Karst aquifers
In the United States, about 40% of the groundwater used for drinking comes from karst aquifers. Some of these areas are well known vacation destinations like Carlsbad Caverns and Mammoth Cave. Karst aquifers are a vital resource in the US; about 20 percent of the land surface in the US is classified as karst. Other parts of the world with large areas of karst include the Caribbean, China, and Australia. Typical karst hydrogeology consists of a network of interconnected fissures, fractures, and conduits emplaced within permeable rock. Most of the groundwater flow occurs through a network of openings, while groundwater is held in storage within the geological structures themselves. List of karst aquifers in North America
Arbuckle-Simpson aquifer
Basin and Range and Bear River range carbonate aquifers
Colorado Plateau karst
Edwards Balcones Fault Zone aquifer
Edwards-Trinity Plateau aquifer
Upper Floridan and Biscayne aquifers
Madison aquifer
Midwest Paleozoic Carbonate aquifers
New England karst aquifers
Ozark Plateau karst aquifers
Roswell Basin aquifer
Pacific Northwest basalt aquifers
Valley and Ridge, Piedmont, and Blue Ridge aquifers

See also
Fabric (geology)
Fissure vein
Thermokarst
Topography

References
External links
External images of Almannagja fissures
In the human body it is first converted to phenylbutyryl-CoA and then metabolized by mitochondrial beta-oxidation, mainly in the liver and kidneys, to the active form, phenylacetate. Phenylacetate conjugates with glutamine to phenylacetylglutamine, which is eliminated with the urine. It contains the same amount of nitrogen as urea, which makes it an alternative to urea for excreting nitrogen.A 5g tablet or powder of sodium phenylbutyrate taken by mouth can be detected in the blood within 15 minutes, and reaches peak concentration in the bloodstream within an hour. It is metabolized into phenylacetate within half an hour. See also
Glycerol phenylbutyrate

References
External links
"Sodium phenylbutyrate". Drug Information Portal. U.S. National Library of Medicine.