Contents of Physical Geography: Lithosphere, Hydrosphere, Atmosphere, and Biosphere
Geography is not merely the description of maps or places—it is the science of understanding the world around us. One of its most important branches is Physical Geography. Over time, with the advancement of scientific research and modern thought, both the definition and scope of Physical Geography have expanded significantly.
The central themes of Physical Geography include the origin and evolution of the Earth, landforms, rocks and minerals, geomorphology, rivers, climate, and soil. Simply put, Physical Geography deals with the natural features and characteristics of our planet.
🔎 The Four Spheres of Physical Geography
Physical Geography mainly revolves around four interconnected spheres:
- Lithosphere;
- Hydrosphere;
- Atmosphere; and
- Biosphere.
These spheres are interrelated and interdependent. Let’s briefly look at each:
🪨 Lithosphere
The Earth’s solid outer layer, or crust, is called the lithosphere. Life has developed upon this surface, shaped by both internal and external forces. As a result, diverse landforms such as mountains, plateaus, and plains have emerged.
The lithosphere not only creates landforms but also provides essential elements for plants and animals. Through soil and minerals, it supports life. In essence, the lithosphere forms one of the fundamental bases of life on Earth.
💧 Hydrosphere
About 71% of Earth’s surface is covered by water. Oceans, seas, rivers, bays, lakes, and other water bodies together form the hydrosphere, which spans nearly 362.5 million square kilometers.
The hydrosphere is vital for sustaining biodiversity. Water evaporates due to solar heat, rises into the atmosphere, forms clouds, and eventually returns to the Earth as rain or snow. This continuous cycle maintains the natural balance of water on our planet.
🌤️ Atmosphere
The atmosphere is the gaseous envelope surrounding the Earth, thousands of kilometers thick. It begins just a few meters above the Earth’s crust and extends up to about 10,000 kilometers.
The atmosphere regulates the climate, absorbs and distributes solar energy, and supplies essential gases like oxygen and nitrogen for living beings. Its density decreases with altitude. Without the atmosphere, life on Earth would not survive.
🐾 Biosphere
The biosphere is formed by the interaction of the lithosphere, hydrosphere, and atmosphere. This is the realm where life exists. Organisms are found up to about 6 kilometers above sea level and as deep as 7 kilometers below sea level—making the biosphere about 13 kilometers thick.
Environmental scientists further divide the biosphere into smaller units called ecosystems. Each ecosystem is a miniature world where plants, animals, and the environment are interconnected.
🔄 Interrelationships Among the Spheres
Although distinct, the four spheres are deeply interconnected:
🌊 From the hydrosphere, living beings obtain water.
🪨 From the lithosphere, they receive minerals.
🌬️ From the atmosphere, they get oxygen and other essential gases.
Together, these create the biosphere, which sustains all life.
Physical Geography teaches us how the Earth was formed and how each element of nature is connected to life. The lithosphere, hydrosphere, atmosphere, and biosphere—together—sustain life on this planet. If we understand and respect nature, we can preserve this delicate balance of Earth.
✍️ Written by: Md. Shahin Alam
🔗 References:
- Singh, Savindra (2009), Physical Geography, Prayag Pustak Bhawan, Allahabad, India.
- Rahman, Mohammad Arifur (2017–2018), Kabir Publications, Dhaka.
- Rauf, Kazi Abdur (2002), Prakritik Poribesh, Sujaneshu Prokashoni, Dhaka.
- Rauf, Kazi Abdur (2011), Prakritik Bhugol Porichiti, Sujaneshu Prokashoni, Dhaka.
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