MCQ Detailed View

The Earth continuously receives energy from the Sun, and this solar energy drives almost every natural process on the planet. When sunlight reaches the Earth’s surface, part of it is absorbed and converted into heat, while some is reflected back into space. The absorbed energy is responsible for heating the surface, driving winds, maintaining temperature, and supporting biological and physical processes.

One of the most important uses of solar energy is powering the hydrologic cycle, also called the water cycle. This cycle includes processes such as evaporation, condensation, precipitation, and runoff. Studies show that about one-third (1/3) of the solar energy absorbed by the Earth’s surface is used in evaporating water from oceans, rivers, lakes, and soil. This evaporation is the first step of the hydrologic cycle.

The water vapor formed rises into the atmosphere, where it cools and condenses to form clouds. Eventually, this condensed water falls back to the surface as rain, snow, or other forms of precipitation. The continuous circulation of water between the surface and atmosphere regulates Earth’s climate and makes life possible.

The remaining two-thirds of absorbed solar energy is mainly used to heat the land and oceans or drive atmospheric circulation such as winds and weather systems. Without this balance, the Earth’s environment would not sustain stable climates or ecosystems.

The hydrologic cycle is essential for agriculture, freshwater supply, and ecological balance. By knowing how much solar energy is invested in this process, scientists can better understand global energy flow and climate systems.

Therefore, about one-third of the solar energy absorbed by Earth’s surface is devoted to driving the hydrologic cycle through evaporation and related processes.