From a vastcosmicscale, Earth is not a brown landmass, but a dazzling 'blue marble.' This captivating blue originates fromthe hydrosphere— a continuous yet irregular layer of matter.

From a microscopic perspective,the periodic tablehydrogen and oxygen precisely combine to form H₂O, forming a fundamental level in the material world. The total amount of water on Earth reaches approximately 1.4 billion cubic kilometers, withthe oceanscovering about 71% of Earth’s surface, trapping around 96.54% of the world’s water. Meanwhile, the freshwater essential to our survival accounts for only about 3% of this vast total, highlighting its scarcity.freshwaterThis small proportion underscores the preciousness of freshwater resources.

The Rhythm of Physical and Chemical Properties

• Salinity: Refers to the total mass of dissolved salts in 1 kg of seawater. It is regulated by factors such as precipitation, evaporation, and runoff.
• Temperature Distribution: As shown above, surface ocean temperature decreases with increasing latitude. Low-latitude regions absorb more solar radiation, resulting in higher temperatures, while high-latitude areas are colder.
• Source of Materials: Salts in seawater primarily originate from river runoff inputs, erosion of seafloor rocks, and active submarine volcanic activity.