Where does the salt come from?
What is the difference between land and sea salt?Salt that is found on the land can come from evaporated ancient oceans, for instance, in the south of Spain today, there are large deposits of gypsum and salt that formed during a period of time known as the Messinian Salinity Crisis. During this period, several kilometres of seawater evaporated from cut-off basins, and left behind a series of minerals, including halite (rock salt) in thick layers. This salt would have been in similar concentrations to the salt in the ocean today.However, there are other sources of salt on the land. The photographs of volcanoes on this site are incredible. It is run by a team of volcanologists who travel the world and photograph volcanic activity. In Dallol, there are vast salt lakes that are formed in a completely different way. Here, the groundwater is heated from below, as the plates are pulling apart in the region, and the magma is close to the surface, hence the series of Great Lakes and volcanoes throughout the Rift Valley.When this water is heated, it dissolves a wide range of minerals in the pore waters, and brings them up to the surface. When they reach the surface they cool, and the salt in the waters returns to its crystalline form. Because this salty water is effectively “erupted” at high temperatures, it forms a variety of unusual, and often very short-lived geological features, such as the “hornitoes” seen in some of these photos. The end result is a region very rich in salt, which has been mined for several centuries. The colours in the photographs come from a range of accessory minerals that are also dissolved by the hot waters.
Exploring Our Ocean
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