Anyone who has tasted seawater knows how salty it is – it has an average salt content of around 3.5 percent. Some of the salt in the sea is derived from undersea volcanoes and hydrothermal vents, but the majority is derived from the land. Rainwater dissolves minerals and releases salts from rocks on land, which are then carried downstream by rivers to the sea. As the sun warms the sea, water evaporates, but salt remains, making the sea saltier. It is estimated that 4 billion tons of salt enter the sea each year, but the ocean does not become saltier because a similar amount of salt is deposited on the ocean floor each year, ensuring that the salt level is fairly balanced. The saltiness or salinity of the sea varies from region to region. Near the equator, where temperatures are higher, more evaporation occurs, resulting in a higher salt concentration in seawater. Melting ice and heavy rain near the poles dilute seawater, making it less salty. In this article, you will learn why sea water is salty and blue in color.
Why sea water is salty?
The sea water is salty due to two reasons: runoff from the land and openings in the seafloor. Land rocks are the primary source of salts dissolved in seawater. Because rainwater on land is slightly acidic, it erodes rocks. This causes ions to be released into streams and rivers, which eventually feed into the ocean. Many of the dissolved ions are removed from the water by organisms in the ocean. Others are not removed, causing their concentrations to rise over time.
Hydrothermal fluids, which come from seafloor vents, are another source of salts in the ocean. Ocean water seeps into seafloor cracks and is heated by magma from the Earth’s core. A series of chemical reactions occur as a result of the heat. Water tends to lose oxygen, magnesium and sulfates while picking up metals like iron, zinc, and copper from the surrounding rocks. The heated water is released through seafloor vents, carrying the metals with it. Some ocean salts are formed as a result of underwater volcanic eruptions that directly release minerals into the ocean.
Chloride and sodium are two of the most common ions in seawater. They account for approximately 85 percent of all dissolved ions in the ocean. Another 10% of the total is made up of magnesium and sulfate. Other ions can be found in trace amounts. Temperature, evaporation, and precipitation all affect the concentration of salt in seawater (salinity). The equator and poles have low salinity, while the mid-latitudes have high salinity. The salinity is approximately 35 parts per thousand. In other words, dissolved salts account for approximately 3.5 percent of the weight of seawater.
Some mineral ions are removed from the water by marine animals and plants. Over millions of years, the leftover minerals have accumulated in concentration. Salts can also be released into the ocean by underwater volcanoes and hydrothermal vents on the seafloor.
Were the oceans enough salty from the beginning?
The answer is no. The primordial seas were most likely only slightly salty in the beginning. However, as rain fell on the Earth and ran over it, breaking up rocks and transporting their minerals to the ocean, the ocean became saltier over time. Rain replenishes freshwater in rivers and streams, preventing them from tasting salty. The water in the ocean, on the other hand, collects all of the salt and minerals from the rivers that flow into it.
The same amount of salt from ocean water is most likely deposited as sediment on the ocean floor, so yearly gains may offset yearly losses. To put it another way, the ocean today most likely has a balanced salt input and output.
What is Dead Sea and how it is different from other oceans?
The Dead Sea is a salt lake bounded to the east by Jordan and to the west by Israel and the West Bank. It is located in the Jordan Rift Valley, and the Jordan River is its main tributary. The lake’s surface is 430.5 meters below sea level, making the lake’s shores the lowest land-based elevation on the planet. It is 304 meters deep, making it the world’s deepest hypersaline lake. It is one of the world’s saltiest bodies of water, with a salinity of 342 g/kg or 34.2 percent – 9.6 times saltier than the ocean – and density of dead sea water is 1.24 kg/liter, making swimming similar to floating. This salinity creates a harsh environment in which plants and animals cannot thrive, thus the name.
Evaporation can cause isolated bodies of water to become extra salty, or hypersaline in Dead Sea. Because of the high salt content, the water has a higher density, allowing people to float more easily in the Dead Sea than in the ocean.
Is sea water pure?
There is no such thing as pure sea water. Seawater is, in fact, water from a sea or ocean. The average salinity of seawater in the world’s oceans is about 3.5 percent. This means that each kilogram of seawater contains about 35 grams of dissolved salts. Because dissolved salts increase the mass more than the volume, seawater is denser than both fresh and pure water. As salt concentration increases in sea water, the freezing point of seawater decreases. It freezes at about -2 °C, at typical salinity.
Why sea is blue?
Because of the way light interacts with water, the sea frequently appears as blue. White light is composed of a variety of visible colors ranging from red to violet – red light has the longest wavelength, while blue light has the shortest. Water molecules absorb much of the red, orange, yellow, and green light because they are better at absorbing light with longer wavelengths. The shorter wavelengths of bluer colors are less likely to be absorbed, giving the sea its blue hues.
Because there are fewer water molecules to absorb light in shallow water, other colors can reach the sea floor and reflect. The deeper you go, the more other colors are absorbed and the light becomes deeper blue, until you reach a point where no visible light can reach and it is completely dark. The color of the water is also affected by other factors, such as the particles that float in it. Coastal areas can appear murky and brown at times because they contain sand from the seabed that has been churned up by waves.
The color is also influenced by living things. Phytoplankton are microscopic organisms that, like plants, absorb sunlight and grow by using chlorophyll. They absorb red and blue light while reflecting green light and making the sea appear greener. In general, the more phytoplankton there is in the water, the greener it appears. Phytoplankton are critical because they produce more than half of the world’s oxygen (every second breath you take comes from the sea!) and form the foundation of marine food webs.