Tree Rings Solve Mystery of World Trade Center Ship
Lower Manhattan Development Corporation, via Columbia University
Four years after a shipwreck was revealed at Ground Zero, a new report details how tree rings helped establish the origins of the wooden vessel.
Sept. 12, 2011 --
In the search for buried history, archaeologists pour their resources into uncovering the remnants of the distant past. With know-how, persistence and a little luck, archaeologists can push aside dirt and rock and find an artifact of historical significance. Although chance plays a big role in unearthing history, archaeological treasures have been stumbled upon purely by accident, often by those outside the scientific community. In these photos, explore several particularly serendipitous finds of unique artifacts, some of which reach as far back as prehistory.
On Sept. 12, 1940, four teenagers followed their wayward dog into a cave complex near the village of Montignac in southwestern France. To their surprise, the caves hosted something remarkable: nearly 2,000 paintings and etchings of animals, humans and abstract shapes on the walls dating back between 15,000 and 25,000 years. Known as the Lascaux caves, the complex features figures depicted in surprising detail given the age of the illustrations. Animals portrayed on the cave walls included horses, stags, bison and felines. Archaeologists believed the caves were used for ritualistic purposes. Some parts of the illustrations even appear to construct a narrative, but what they mean exactly has yet to be deciphered. The caves were open to the public in 1948, but closed in 1963 in order to preserve the site from damage.
The Dead Sea Scrolls are a collection of over 800 biblical texts made of animal skin and papyrus. Dating to around 2,000 years ago, between the years 200 B.C. and 70 A.D., the scrolls could well be the oldest such documents in existence and have deepened historians' understanding of religious history. These documents may have been lost to history had a Bedouin shepherd named Muhammed edh-Dhib and his cousin not stumbled upon the first manuscripts along the northern shore of the Dead Sea at a remote site known as Qumran in 1947. The last fragments of the Dead Sea Scrolls collection was uncovered in the mid-1950s. Although the scrolls have been extensively studied and translated, one big mystery remains: Who exactly wrote them?
As Napoleon Bonaparte's army marched through north Africa during his campaign in Egypt, they stumbled upon what would become known as the Rosetta Stone, after the town where it was discovered. Within Bonaparte's army was a squadron of scholars called Institute of Egypt, also known as the Scientific and Artistic Commission. As the military settled around the Nile Delta, the Institute explored local ruins and artifacts. After the discovery of the stone in 1799, several copies of the inscriptions on its face were made, since no one could read them at the time. By 1802, the Greek and Demotic portions of the stone had been deciphered by scholars. The hieroglyphics posed a different challenge all together, however, and it would take 20 years before French scholar Jean-François Champollion announced that he had cracked the code. By deciphering the hieroglyphs, Champollion opened a whole new door to understanding the civilization of ancient Egypt. The Rosetta Stone is currently kept in the British Museum.
In case you don't know what a geoglyph is, ancient Peruvians went through the trouble of leaving a picture-perfect definition. Known as the Nazca Lines, these giant carvings into the Earth were only discovered by airplane in the 1930s. Located in the Nazva desert in southern Peru around 250 miles (400 kilometers) south of Lima, the geoglyphs resemble a number of animals including a spider (as seen here), a condor, a monkey, a tree, as well as human figures and geometric patterns. Why exactly indigenous tribes living in the area between 100 B.C. and 650 A.D. felt compelled to produce these works remains a mystery, though archaeologists agree that it is likely tied to religious customs.
In 1991, German tourists stumbled upon a frozen body in a glacier on the Ötztal Alps between Italy and Austria. Although they originally thought the corpse to be the result of a recent death, the iceman mummy, named Ötzi, in fact dated back 5,300 years. Since Ötzi's discovery, the mummy has been extensively studied. Scientists have learned everything from his last meal to his cause of death to his possible occupation and they have even made reconstructions of his face. Ötzi died in the spring as a result of an arrowhead striking his left clavicle artery. He likely received a ceremonial burial and was found beside tools and other personal items.
Over the years, metal detector enthusiasts, particularly those in the United Kingdom, have uncovered archaeological treasures buried beneath the Earth. In 2009, 30-year-old Nick Davies hauled in 10,000 ancient Roman coins that he had found inside a clay pot buried in Shropshire, U.K. That same year, a trove of 1,500 gold and silver pieces dating back to the Dark Ages were found on a farmer's field in the western region of Staffordshire, England. Last year, 63-year-old David Crisp uncovered 52,000 ancient Roman coins, later given a value of around $1 million, in a clay pot in southwestern England.
