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How underwater archaeology reveals hidden wonders

This Maya skull was found by underwater archaeologists in a sacred cenote, or natural sinkhole, in Mexico.
Photograph by Paul Nicklen, Nat Geo Image Collection

From National Geographic by Erin Blakemore

Curious about still-hidden archaeological treasures?
Just add water—that’s the concept behind the emerging field of underwater archaeology.
But don’t be deceived: It’s anything but simple, and recent advances have made it one of the most exciting forms of modern archaeological research.

It’s always been difficult to access sites under water, but there’s a particular allure to potential archaeological sites hidden under oceans, lakes, and rivers.
Shipwrecks are far from the only thing to document, study, and preserve underwater: there’s also everything from very ancient human remains to submerged settlements, like portions of ancient Alexandria, the Egyptian city that partially sank into the Mediterranean over the centuries.

Over the years, the relatively recent discipline of underwater archaeology (which really got going with the use of scuba in the mid-20th century) has branched off into a number of subdisciplines that look at everything from how humans interact with water to the search for airplanes that make water their final resting place.
And plenty of above-ground archaeologists eventually find themselves looking to nearby bodies of water for answers.

Finding an ancient Spanish shipwreck
Led by clues found in old documents, maritime archaeologist Robert Grenier makes a thrilling discovery.

Challenging discipline

Often, the hunt for underwater objects presents serious logistical and interpretive questions.
It can be expensive to look underwater at all, and researchers must recruit divers (who are often also archaeologists) with the ability to document and handle delicate objects appropriately.
Weather conditions and tides can stymie an expedition.

And once a site is located, it can be tricky to study.
Water is dynamic, and objects are susceptible to its ebb and flow.
It can break up materials and jumble them in a way that makes interpretation difficult.
Conservation can be even trickier; water can be hard on already delicate objects, and moving a newly recovered object is even harder when it’s underwater.

This illustration shows a remotely operated submersible used in underwater research.

Illustration by Richard Schlecht, Nat Geo Image collection

Luckily, archaeologists have plenty of technology to combat those challenges.
LiDAR can reveal structures and objects underwater and map sites; sonar, magnetometors, and other remote sensing devices can help, too.
Advanced photography and videography can bring sites to life even for those who’ll never venture into the water.
And a new generation of submersibles is driving new discoveries.
The R/V Petrel, for example, carries two onboard robots that have helped uncover 21 World War II vessels, including the U.S.S. Indianapolis.

Helping hands

Underwater archaeology also depends on good relationships with other communities familiar with the bodies of water they work in.
That became clear to researchers who were alerted to a large cache of shipwrecks near Fourni, Greece, by a local fisher.
The assistance of the area’s fishers ended up helping archaeologists discover 23 shipwrecks in the area in 22 days.
Volunteers can drive much of the field, as in Florida, where volunteers work alongside archaeologists.

Octavio del Rio examines a skull from a funerary deposit in northern Yucatan, Mexico.

Photograph by Wes C. Skiles, Nat Geo Image collection

Local and international laws also apply: UNESCO, the UN’s cultural arm, has established international law around underwater cultural heritage that mandates in situ (“in place”) preservation as the ideal option when researching a submerged archaeological site.
That means many underwater finds must be left where they were found.

This can add another layer of challenge for researchers who document sites with locations that may never be revealed to the public in order to prevent vandalism or looting.
Other sites do find public lives, as did Baiae, a Roman seaside resort that is now an underwater museum open to visitors.

Working under the waves is challenging, but it can offer rich rewards for those seeking to understand the past.

Links :

• National Geographic : See how archaeologists discovered a long-lost slave ship / Last American slave ship is discovered in Alabama

How pioneering geologist Marie Tharp changed our view of Earth

Oceanic cartographer Marie Tharp helped prove the theory of continental drift with her detailed maps of the ocean floor.

This animation by Rosanna Wan for the Royal Institution tells the fascinating story of Tharp’s groundbreaking work.

From Forbes by David Bressan

Marie Tharp was born on July 30, 1920, in the city of Ypsilanti, Michigan.
As a young girl she followed her father, a soil surveyor for the United States Department of Agriculture, into the field.
She also loved to read and wanted to study literature at St.
John's College in Annapolis, but women were not allowed to join the courses.
So she went to Ohio University, where she graduated in 1943.

