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Figure 5. Status of the GLORIA mapping program and location

of CONMAP parcels.

Mapping the EEZ: The First Million

Square Miles

By Bonnie A. McGregor

The USGS effort to map the seafloor of the U.S. Exclusive Economic Zone (EEZ) reached a major milestone in 1987. The GLORIA (Geologic Long-Range Inclined Asdic) sidescan sonar system has now mapped over a million square nautical miles of seafloor in 3 years. One-third of the EEZ has been mapped completely, including the seafloor adjacent to the lower 48 States, to Puerto Rico and the U.S. Virgin Islands, and to Alaska in the Bering Sea region (fig. 5). The mapping is continuing on the Research Vessel M/V Farnella. The EEZ south of Alaska and around the Hawaiian Islands will be completed next, which will culminate the EEZ mapping for the 50 States by 1990. Efforts will then focus on the U.S. territories and possessions in the Pacific.

The M/V Farnella began the mapping of the Bering Sea in summer 1986 and completed it in July 1987. As in earlier EEZ mapping ventures, the mosaics are showing scientists geologic features that they had not imagined. The sonar mosaic of the floor of the Bering Sea shows extensive dissection of the continental margin and the northern slope of the Aleutian Ridge by some of the largest submarine canyon systems ever identified. Large, well-defined channel systems that emanate from submarine canyons in the southeastern corner of the Bering Sea extend for several hundred miles across the abyssal plain. Flow patterns on the seafloor appear to have formed by sheet flow as sediment is transported across the Aleutian Basin. The dominant erosional and transport processes active along the margins of the Bering Sea are a variety of types of mass movement ranging from small debris flows to massive submarine landslides and slumps of blocks of sediment measuring miles in diameter and thickness. Within the Bering Sea, Bowers Ridge is a crescent-shaped ridge, which was believed to be inactive because of its lack of seismicity and its flat crest. GLORIA images provided a new perspective of

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