This is an image of an estuary near San Diego, California.
Click on image for full size
Cation Exchange in Groundwater
Groundwater often contains dissolved minerals in the form of ions, such as dissolved calcium, or magnesium, which come from the weathering of surface rocks as well as dissolved organic compounds such as detritus, animal waste, or human contaminants.
As this water percolates through an aquifer, it may be modified and changed. Material comprising the aquifer may contain material which has a strong natural tendency to exchange one ion for another. In such an aquifer, calcium or magnesium in the water may be exchanged for sodium. For example, limestone, CaCO3, dissolves to become Ca+ and CO3-. The Ca+ may exchange with another chemical element such as Mg+, to form the rock MgCO3.
After awhile excess accumulation of one particular ion in the soil of the aquifer may force a chemical change in the rock which form the aquifer leading to metamorphism in that rock.
Eventually dissolved minerals are carried to the sea where these ions form salts. Thus sea water, the repository of dissolved material, especially carbonates, tends to be salty.
Shop Windows to the Universe Science Store!
The Spring 2010 issue of The Earth Scientist
, focuses on the ocean, including articles on polar research, coral reefs, ocean acidification, and climate. Includes a gorgeous full color poster!
You might also be interested in:
An aquifer is the name for a layer of rock which is capable of holding a large amount of water. Some layers are better at holding water than others, for example a layer of sandstone can hold a good deal...more
Carbonate is a name for rocks and minerals which contain a certain form of carbon/oxygen compound known as CO32-. (CO32- is also known as the molecule carbonate). Limestone is an example of a calcium carbonate,...more
The deep ocean waters are under pressure and are much colder than layers of the ocean which are closer to the surface. Dissolved carbon dioxide seems to be absent from the deep ocean water and as a result...more
One process which transfers water from the ground back to the atmosphere is evaporation. Evaporation is when water passes from a liquid phase to a gas phase. Rates of evaporation of water depend on factors...more
The water at the ocean surface is moved primarily by winds. Large scale winds move in specific directions because they are affected by Earth’s spin and the Coriolis Effect. Because Earth spins constantly,...more
Rivers are very important to Earth because they are major forces that shape the landscape. Also, they provide transportation and water for drinking, washing and farming. Rivers can flow on land or underground...more
About 70% of the Earth is covered with water, and we find 97% of that water in the oceans. Everyone who has taken in a mouthful of ocean water while swimming knows that the ocean is really salty. All water...more