Earth’s internal composition and Landforms — Social Science STD 7 — Question
Gujarat BoardEnglish MediumSTD 7Social ScienceEarth’s internal composition and Landforms4 Marks
Question
Explain the alluvial (river) land- forms.
✓
Answer
Alluvial landform : When the running water of a river tumbles with great force Over the solid (hard) rocks in a steep sloped valley, or in a low-lying land, its flow is called a waterfall.
When a river enters a plain, it flows in a zigzag path.
The larger zigzag paths (or bends) of a river are known as 'meanders'. The river continuously carries erosion and deposition on the banks of the meanders.
In due course of time, when these meanders come closer, they form a shape which resembles a horse-shoe or a circle. At this stage of the river,
when the river is flooded, the land parts between the meanders are cut-off by the deposition of the river flow and the river takes to straight path abandoning the longer path.
The water remains in the abandoned cylindrical part of the river.
As a result, a lake is formed there which is known as Ox-bow lake.
When the large rivers are flooded during rainy season, it forms a fertile plain on either banks of the river by depositing alluvium and other material, which is called When a large amount of silt is deposited on both sides of the river, the raised banks are called 'Levees'.
The flow of the river becomes slow as it approaches a sea ocean. Due to its slow flow, it deposits the alluvium which it brings along with it in the form of sand, clay and other matter.
Due to this the flow of the river is divided into many streams and distributaries.
Each distributary forms its own river mouth. Due to the collection of all sediments of all river mouths, a very fertile Delta is formed.
Glacial landforms : High latitudes or high mountainous regions remain snow-clad throughout the year.
The snow accumulated on the high slopes of the mountains gradually starts moving towards lower slopes.
This gradual flow of moving snow is called 'Glacier'.
The glacier erodes by bulldozing, rocks, etc.
to expose the solid rock below, and forms a specific landscape. Besides, the glacier forms 'U' shaped valley. It also forms deep gorges. In the mountainous regions, the ice (snow) in these gorges melts and water is filled in these gorges. This results in the formation of beautiful lake called ‘Tarns'.
The glacier brings small and large rock particles, sand, pebbles, etc. along with it and deposits them. Due to such deposits, the glacier forms a hillock-like landform in the middle of its flow which is called 'Drumlin'.
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