Marie Tharp used hundreds of seismic profiles to reconstruct the topography of the seafloor, like here of the Atlantic Ocean.

Lamont-Doherty Earth Observatory, Marie Tharp

She worked for a short time in the petroleum industry, but found the work unrewarding and decided to resume her studies at Tulsa University, Oklahoma.
In 1948 she graduated in mathematics and found a job at the Lamont Geological Laboratory at Columbia University.

At the time the U.S. Navy was interested in mapping the seafloor, believed to be of strategic importance for future submarine warfare.
Marie started a prolific collaboration with geologist Bruce Charles Heezen, a specialist for seismic and topographic data obtained from the seafloor.
As a woman, Marie was not allowed to get on board the research ships.
Instead, she interpreted and visualized the collected data in her laboratory, producing large hand-drawn maps of the seafloor.
By interpolating and plotting the echo soundings of the seafloor collected from the research ship in 1957 Marie Tharp noted the strange bathymetry of valleys and ridges of the mid-Atlantic ridge.
The existence of a ridge under the Atlantic Ocean was discovered during the expedition of HMS Challenger in 1872, taking depth measurements across the ocean.
In 1925 it was confirmed by sonar that the ridge of unknown origin extends around the Cape of Good Hope into the Indian Ocean, making it one of the most extended mountain range on Earth.
Marie Tharp suggested that the mid-ocean ridges had "rift valleys" running along their axes where new crust is formed, pushing apart blocks of older crust, forming the ridges.
Her idea dismissed at the time as "girl talk" by one of the expedition's leaders.

Original sketch by Tharp of the seafloor in the Mid-Atlantic.

Between 1959 and 1977 she continued to work on various large-scale maps that would depict the still mostly unknown bathymetry of the seafloor.

Not too many people can say this about their lives: The whole world was spread out before me (or at least, the 70 percent of it covered by oceans).
I had a blank canvas to fill with extraordinary possibilities, a fascinating jigsaw puzzle to piece together: mapping the world’s vast hidden seafloor.
It was a once-in-a-lifetime—a once-in-the-history-of-the-world—opportunity for anyone, but especially for a woman in the 1940s.
The nature of the times, the state of the science, and events large and small, logical and illogical, combined to make it all happen.

This animation portrays the motion of continents (grey, yellow, orange and red) and oceanic plates (blue) since Pangea breakup from 200 million years ago.

The model is a modified version of the Seton et al. (2012) plate reconstruction, and is used to analyse factors affecting plate velocities in Zahirovic et al. (2015).

The results indicate that continental keels slow down plate velocities, where Archean cratons (red) have the strongest effect in limiting plate speeds.
cortesy of EathByte, University of Sydney

The seafloor was not a series of muddy plains, as previously imagined by most geologists, but instead featured mountains, ridges and canyons, sometimes larger and deeper as any example found on the continents.
Along the mid-ocean rifts, molten rock rises up from Earth's mantle, pushing and pulling apart the oceanic crust.
This mechanism is not limited to the oceans but also involves the continents and is the driving force behind plate tectonics.

Links :

• GeoGarage blog : Marie Tharp: the woman who mapped the ocean floor / If the ocean was transparent : the see-through sea / How one brilliant woman mapped the ocean floor's ... / The floor of the ocean comes into better focus / Floor of the World Ocean, Harrison 1961 vs Garcia ... / The great challenge of mapping the sea / Secretly mapping the sea floor / Why the first complete map of the ocean floor is .. / The quest to map the mysteries of the ocean floor

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Fogo Island, Newfoundland Nautical Chart (1792)

Inside the search for Amelia Earhart’s airplane

Photograph by Gabriel Scarlett, National Geographic
Best known for his 1985 discovery of the Titanic, National Geographic Explorer Robert Ballard studies video monitors inside the control room of the research vessel E/V Nautilus.
Robert Ballard is on a mission to find out what happened to Amelia Earhart when she disappeared during her quest to be the first woman to fly around the world 

From MSN by Rachel Hartigan Shea

It’s a balmy tropical night south of the equator in the Pacific Ocean, but inside the control room of the E/V Nautilus it’s cold and dark and hushed.
Banks of monitors provide the only light.
Moving around is treacherous—wires hang along the walls and the space between work stations is narrow.
Despite the heat outside, crew members wear fleece to fend off the frigid air.
Their voices are barely audible as they speak softly to each other through headsets.

