Another source of salts in the ocean is hydrothermal fluids, which come from vents in the seafloor. The heat causes a series of chemical reactions. The water tends to lose oxygen, magnesium, and sulfates, and pick up metals such as iron, zinc, and copper from surrounding rocks. The heated water is released through vents in the seafloor, carrying the metals with it. Some ocean salts come from underwater volcanic eruptions, which directly release minerals into the ocean.
Salt domes also contribute to the ocean's saltiness. This extremely high salinity is a result of the hot, arid conditions in the Middle East that lead to high rates of evaporation.
In addition, in the s the flow from the Jordan River was diverted away from the Dead Sea, so there is no longer significant fresh water input. With no input and high evaporation, the water level in the Dead Sea is receding at a rate of about 1 m per year. The high salinity makes the water very dense, which creates buoyant forces that allow people to easily float at the surface.
But the high salinity also means that the water is too salty for most living organisms, so only microbes are able to call it home; hence the name the Dead Sea. But as salty as the Dead Sea may be, it is not the saltiest body of water on Earth.
While local conditions are important for determining salinity patterns in any single location, there are some global patterns that bear further investigation. Temperature is highest at the equator, and lowest near the poles, so we would expect higher rates of evaporation, and therefore higher salinity, in equatorial regions Figure 5.
This is generally the case, but in the figure below salinity right along the equator seems to be a little lower than at slightly higher latitudes. This is because equatorial regions also get a high volume of rain on a regular basis, which dilutes the surface water along the equator. So the higher salinities are found at subtropical, warm latitudes with high evaporation and less precipitation.
At the poles there is little evaporation, which, coupled with ice and snow melting, produces a relatively low surface salinity. The image below shows high salinity in the Mediterranean Sea; this is located in a warm region with high evaporation, and the sea is largely isolated from mixing with the rest of the North Atlantic water, leading to high salinity. Lower salinities, such as those around southeast Asia, are the result of precipitation and high volumes of river input. Figure 5.
Green colors represent areas where precipitation exceeds evaporation, while brown regions are where evaporation is greater than precipitations. Note the correlation between precipitation, evaporation, and surface salinity as seen in Figure 5.
In addition to geographical variation in salinity, there are also changes in salinity with depth. As we have seen, most differences in salinity are due to variations in evaporation, precipitation, runoff, and ice cover.
All of these process occur at the ocean surface, not at depth, so the most pronounced differences in salinity should be found in surface waters. Salinity in deeper water remains relatively uniform, as it is unaffected by these surface processes.
However, the effect is greater if the salty water gets cold, as temperature has a greater effect on density than salinity does. A combination of high salinity and low temperature makes seawater so dense that it sinks to the bottom of the ocean and flows across ocean basins as deep, slow currents.
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Email Us. See our newsletters here. These images attempt to show three dimensions, so each sphere represents "volume. Salt is also used as feedstock for chlorine and caustic soda manufacture; these two inorganic chemicals are used to make many consumer-related end-use products, such as. This photo shows a road salt storage stockpile that is awaiting use for pavement deicing, Port of Milwaukee, WI. The use of salt to deice pavement can be harmful to aquatic life in urban streams.
The USGS is involved in studies that focus on the influence of winter runoff on aquatic ecosystems. Why is the ocean salty? Rivers discharge mineral-rich water to the oceans is from outflow from rivers, which drain the landscape, thus causing the oceans to be salty.
Skip to main content. Search Search. Here's how it works: From precipitation to the land to the rivers to the sea Apply Filter. Where can I find bathymetric data? The USGS has made bathymetric surveys for many coastal areas and for selected rivers and lakes in the U.
What is marine geology? Geology is the study of the Earth. This includes how the Earth was formed, how the Earth has changed since it was formed, the materials that make up the Earth, and the processes that act on it. Marine Geology focuses on areas affected by our oceans including the deep ocean floor, the shallower slopes and shelves that surround the continents, and Where can I get current sea-surface temperature data?
What is the difference between a tsunami and a tidal wave? Although both are sea waves, a tsunami and a tidal wave are two different and unrelated phenomena. A tidal wave is a shallow water wave caused by the gravitational interactions between the Sun, Moon, and Earth "tidal wave" was used in earlier times to describe what we now call a tsunami.
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