section_path: Geology/Brine pools
section_name: Brine pools
paragraph_text: Brine pools
  
  A number of brine pools, sometimes called brine lakes, are known on the seafloor of the northern half of the Gulf of Mexico. Brine pools in the Gulf of Mexico range from just 1 metre (3 ft 3 in) across to 20 kilometres (12 mi) long. Brine is produced wherever the water of the Gulf comes in contact with the Louann Salt, a evaporite formation from the Jurassic period, along faults or in unconsolidated sediments. The Louann Salt extends under most of the continental shelf around the northern part of the Gulf from west of Florida to Texas. Under the pressure of overlaying sediments, the salt deforms and migrates, a process known as salt tectonics. Masses of salt may rise through overlaying sediments to form salt domes, or may be extruded along the Sigsbee Escarpment where the slope of the continental shelf exposes lower laying stata.
  
  The brines usually exceed 200 parts-per-thousand (ppt) of salt and are 25% or more denser than most seawater (average 35 ppt). The density difference inhibits mixing of the brine with other sea water, and the brine flows downslope and gathers in depressions in the gulf floor. Hydrocarbons and gas hydrates rising from salt diapirs may cause doming of the gulf floor, with the gas sometimes erupting strongly enough to leave a depression in the gulf floor surrounded by a rim, where brine may pool. The East Flower Garden Bank brine pool is in a crater formed by the collapsed cap of a salt dome. The circular pool covers 500 square metres (5,400 sq ft) with a maximum depth of 25 centimetres (9.8 in), and is 70 metres (230 ft) beneath the surface of the Gulf. It is anoxic and contain quantities of hydrogen sulfide and methane.: 383
  
  The brine pool known as GB425, which is 600 metres (2,000 ft) deep, is fed by a mud volcano. The temperature at the surface of the pool can vary from 6 to 48 °C (43 to 118 °F), and is on average 20 °C (68 °F) warmer than normal bottom temperatures. The brine pool known as GC233 is at a depth similar to that of GB425, 650 metres (2,130 ft) deep. The pool sits in a depression at the top of a mound and covers about 190 square metres (2,000 sq ft). While GC233 has a lower inflow of brine than GB425 and a temperature about 15 °C (59 °F) below that of GB425, the two pools share some similarities, such as a salinity of about 130 ppt, low sulfides, almost no sulfates, and high concentrations of hydrocarbons.
  
  The Orca Basin is 2,100 metres (6,900 ft) deep, and covers about 400 square kilometres (150 sq mi) with a maximum depth of 350 metres (1,150 ft). The large size is the result of the merger of several salt domes. Salinity in the pool increases gradually over a depth of 75 metres (246 ft), and reaches 300 ppt at depth, with zero dissolved oxygen.: 383–384
  
  A brine pool was discovered in 2014 on the sea floor at a depth of 3,300 feet (1,000 m) with a circumference of 100 feet (30 m) and depth of 12 feet (4 m), which is four to five times saltier than the surrounding water. The site cannot sustain any kind of life other than bacteria, mussels with a symbiotic relationship, tube worms, and certain kinds of shrimp. It has been called the "Jacuzzi of Despair" because it is warmer at 18 °C (65 °F) compared to the surrounding water at 4 °C (39 °F).
  
  A number of brine pools, sometimes called brine lakes, are known on the seafloor of the northern half of the Gulf of Mexico. Brine pools in the Gulf of Mexico range from just 1 metre (3 ft 3 in) across to 20 kilometres (12 mi) long. Brine is produced wherever the water of the Gulf comes in contact with the Louann Salt, a evaporite formation from the Jurassic period, along faults or in unconsolidated sediments. The Louann Salt extends under most of the continental shelf around the northern part of the Gulf from west of Florida to Texas. Under the pressure of overlaying sediments, the salt deforms and migrates, a process known as salt tectonics. Masses of salt may rise through overlaying sediments to form salt domes, or may be extruded along the Sigsbee Escarpment where the slope of the continental shelf exposes lower laying stata.
  
  The brines usually exceed 200 parts-per-thousand (ppt) of salt and are 25% or more denser than most seawater (average 35 ppt). The density difference inhibits mixing of the brine with other sea water, and the brine flows downslope and gathers in depressions in the gulf floor. Hydrocarbons and gas hydrates rising from salt diapirs may cause doming of the gulf floor, with the gas sometimes erupting strongly enough to leave a depression in the gulf floor surrounded by a rim, where brine may pool. The East Flower Garden Bank brine pool is in a crater formed by the collapsed cap of a salt dome. The circular pool covers 500 square metres (5,400 sq ft) with a maximum depth of 25 centimetres (9.8 in), and is 70 metres (230 ft) beneath the surface of the Gulf. It is anoxic and contain quantities of hydrogen sulfide and methane.: 383
  
  The brine pool known as GB425, which is 600 metres (2,000 ft) deep, is fed by a mud volcano. The temperature at the surface of the pool can vary from 6 to 48 °C (43 to 118 °F), and is on average 20 °C (68 °F) warmer than normal bottom temperatures. The brine pool known as GC233 is at a depth similar to that of GB425, 650 metres (2,130 ft) deep. The pool sits in a depression at the top of a mound and covers about 190 square metres (2,000 sq ft). While GC233 has a lower inflow of brine than GB425 and a temperature about 15 °C (59 °F) below that of GB425, the two pools share some similarities, such as a salinity of about 130 ppt, low sulfides, almost no sulfates, and high concentrations of hydrocarbons.
  
  The Orca Basin is 2,100 metres (6,900 ft) deep, and covers about 400 square kilometres (150 sq mi) with a maximum depth of 350 metres (1,150 ft). The large size is the result of the merger of several salt domes. Salinity in the pool increases gradually over a depth of 75 metres (246 ft), and reaches 300 ppt at depth, with zero dissolved oxygen.: 383–384
  
  A brine pool was discovered in 2014 on the sea floor at a depth of 3,300 feet (1,000 m) with a circumference of 100 feet (30 m) and depth of 12 feet (4 m), which is four to five times saltier than the surrounding water. The site cannot sustain any kind of life other than bacteria, mussels with a symbiotic relationship, tube worms, and certain kinds of shrimp. It has been called the "Jacuzzi of Despair" because it is warmer at 18 °C (65 °F) compared to the surrounding water at 4 °C (39 °F).