The Mystery Of Sandy Island

Sandy Island. An Island the size of Manhattan,  discovered in 1876,  had disappeared.   During the  25  day  expedition led by Maria Seton, a young scientist from University of Sydney,  to the Coral Sea aboard the Australian research vessel,  the RV Southern Surveyor.They noticed several maps showed a long black island where the onboard map showed nothing, but open sea. Maria and the scientist went to where the maps indicated where the island was only to find that it was, indeed, nothing, but opened water. That, of course , created a lot of questions.  Where did a 15 mile long and 3 mile wide island go to? Did it erode into the ocean? Was it an island so flat that it was covered by water when  the ocean rose and uncovered when the ocean level was lower? Did it sink?

 But Where Did Sandy Island go?

Sandy_island_GeoGarage

 

It was a mystery. In fact, it was enough of a mystery that the scientists decided to find out what happened to Sandy Island. They noticed that the island was shown as a big blob on  a cached verision of Google Earth. However, the island showed up on many of their own scientific data sets, including the General Bathymetric Chart of the Oceans.  All showed Sandy Island clearly in a remote area west of New Caledonia. Yet no island.

Maria continued to look into the undiscovery of the island. Sandy island appeared on the 1908 edition of a British admiralty map, which indicated that Sandy Island had been discovered in 1876 in French territorial waters by the whaling ship Velocity. The location and shape of the island on the 1908 map corresponds to what can be seen in the modern databases. the was undsicovered several time but kept popping up. A shadowy presence. One one map but not the other. Some maps labeled it as “ED” or Existence Doubtful.  The French removed the island in 1974.sandy_island_location_image

Sandy Island kept coming back ,though. The island was clearly marked  on a 1982 U.S. Defense Mapping Agency map.  It was given the French name “Ile de Sable “. The annotation read : “Reported 1876. Reported to be about 4 miles east, 1968.” Sandys finally found the World Vector Shoreline Database (WVS) created by the U.S. Miltary.  Old Hard copy charts were converted into a digital fromat but the Database. BUT there were errors. Maybe even decades old , the errors were hidden in the new data set. Those errors migrated to other databases used by scientists such as the Global Self-consistent, Hierarchical, High-Resolution Shoreline Database (GSHHS).

Even though map making has come along way since the days when Cartographers marked uncharted areas with “here be sandy_islanddragons”errors are still made.   David Titley, a retired rear admiral who served in the Navy for 32 years and served in the position of oceanographer and navigator, says “Just because a map looks professional, and just because a digital map may have impressive bells and whistles, doesn’t mean that the underlying data has been scrubbed of errors,When we look at these computer displays, with the three-dimensional imagery and colorized, it can give you a sense that we know more than we do. A lot of people in the Navy don’t always understand the difference between having a chart and having the survey data that formed that chart.”

 

Other than an error among map makers, somebody must of saw something at one time. The whaling vessel who first reported the island in 1876 may have seen one of the pumice stone rafts that float throughout the ocean. Pumice is a light rock that is produced during volcanic eruptions. Large mats of pumice can float on the ocean before breaking to pieces.

Pumice raft

Pumice raft

“In volcanic terrains you can get islands that are temporarily there and then disappear. I have seen floating mats of pumice that form and drift around for several years after a marine volcanic eruption,” said Bruce Molnia, a research geologist at the U.S. Geological Survey.

 Seton points out  that an eruption near Tonga in 2001-2002 produced a pumice raft that traveled about 2,000 miles toward Australia, and it passed within 13 miles of the location of “Sandy Island”. The island that never existed. Mystery..Solved

 

Sources:

http://www.washingtonpost.com/national/health-science/scientist-unravels-mystery-of-coral-seas-ghostly-sandy-island/2013/04/14/76316606-a508-11e2-8302-3c7e0ea97057_story.html

http://www.gebco.net/about_us/news_and_events/gebco_and_sandy_island.html