Why is the ocean water always salty? – Times of India

Salt lies in our kitchens, on our dining tables, and in our oceans. But how did it get there? The history of salt dates back to thousands of years. Over millions of years of weathering and erosion have washed minerals from rocks into rivers that eventually carry them to the sea. Volcanic activity and hydrothermal vents also add minerals from the Earth’s crust to the water, contributing to salinity.Salts are then left behind with the evaporation of water from the Earth’s surface, increasing the ocean’s salinity gradually over time.
This essential mineral does more than just add flavor to our foods. Salts play a crucial role in marine ecosystems by keeping marine organisms buoyant and regulating osmoregulation, allowing them to live in salty conditions.
When fresh water from rivers and lakes mixes with the ocean, it also takes salts and minerals with it. The seafloor contains a large number of vents to the ocean’s interior that these salts and minerals go into.Water falls into the ocean, passes under cracks in the crust of Earth which are present deep in the ocean, and heats up by coming into contact with magma. This heated water dissolves salts and minerals from the rocks, just like hot water dissolves table salt or sugar more readily. The seawater takes these dissolved elements into the ocean through the vents.

There are two major sources of salts into the ocean, runoff from the land and openings in the seafloor.

The main source of salts dissolved in seawater and oceans is the rocks on land. Since rainwater is slightly acidic, these rocks get continuously eroded, which introduces ions into the water. Streams and rivers carry these ions through to the sea.
Another source of ocean salts comes from hydrothermal fluids extracted from seafloor vents. Water from the ocean trickles down into cracks on the seafloor and is heated by magma. Heat supports chemical processes, in which water loses oxygen, magnesium, and sulfates and gains metals like iron, zinc, and copper from the surrounding rocks. The hot water now contains metals from these vents. Underwater volcanic eruptions also spill minerals directly into the ocean.

Salt domes also contribute to the saltiness of the ocean:

Salt domes also contribute to the salinity of the ocean. These are enormous salt deposits that take thousands of years to be formed and can be viewed underwater, particularly in areas such as the northwestern Gulf of Mexico.
The two most common ions found in seawater are chloride and sodium, which account for roughly 85% of the dissolved ions, while magnesium and sulfate compose another 10%. Most other ions are present in minute concentrations. Salinity, or the saltiness of seawater, is a result of temperature, evaporation, and precipitation. In general, salinity is lower near the equator and poles and greater at mid-latitudes. Seawater typically has an average salinity of around 35 parts per thousand, which means that 3.5% of its weight is comprised of dissolved salts.

Sea water adds to the ocean’s saltiness

Many salts and minerals dissolved in the ocean are consumed by marine life. For example, the organism absorbs iron, zinc, and copper in this water. Sodium and Chloride, the main contents of table salt are not and thus, accumulate over time making water salty in the sea. Seawater is about 3.5% salty, and this makes it denser than freshwater. Increased density in most aspects makes the objects, people, and animals heavier and more buoyant in seawater.
Salinity differs from one ocean to another. Salinity is lower near the equator and the poles but higher between them. The salinity level in some seas is much higher than the rest of the ocean, like the Mediterranean. Some lakes, such as California’s Mono Lake and the Caspian Sea in Asia, are saltier. In such water bodies that are landlocked, when the salts evaporate, they get left behind, which builds up the salinity level over time. Most of these saline lakes are situated in arid areas with little precipitation and extremely high temperatures.