© Alamy Stock Photo
Amelia Earhart strides in front of her Lockheed Electra, the plane in which she disappeared in July 1937 while attempting to become the first woman to fly around the world.

The screens mounted on the black-painted walls provide a vision of another world.
One shows a remotely operated vehicle (ROV) floating in shadowy blue light, dwarfed by what looks to be a massive cliff face.
Another screen provides a closer view—bedrock and coral rubble occasionally obscured by a flurry of marine snow.

“We’re looking for colors that aren’t natural to the background,” says Robert Ballard, as he stares intently at the screens from his perch in the back row.
The man who found the Titanic is on a mission to find out what happened to Amelia Earhart when she disappeared during her quest to be the first woman to fly around the world.

Earhart would likely have been enraptured by the ship’s space-age display.
The aviator always had her eye on the future, whether it was records to be broken in the skies or new paths to be forged by women.
She even ventured underwater in an early version of a diving suit.

Yet she would have been astonished at the technological wonders being marshaled to discover her fate.

Ballard has directed his state-of-the-art ship, the E/V Nautilus, to the waters off Nikumaroro, an isolated ring of coral and sand surrounding a turquoise lagoon.
Only four and a half miles long and one and a half miles wide, the island appears on most maps as a mere speck in the vast Pacific Ocean.

© Photograph by National Geographic

Inside the control room, crewmembers pilot remotely-operated vehicles (ROVs) and keep round-the-clock vigil in four-hour shifts.
“There are various theories about where Amelia’s plane landed, and some of them are a little wild,” says Ballard, a National Geographic Explorer.
Some people believe Earhart and navigator Fred Noonan ended up in the Marshall Islands, some say Saipan or even New Jersey, others that the plane crashed and sank.
“We’re going with the one that she actually landed.”

On July 2, 1937, Earhart and Noonan were aiming for Howland Island, which is even smaller than Nikumaroro.
After taking off from Lae, New Guinea, on the third to last leg of Earhart’s attempt to circumnavigate the globe, they failed to locate Howland and vanished without a trace.

The International Group for Historic Aircraft Recovery (TIGHAR) has spent the last several decades investigating the hypothesis that Earhart and Noonan landed their Lockheed Electra 10E on Nikumaroro when they couldn’t find Howland.

The researchers base their hypothesis on Earhart’s last radio transmissions.
At 8:43 a.m. on July 2, Earhart radioed the Itasca, the U.S. Coast Guard cutter awaiting Earhart at Howland: "KHAQQ [the Electra's call letters] to Itasca. We are on the line 157 337."
The Itascareceived the transmission but couldn't get any bearings on the signal.

The “line 157 337” indicates that the plane was flying on a northwest to southeast navigational line that bisected Howland Island.
If Earhart and Noonan missed Howland, they would fly either northwest or southeast on the line to find it.
To the northwest of Howland lies open ocean for thousands of miles; to the southeast is Nikumaroro.

The line-of-position radio message was the last confirmed transmission from Earhart, but radio operators received 57 messages that could have been from the Electra.
Wireless stations took direction bearings on seven of them.
Five of those crossed near Nikumaroro, then called Gardner island.

© Photograph by Rob Barrel, NAI'A Fiji

Ballard's search centers on Nikumaroro Island, an uninhabited atoll that's part of the Micronesian nation of Kiribati.
Some researchers believe Earhart and navigator Fred Noonan landed here and died as castaways.At the time of Earhart’s disappearance, the tide on Nikumaroro was especially low, revealing a reef surface along the shore long and flat enough for a plane to land.
If Earhart sent any of those 57 radio transmissions, the plane must have landed relatively intact.

The TIGHAR researchers theorize that Earhart and Noonan radioed at night to avoid the searing daytime heat inside the aluminum plane.
Eventually the tide lifted the Electra off the reef, and it sank or broke up in the surf.
The last credible transmission was heard on July 7, 1937.

