ThalwegIn geography and fluvial geomorphology, a thalweg or talweg (ˈtɑːlvɛɡ) is the line of lowest elevation within a valley or watercourse. Under international law, a thalweg is taken to be the middle of the primary navigable channel of a waterway that defines the boundary line between entities such as states. Thalwegs can acquire special significance because disputed river borders are often deemed to run along the river's thalweg. The word thalweg is of 19th-century German origin.
Groundwater remediationGroundwater remediation is the process that is used to treat polluted groundwater by removing the pollutants or converting them into harmless products. Groundwater is water present below the ground surface that saturates the pore space in the subsurface. Globally, between 25 per cent and 40 per cent of the world's drinking water is drawn from boreholes and dug wells. Groundwater is also used by farmers to irrigate crops and by industries to produce everyday goods.
Tidal lockingTidal locking between a pair of co-orbiting astronomical bodies occurs when one of the objects reaches a state where there is no longer any net change in its rotation rate over the course of a complete orbit. In the case where a tidally locked body possesses synchronous rotation, the object takes just as long to rotate around its own axis as it does to revolve around its partner. For example, the same side of the Moon always faces the Earth, although there is some variability because the Moon's orbit is not perfectly circular.
Sea foamSea foam, ocean foam, beach foam, or spume is a type of foam created by the agitation of seawater, particularly when it contains higher concentrations of dissolved organic matter (including proteins, lignins, and lipids) derived from sources such as the offshore breakdown of algal blooms. These compounds can act as surfactants or foaming agents. As the seawater is churned by breaking waves in the surf zone adjacent to the shore, the surfactants under these turbulent conditions trap air, forming persistent bubbles that stick to each other through surface tension.
History of saltSalt, also referred to as table salt or by its chemical formula NaCl (sodium chloride), is an ionic compound made of sodium and chloride ions. All life depends on its chemical properties to survive. It has been used by humans for thousands of years, from food preservation to seasoning. Salt's ability to preserve food was a founding contributor to the development of civilization. It helped eliminate dependence on seasonal availability of food, and made it possible to transport food over large distances.
Wieliczka Salt MineThe Wieliczka Salt Mine (Kopalnia soli Wieliczka) is a salt mine in the town of Wieliczka, near Kraków in southern Poland. From Neolithic times, sodium chloride (table salt) was produced there from the upwelling brine. The Wieliczka salt mine, excavated from the 13th century, produced table salt continuously until 2007, as one of the world's oldest operating salt mines. Throughout its history, the royal salt mine was operated by the Żupy Krakowskie (Kraków Salt Mines) company.
