The Earth is a dynamic planet that is continuously changing due to strong forces. Ankur Sir breaks down the intricate processes that shape our world in a thorough lesson of EduAid’s Classroom, with a particular emphasis on the geography of Earth’s surface changes. Understanding these ideas is essential to knowing the natural world around us, regardless of whether you are a Class 9 student or an inquisitive learner.
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Table of Contents
The Composition of Our World
To grasp how the Earth changes, we need to first explore what it’s made of. Our planet consists of two main parts: the lithosphere, which is the land, and the hydrosphere, which includes all the water. Although many people might believe that land is the most important part, in reality, the hydrosphere covers a whopping 71% of the Earth, while the lithosphere covers the other 29%.
The changes that we see on the surface of Earth are driven by two main types of processes: endogenic and exogenic.
Internal vs. External Forces
Endogenic processes are internal forces that originate from within the Earth. One of these is the movement of tectonic plates, which make up the Earth’s crust. These dynamic, ever-moving plates can collide with each other and cause earthquakes and volcanic eruptions. These events can cause abrupt, dramatic changes, such as volcanic hills and the rise or fall of continents.
On the other hand, exogenic processes are external factors that impact the Earth’s surface. Rivers, glaciers, wind, and rainfall are some of these elements that are primarily impacted by the Sun and the atmosphere. Over time, endogenic forces often build up land, while exogenic forces tend to change and erode it.
The Power of Rivers: Erosion and Deposition
Rivers are among the most significant exogenic factors. They perform three primary tasks: erosion (wearing away land), transportation (carrying materials), and deposition (dropping materials in a new location). Using the Brahmaputra as an example, we can see how rivers shape the landscape by carrying sediment in three different ways: suspended (fine particles floating), dissolved (like salt in water), and rolling (heavy materials like boulders moving along the riverbed).
This movement creates unique landforms:
- Meanders: S-shaped curves in a river caused by lateral erosion.
- Oxbow Lakes: Awhura (horseshoe) lakes, like Deepor Beel, are U-shaped bodies of water created when a meander is severed from the main river.
- Sandbars and Floodplains: During floods, rivers deposit fertile silt, forming sandbars and floodplains known locally as Saporis (such as the well-known Majuli).
- Deltas: Sediment accumulates to create triangular landforms known as deltas at the river’s mouth, where it meets the sea.
Wind: The Desert Sculptor
Wind is the main landscape architect in arid areas. It creates sand dunes in some places and depressions in others by moving sand through a process known as deflation. Other desert characteristics include Yardangs (a word of Chinese origin), which are long ridges sculpted by the wind, and Inselbergs (a German word meaning “isolated islands”), which are steep-sided hills left standing after the surrounding land has eroded.
Glaciers: Rivers of Ice
Glaciers, which are moving masses of ice, sculpt the land in high mountains like the Himalayas and polar regions. Although glaciers move very slowly—typically less than one meter per day—their weight gives them tremendous erosive power. They leave behind deposits known as moraines, which are categorized as lateral (sides), medial (middle), ground (bottom), or terminal (the glacier’s end).
The Impact of Sea Waves
Lastly, our coastlines, which span more than 0.5 million kilometers worldwide, are greatly influenced by the ocean. Sea waves deposit sand and pebbles to form stunning beaches and erode sea cliffs. But the sea also has destructive power; underwater earthquakes can set off tsunamis, which devastate coastal regions.
Conclusion
Knowing these mechanisms enables us to view the Earth as a dynamic, living system. Our planet is continuously changing, from the gradual movement of a glacier to the abrupt tremor of an earthquake. The secret to academic success for students is to grasp these ideas through both textbook study and visual learning.
