“黒ひげ”の沈没船 砂で完全に密閉

(いろいろな意味で)有名な海賊の発掘が進んでいます。Queen Anne’s Revenge号は１７１８年にイギリスに軍の攻撃を受け沈みました。１９９６年にノースキャロライナ州沖で発見され、２０００年から一部発掘調査が進められています。水中に放置しておくと有機物は少しずつ分解して行きます。また、金属遺物も有機物ほどではないものの、被害を受けます。これらの遺物を引き上げた際には保存処理が必要です。今回の調査は遺物の一部引き上げと水中サイトマップの作成が行われ、大きな遺物などは水中で保存されます。

その保存方法は、砂で完全に遺跡を埋めて密閉しようというものです。砂に埋もれれば海水中の酸素から遮断され、バクテリアなど遺物を分解する要因がなくなります。約２ｍの砂に埋める予定だそうです。突発的な地形の変化が水底にあると、そこだけ波の影響を受けやすくなるため遺跡の場所だけ砂でかぶせても波の影響などで直ぐに砂が移動してしまいます。そこで、緩やかなスロープを作り水底の地形が無理なく変化するよう作業が進められる予定です。約２００ｍｘ７０ｍのエリアが砂でかぶされるそうです。

Blackbeard’s Presumed Ship Gets New Layer

By STEVE HARTSOE Associated Press Writer
© 2006 The Associated Press

RALEIGH, N.C. — Authorities are resorting to a risky new method aimed at helping preserve what is believed to be the sunken flagship of the pirate Blackbeard.

The Army Corps of Engineers is creating an underwater sand dune to shelter the Queen Anne’s Revenge, which sits about 26 feet underwater off the North Carolina coast.

The untried method could potentially damage the ship, which sank in 1718. But if it works, experts said it could be a model for protecting other underwater archaeological finds.

“We don’t really know what it’s going to do,” said Bill Adams, a biologist with the Corps.

The idea of burying the wreck in sand was suggested in the state’s plan for managing the site after it was discovered in 1996.

Project archaeologist Chris Southerly said the burial was made possible because the corps was dredging near the site and had a ready supply of sand. Dredging began Wednesday.

The dumped sand will create a slope on the ocean floor that’s about 600 feet long, 200 feet wide and 6 feet tall. Experts hope ocean currents will carry sand toward the ship, replenishing the protective covering it once had.

Archeologists have been retrieving artifacts from the wreck for years and haven’t stopped diving on the site. But exposure of cannons, anchors, and other artifacts is now at a “critical point,” Southerly said.

Organic material like wood are especially at risk of rapid deterioration with the loss of the preserving cover of sand, he said.

Blackbeard, whose real name was widely believed to be Edward Teach or Thatch, was tracked down at Ocracoke Inlet by volunteers from the Royal Navy and killed in a battle on Nov. 22, 1718.

Some scientists, including a pair of professors who published an article last year, have questioned whether the wreck is the Queen Anne’s Revenge. They suggest the vessel is more likely a mid-18th century merchant ship than a pirate’s boat.

But Southerly, who’s been studying the Queen Anne’s Revenge since 2000, said research supports his view that the ship, discovered in 1996, belonged to Blackbeard.

“The Queen Anne’s Revenge is the only candidate that fits, that is documented in Beaufort Inlet,” he said.

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On the Net:

Queen Anne’s Revenge Shipwreck Project: http://www.qaronline.org

引用元：http://www.chron.com/disp/story.mpl/ap/science/3678811.html