides down a steep mountain slope.

• Heavy snowfall in a short time adds weight, especially on top of weak, loose layers of snow.
• A sudden warm spell partly melts the snow and loosens it.
• Strong winds pile snow up unevenly.
• Earthquakes and vibrations, and people skiing, trekking or building in the mountains, can set it off.

3. GLOFs, Glacial Lake Outburst Floods. Picture a lake of melted glacier water held back by a weak wall of ice or loose moraine.

• Rising temperatures melt glaciers faster, so the lake gets bigger and presses harder on its wall.
• Heavy rain or snow adds more water.
• An earthquake, avalanche or landslide can hit the lake or break the wall.

The wall bursts, and all the water rushes down at once, causing a destructive flood downstream.

4. Dust storms: strong winds lift huge amounts of loose, dry soil and sand into the air.

• Long droughts and low rain dry out the soil.
• They are common in desert and semi-arid (fairly dry) regions.
• Land left bare by cutting trees, overgrazing (too many animals eating the grass) or poor farming is easily blown away.
• Climate change can make dust storms more frequent and stronger.

Notice a pattern: in all four, nature starts the disaster, but human actions can make it worse. That also means human actions can make it less bad.

Mitigation means reducing the harm before a disaster strikes. For each disaster, the book asks you to find the prone areas, mitigation measures and recent examples from newspapers, atlases and books. Ideas to start from: plant and protect trees and grass on slopes; build proper drains; avoid building on steep, loose slopes; watch glacial lakes; give early warnings; and practise drills. The landslide poster (Q14) lists what to do before, during and after a landslide.

The whole chapter in one picture: forces inside the Earth (earthquakes, volcanoes, folding, faulting) build mountains, valleys and ocean basins. Forces outside (weathering, erosion, deposition, by running water, waves, glaciers, wind and underground water) wear them down and reshape them. Our lives depend on these landforms, so understanding them helps us prepare wisely for disasters.