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Geology Spices Avery Island

A Hot , Spicy Island

Deep down in the "heart of Cajun Country" near Vermilion Bay sit some historic and impressive geologic oddities -- five salt dome islands rising above the flat Louisiana Gulf Coast.

There are over 500 salt domes in the onshore and near offshore part of the northern Gulf Coast region, and others occur in Mexico, Central America, Cuba and under the GOM.

Not truly islands, these marvels are elevated mounds surrounded by Holocene coastal marshes.

The five Louisiana islands, arched up by rising salt stocks, are the only large topographic hills in the swamp, marsh and coastal plains of southern Louisiana -- and were a conscript habitation for prehistoric Indians and later European settlers.

Geologists believe these mysterious elevations were created when a saltwater ocean covering what is now Texas, Louisiana and Mississippi evaporated, leaving behind a vast sheet of salt.

The salt was formed in a narrow sea that existed during an early stage in the breakup of the supercontinent Pangea, more than 200 million years ago.

Over time this salt layer was covered by thousands of feet of alluvial sediment, the pressure of which pushed numerous salt domes straight up. In five places these domes actually pushed up the topography.

Today, these five coastal islands sit above and are surrounded by the drab, yet strangely exquisite swamps and marshes of south Louisiana.

The islands -- Avery, Weeks, Côte Blanche, Belle Isle and Jefferson -- are circular topographic prominences from one to two miles in diameter, rising 75 feet or more above the surrounding marshlands.

Avery Island stands the highest at 152 feet above sea level.

Image Caption

Avery Island's underground city of salt. Courtesy of Cargill Salt Division

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Deep down in the "heart of Cajun Country" near Vermilion Bay sit some historic and impressive geologic oddities -- five salt dome islands rising above the flat Louisiana Gulf Coast.

There are over 500 salt domes in the onshore and near offshore part of the northern Gulf Coast region, and others occur in Mexico, Central America, Cuba and under the GOM.

Not truly islands, these marvels are elevated mounds surrounded by Holocene coastal marshes.

The five Louisiana islands, arched up by rising salt stocks, are the only large topographic hills in the swamp, marsh and coastal plains of southern Louisiana -- and were a conscript habitation for prehistoric Indians and later European settlers.

Geologists believe these mysterious elevations were created when a saltwater ocean covering what is now Texas, Louisiana and Mississippi evaporated, leaving behind a vast sheet of salt.

The salt was formed in a narrow sea that existed during an early stage in the breakup of the supercontinent Pangea, more than 200 million years ago.

Over time this salt layer was covered by thousands of feet of alluvial sediment, the pressure of which pushed numerous salt domes straight up. In five places these domes actually pushed up the topography.

Today, these five coastal islands sit above and are surrounded by the drab, yet strangely exquisite swamps and marshes of south Louisiana.

The islands -- Avery, Weeks, Côte Blanche, Belle Isle and Jefferson -- are circular topographic prominences from one to two miles in diameter, rising 75 feet or more above the surrounding marshlands.

Avery Island stands the highest at 152 feet above sea level.

The islands are copiously vegetated and support a rich wildlife, including the Louisiana black bear and nutria imported from South America. Tropical gardens have been cultivated on Jefferson and Avery islands, and the latter is home to the world-famous Tabasco® sauce and also houses a rare-bird sanctuary and exotic tropical plants. Both islands are notable tourist attractions.

Please Pass the Salt

The history of Avery Island is as unique as the island itself.

A young boy in 1791 discovered a salty spring and began carrying the brine home. His family would boil the brine to recover the salt, as did many of our ancestors.

The first discovery of rock salt on our continent took place at Avery Island in 1862. In an attempt to expand his brine evaporating operation by depending on one of his salt springs, John Marsh Avery found the dome at an amazingly shallow depth of 16 feet.

The island quickly gained fame as an important strategic salt resource of the Confederacy during the Civil War.

Around 1867 to 1869, the first mine shaft was sunk through 58 feet of a solid salt dome to a depth of 90 feet.

Production was increased in 1880, when a railroad extension was built to the island, but water seepage caused abandonment of the mine in 1891.

In 1899, the International Salt Company gained control of all Avery Island salt operations and extended the main shaft to a depth of 550 feet. In 1973, a new shaft, 1,000 feet deep was completed.

Today, Avery Island is now an integral part of Cargill Salt, the largest and premier producer of rock salt in the world.

Weeks Island is the second highest of the Five Islands, and has the second oldest salt production operated by Morton Salt.

A Delicious Attraction

A visit to Avery Island will definitely clear your sinuses.

From pepper pods obtained shortly after the Civil War, Edmund McIlhenny cultivated a crop, founded a company and invented a world-famous product -- Tabasco® sauce.

Visit Avery Island today and you can see pepper plants being nurtured for next year's crop. Seeds are planted on the island and exported to Central and South America, where tabasco peppers are cultivated and harvested.

Each January, seeds of special capsicum peppers are planted in greenhouses; seedlings are transplanted to the fields in April, and by August the peppers reach just the right shade of red and are handpicked.

"The pepper pickers are given a petit bâton rouge (a little red stick) in order to match the color to perfection," said Dave Landry, visitor relations specialist with the McIlhenny Co.

Peppers are then mashed with Avery Island salt -- and then the mash is fermented and aged for three years in oak barrels. Finally, the aged mash is mixed with vinegar, stirred for a month, strained, and poured into bottles.

Visiting the Tabasco® sauce factory may make people with certain appetites feel a little like Augustus Gloop when he found himself delving into Mr. Wonka's chocolate river.

Oil Production?

It is an obvious assumption that oil and gas production be prominent on the Five Islands.

However, the production is privately owned and not discussed publicly.

Exxon reportedly has ongoing oil operations at Avery Island, and there are several very deep petroleum wells that penetrate for hundreds of meters through the salt overhang into the sediments below.

Petroleum wells on the west side of the island are drilled from barges in canals; those on the east from land rigs.

In November 1980, a Texaco well was drilled into or adjacent to a salt mine on Jefferson Island. The mine flooded, draining Lake Peigneur and causing a large collapse structure.

Most features are now under water, but an arcuate "bite" into the otherwise oval-shaped shore line and minor collapse features can be seen from the Live Oak Gardens on Jefferson Island.

Texaco operates the oil and gas field, which lies principally on the south side of Jefferson island.

Island Hopping

Those who are in southern Louisiana and have a chance to visit the islands are usually not disappointed.

The scenery and drive are beautiful -- and the unique subsurface geology makes the trip seem even more exotic.

The Tabasco® sauce factory is open to the public Monday through Sunday, 9 a.m.- 4 p.m. It is closed on major holidays. Admission is a 50-cent toll.

Jungle Gardens at Avery Island is open every day, including holidays, 8 a.m.-5 p.m. Admission is $5.75 for adults, $4 for children, plus the 50- cent toll to enter the island.

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