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Transcript for America\'s New Frontier, segment 09 of 11
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The Hawaii GLORIA survey shows that the ninety-eight percent of the island chain below sea level has much to tell about the growth and degradation of the islands and the resulting impact of these processes on the surrounding ocean floor.
There were several things in the Hawaiian E. E. Z. we found that were really major discoveries, and it's hard to rank them, but if I had to rank them, I would say the most important was the discovery of many giant landslides, among the biggest on earth, very big, a thousand cubic kilometers which is something very hard to imagine, and there were very many of these, and they seemed to happen, oh, on the average, every fifty thousand or hundred thousand years.
The GLORIA imagery clearly shows a gigantic landslide that came out from two different sources, part from the eastern side of Oahu and part from the eastern side of Molokai, and those two deposits merged out on the sea floor. The furthest deposits or blocks from these landslides are over one hundred kilometers from the islands, and individual blocks are so large, they had been previously mapped as seamounts rather than landslide blocks. Now, this is one of the most notable of the landslides, but there are actually about seventeen different landslide deposits around the islands.
Another thing of major significance are very large young lava flows which have drastically affected our understanding of the Hawaiian hot spot and the nature of Hawaiian volcanism, which seems to have a much wider effect than we previously knew and, of course, has a wide submarine effect that we never even suspected.
One of the areas where the GLORIA imagery has provided a base map for future, for further sampling was in the area offshore Kahala volcano located here, where there are series of six drowned coral reefs that range in age from the youngest near the shoreline is fifteen thousands years old to the deepest offshore is about five hundred thousand years old and is now at a depth of almost fourteen hundred meters. They indicate that the island has subsided fourteen hundred meters in the last five hundred thousand years and that the shoreline used to be way out here.
{{{BACKGROUND NOISE}}} Using the GLORIA images as a guide and the Hawaii undersea research lab Pisces Five Submersible as a platform, U. S. G. S. marine geologists have sampled a number of the submerged Hawaiian reefs. This process of collecting bottom samples and other data that can be correlated directly to a spot on a GLORIA image is called ground truthing. Ground truthing is vital to understanding exactly what the GLORIA images are showing. While channels and seamounts stand out clearly on the images, important details about the type and distribution of sediments are not so easily defined. Bottom cores, underwater photography and video. and more detailed sonar surveys make up the bulk of the ground truthing process. The few ground truthing surveys conducted have shown that GLORIA's sound pulse is actually penetrating the bottom and is imaging as much as the upper ten meters of sediment. This complicates the interpretation of the images and calls for more extensive and widespread ground truthing studies. Ultimately the ground truthing work will transform the GLORIA images into continuous geologic maps of the entire ocean floor in the U. S. exclusive economic zone.