Ministero per i Beni e le Attivita Culturali,
In 1986, divers stumbled upon a nearly 2,000-year-old Roman shipwreck some six miles off the coast of the town of Grado, Italy. Measuring 55 feet long and 16 feet wide, the small trade vessel was stocked with 600 amphorae, or vases, packed with sardines and other fish. Further study of the shipwreck revealed that the ancient Roman engineers also had built in a hydraulic system that allowed the ship to carry an aquarium with live fish.
In July 2010, amid the gargantuan rebuilding effort at the site of the World Trade Center in Lower Manhattan, construction workers halted the backhoes when they uncovered something unexpected just south of where the Twin Towers once stood.
At 22 feet (6.7 meters) below today's street level, in a pit that would become an underground security and parking complex, excavators found the mangled skeleton of a long-forgotten wooden ship.
Now, a new report finds that tree rings in those waterlogged ribs show the vessel was likely built in 1773, or soon after, in a small shipyard near Philadelphia. What's more, the ship was perhaps made from the same kind of white oak trees used to build parts of Independence Hall, where the Declaration of Independence and U.S. Constitution were signed, according to the study published this month in the journal Tree-Ring Research. [See Photos of the Ship and Its Tree Rings]
Archaeologists had been on-site throughout the excavation of the World Trade Center's Vehicular Security Center. They had found animal bones, ceramic dishes, bottles and dozens of shoes, but the excitement really kicked up when the 32-foot-long (9.75 m) partial hull of the ship emerged from the dirt.
The vessel was quickly excavated, to prevent damage from exposure to the air. Piece by piece, the delicate oak fragments were documented and taken out of the rotten-smelling mud. The timbers were sent to the Maryland Archaeological Conservation Laboratory, where they would be soaked in water to keep the wood from cracking and warping.
A few timbers were sent back to New York, just 20 miles (32 kilometers) north of the World Trade Center, to the Tree Ring Laboratory at Columbia University's Lamont-Doherty Earth Observatory in Palisades, New York. Researchers at the lab dried the fragments slowly in a cold room and cut thick slices of the wood to get a clear look at the tree rings.
The team established that the trees used to build the ship — some of which had lived to be more than 100 years old — were mostly cut down around 1773. Then, to determine where the wood came from, the researchers had to find a match between the ring pattern in the timbers and a ring pattern in live trees and archaeological samples from a specific region.
Rings in the white oak timbers used to build the ship reveal that the vessel was built around 1773 near Philadelphia.Lower Manhattan Development Corporation, via Columbia University
"What makes the tree-ring patterns in a certain region look very similar, in general, is climate," said the leader of the new study, Dario Martin-Benito, who is now a postdoctoral fellow at the Swiss Federal Institute of Technology (ETH) in Zurich. Regional ring patterns arise from local rain levels and temperatures, with wetter periods producing thicker rings and drier periods producing smaller rings, he said.
Martin-Benito and his colleagues at Columbia's Tree Ring Lab narrowed their search to trees in the eastern United States, thanks to the keel of the ship, which contained hickory, a tree found only in eastern North America and eastern Asia. Otherwise, the researchers would have had much more difficulty in limiting their search, as oak is found all over the world. [Shipwrecks Gallery: Secrets of the Deep]
The ship's signature pattern most closely matched with the rings found in old living trees and historic wood samples from the Philadelphia area, including a sample taken during an earlier study from Independence Hall, which was built between 1732 and 1756.
"We could see that at that time in Philadelphia, there were still a lot of old-growth forests, and [they were] being logged for shipbuilding and building Independence Hall," Martin-Benito told Live Science. "Philadelphia was one of the most — if not the most — important shipbuilding cities in the U.S. at the time. And they had plenty of wood so it made lots of sense that the wood could come from there."
Historians still aren't certain whether the ship sank accidently or if it was purposely submerged to become part of a landfill used to bulk up Lower Manhattan's coastline. Oysters found fixed to the ship's hull suggest it at least languished in the water for some time before being buried by layers of trash and dirt.
Previous investigations found that the vessel's timbers had been damaged by burrowing holes of Lyrodus pedicellatus, a type of "shipworm" typically found in high-salinity, warm waters — a sign that the ship, at some point in its life, made a trip to the Caribbean, perhaps on a trading voyage. Martin-Benito speculated that the infestation might have been one of the reasons the ship met its demise just 20 or 30 years after it was built.
"I don't know much about the life expectancy for boats, but that doesn't seem like too long for something that would take so long to build," Martin-Benito said.
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In Photos: Mission to 2,000-Year-Old Antikythera Shipwreck
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The 7 Most Mysterious Archaeological Finds on Earth