Members of TIGHAR have traveled to the island 13 times, but never with the technological tools that Ballard has at his disposal.
The Nautilus is equipped with a multi-beam sonar on the hull, two ROVs with high definition cameras, an autonomous surface vehicle (ASV), and multiple drones—plus Ballard’s years of experience finding treasures under the sea.

© Photograph by National Geographic

Outfitted with an array of underwater sensors, E/V Nautilus works a grid-like search pattern Ballard likens to "mowing the lawn."On this expedition he’s aiming to discover where Earhart’s plane ended up after it tumbled off the reef.

It’s painstaking work.
The Nautilus didn’t approach the island directly but took a sweeping path that allowed the sonar to map the underwater terrain.
But the ship couldn’t get too close; the reef is extremely dangerous, as demonstrated by the wreckage from the S.S.
Norwich City that still dominates the northeastern shore of the island.

Once the Nautilus arrived at the island, a routine quickly developed: Send out the ASV (essentially a robot boat) to map the terrain near the surf.
When it returns, analyze the data to see what, as Ballard puts it, “comes out of the soup.” Ballard and his colleagues are looking for targets—anomalies—though a lack of them doesn’t mean nothing interesting lies below the waves.

Ballard puts great stock in laying eyes on his quarry.
“Everything I ever found was found visually,” he says.

© Photograph from Bettmann Archive/Getty images

Earhart and navigator Fred Noonan consult a map of the Pacific that shows the planned route of their round-the-world flight.That’s where the ROVs come in.
Usually launched at night, they can go as deep as 4,000 meters.
Hercules, a bright yellow box with a metal base, offers the first-person view, while smaller Argus keeps a camera pointed at Hercules.

The ROV pilots operate on four-hour shifts day and night, and mostly they don’t see much.
But on the first night they found wreckage—items that looked to be a propeller, a boiler, a crank shaft, and much more—all from the Norwich City.

It wasn’t the wreck Ballard was looking for, but it answered an important question: How deep could the plane go? The Norwich City debris clustered at depths between 100 to 300 meters.
“Anything of similar mass—part of a plane or part of a ship—would have been sliding down slope in that zone,” explains expedition leader Allison Fundis.
“We’re really focusing on that zone with the ROV dives.”

When the pilots do spot something, their reactions tend to be muted (unless it’s a charismatic creature such as a dumbo octopus).
During a recent watch a tube-shaped metallic object hove into view.
The Hercules pilot murmured, “It looks anthropogenic.
Should I pick it up?”

The answer was yes.
After a moment of hesitation, Hercules stretched out its arm and very slowly closed its pincers around the tube and delicately placed the item into a white storage container on its side.

What was it?
The answer would have to wait until the ROVs were recovered and the box could be opened, which wouldn’t be until the next day.

Spoiler alert: It was not part of Earhart’s plane.
Instead, it appeared to be a piece of oceanographic equipment—a sign that other explorers had been here before Ballard.

Ballard shrugs off false alarms, especially this early in the search.
“We did this nine days for the Titanic,” he says.

Amelia Earhart had planned to use her Electra to test the latest in aviation equipment—even nicknaming it the “Flying Laboratory.” By the end of this expedition to find the pilot and her plane, the Nautilus’s equipment will be tested to the limits, and the small island of Nikumaroro will be thoroughly mapped.
Whether her fate is discovered or not, maybe Earhart would be satisfied with that result.

Links :

• National Geographic : Robert Ballard found the Titanic. Can he find Amelia Earhart’s airplane?
• WP: This explorer found the Titanic. His new mission: Solve Amelia ..
• BBC : Can the man who found the Titanic find Amelia Earhart?  
• Popular Mechanics : The Guy Who Found the Titanic Is Now Looking for Amelia Earhart's ...
• Smithsonian : Why the Much-Publicized Mission to Find Amelia Earhart's Plane Is ...
• Newsweek : National Amelia Earhart Day: Facts, Quotes to Celebrate Aviation ...
• NYTimes : Where Women Made History … Right Under Your Feet
• CNN : Inside the secret US military mission that located the Titanic
• GeoGarage blog : Amelia Earhart mystery may finally be solved / Amelia Earhart: sonar image shows what may be ...