Landforms and How They Shape
FoundationMountain ranges, plains, river valleys, plateaus and basins are common landforms; movements of the crust raise mountains from within, while water and wind carve the land from outside.
- Five landforms: ranges, plateaus, plains, valleys, basins.
- Crustal movement is the inner force raising ranges and sinking basins.
- Rivers erode valleys; deposited sediment builds plains.
文體小知識：說明文把大地的面貌一一道來。這一篇帶你認識五種地貌，看看地殼運動、水和風怎樣雕塑地球。
§Text Passage
1Looking down from a plane, you see mountains high and low, winding river valleys, flat plains and round basins. These different shapes of the ground are landforms, works the Earth has spent hundreds of millions of years carving, and every one holds a story of change.
2There are five common landforms: a mountain range is a chain of towering peaks, and linked ranges form mountain systems; a plateau is a broad, elevated tableland; a plain is low and flat, best for farming and cities; a river valley is the strip of low land along a river; a basin is high all round and low in the middle, like a great bowl.
3The shapers of landforms work from inside and outside. Forces within the Earth keep the crust moving: when plates push against each other, rock layers fold and rise into grand mountains and plateaus; sunken crust may become basins. The Himalayas rose from the long push between the Indian and Eurasian plates.
4Outside forces keep retouching the land, and flowing water works hardest. Rivers scour their banks and beds, carrying away broken rock and sand — erosion — which slowly carves valleys and gorges; when the river slows downstream, the sand settles — deposition — gradually building broad deltas and plains.
5Wind is a sculptor too: in dry regions blowing sand wears rock into strangely shaped wind-eroded landforms. Besides, changes of heat, cold and rain crumble rock bit by bit — weathering. The crumbs are carried off and piled up by water and wind, so landforms keep changing through erosion, transport and deposition.
6Inner forces push the ground up and down; outer forces plane down mountains and fill up lowlands — one quick, one slow, together writing the history of the land. Hong Kong, with many hills and little flat ground, is also the result of mountain-building and long years of weathering and erosion. Knowing landforms, we learn to cherish and use every piece of land wisely.
1Summary 重點摘要
Mountain ranges, plains, river valleys, plateaus and basins are common landforms; movements of the crust raise mountains from within, while water and wind carve the land from outside.
2Vocabulary cards Vocabulary
The shape of the Earth's surface, such as mountains, plains and valleys.
A chain of connected high mountains, such as the Himalayas.
Broad, low, flat land, good for farming and cities.
The strip of low land along a river, carved by flowing water.
Broad, high land with a fairly flat top.
Land high all round and low in the middle, like a great bowl.
The shifting and squeezing of crustal plates, raising mountains or forming basins.
The slow breaking up of rock by heat, cold and water.
The wearing away and carrying off of rock by water and wind.
Sand and mud being dropped and piled up downstream or in low places.
3Step by step Steps
- Step 1: Know the five common landformsLandforms are the shapes of the Earth's surface, and five are most common. Mountain ranges are strings of towering, connected peaks; plateaus are like grand stages, broad-topped and high; plains are low, open and fertile, home to the most people and cities; river valleys stretch along a river's banks; basins are ringed by heights and sunken in the middle. Open a map and find where the ranges and plains are — the land becomes clear at a glance.
- Step 2: Meet earth movement, the inner shaperThe Earth's shell is made of plates that creep about underground, pushing, squeezing and pulling one another. When two plates collide, the rock layers fold and rise into grand mountains and plateaus — the Himalayas grew this way and still rise slightly every year. Where the crust sinks, basins may form. Earthquakes and volcanoes are also signs of crustal movement, showing how mighty the underground forces are.
- Step 3: Flowing water carves river valleysFlowing water is the busiest sculptor of the surface. Rivers scour their beds and banks day and night, carrying off rock and sand, so valleys grow ever deeper and wider, forming deep valleys and gorges. Upstream, fast water erodes most strongly; midstream, the river widens and winds. The Three Gorges of the Yangtze and the Grand Canyon are masterpieces of millions of years of erosion. Erosion never rests, and landforms keep changing daily.
- Step 4: Deposition builds the plainsRivers carry the sand and mud washed from upstream; downstream, where the land flattens and the water slows, the load settles on the bed and banks, building alluvial plains; at river mouths the sand piles up into deltas. The North China Plain is the rich soil laid down over ages by the Yellow River and others, which is why farming there thrives and people gather. Deposition is like land reclamation by nature — only far slower.
- Step 5: Wind carving and weatheringIn dry lands with little rain, wind becomes the chief sculptor. Blowing sand wears rock surfaces into strangely shaped wind-eroded landforms. Meanwhile the repeated swing between hot days and cold nights, plus rainwater freezing and expanding in cracks, gradually crumbles rock — weathering. The crumbs are then carried off by water and wind, feeding further erosion and deposition.
- Step 6: Inner and outer forces shape the land togetherInner and outer forces wrestle constantly: crustal movement pushes the ground up and down like a great modelling hand, while erosion and weathering plane down mountains and deposition fills up lowlands like careful polishing. Landforms change ceaselessly in this tug-of-war. Hong Kong, with many hills and winding bays, is the work of ancient volcanic activity and long years of water and weather. On your next hike, study the rocks and hills underfoot and read the story of the land.
5Worked example Example
Example: On a summer trip, Long visits the Himalayas, where the guide says the rock layers hold fossils of sea creatures; he then visits the North China Plain and sees flat land with deep soil. Explain how these two landforms formed, using earth movement and the work of rivers.
- The Himalayas formed as the Indian and Eurasian plates pushed together, folding and raising the rock layers.
- The raised layers were once on the seabed, which is why the mountains hold fossils of sea creatures — proof that the area was once ocean.
- The North China Plain formed just the opposite way: the Yellow River and others carried sand and mud from upstream.
- Downstream the land flattens and the water slows, so the sediment settles, piling up deep, flat, fertile soil over ages.
- So mountains rise by inner crustal movement, and plains grow by outer river deposition — two great shapers at work.
- Answer: The Himalayas are the work of crustal movement: plates pushed together, folding seabed rock layers up into mountains, which is why their rocks hold sea-creature fossils. The North China Plain is the work of river deposition: rivers carried sediment downstream, it settled as the water slowed, and over ages it piled into a deep, flat plain. One rose by inner force, the other grew by outer depositing — a perfect show of the Earth's two shaping powers.
6Common mistakes Mistakes
7Quick check Quick check
Q1Which landform is high all round and low in the middle?
Q2How did the Himalayas form?
Q3What force mainly carves river valleys?
Q4Where does a plain's deep soil come from?
Q5What is the slow crumbling of rock by heat, cold and rain called?
8Recap Recap
- Five landforms: ranges, plateaus, plains, valleys, basins.
- Crustal movement is the inner force raising ranges and sinking basins.
- Rivers erode valleys; deposited sediment builds plains.
- Wind sculpts dry lands; weathering crumbles rock.
- Landforms keep changing under inner and outer forces.