The sea is salty because of the presence of dissolved salts in the water. These salts come from a variety of sources, including rivers, volcanoes, and underwater vents.
Over time, rainwater and snowmelt dissolve minerals and other substances from rocks and soil, carrying them into rivers and eventually into the sea. Volcanoes and underwater vents also release minerals and other substances into the ocean.
The most common salt in seawater is sodium chloride, which is also known as table salt. Other salts found in seawater include magnesium, calcium, and potassium. These salts make up about 3.5% of the total weight of seawater.
The concentration of salt in seawater can vary depending on a variety of factors, including the location, temperature, and depth of the water. In areas where there is high evaporation and low rainfall, the concentration of salt can be higher, leading to saltier water.