Mapping America

By Robert D. Ballard
10/19/2013 10:15:04 AM

The following is an excerpt from the November issue of National Geographic magazine.

America has had two great ages of exploration. The one that every schoolchild learns about began in 1804, when Thomas Jefferson sent Meriwether Lewis and William Clark on their epic journey across North America. The other one is just beginning. During this new age of exploration we will go farther than Lewis and Clark and learn the secrets of territories beyond even Jefferson's wildest imagination. Yet it seems safe to say that most Americans don't know anything about it.

In 1983 Ronald Reagan expanded America's sovereign rights the natural resources with 200 nautical miles of its coasts. This region-roughly the size of the continental United States-has not been fully explored. Credit: Juan Jose Valdes and Rosemary Wardley, NG Staff, Ryan Morris, NGM Staff, Theodore A. Sickley, Sources: U.S. Department of State; NOAA; Center for Coastal and Ocean Mapping/Joint Hydrographic Center

Few realize that the single largest addition to the American domain came on March 10, 1983, when President Ronald Reagan, with the stroke of a pen, expanded the country's sovereign rights 200 nautical miles from its shores "for the purpose of exploring, exploiting, conserving, and managing natural resources." By establishing an exclusive economic zone (EEZ), Reagan roughly doubled the area within United States boundaries, as Jefferson had with the Louisiana Purchase.

Other countries have increased their jurisdiction over natural resources through EEZs and are eager to add more. Under the 1982 UN Convention on the Law of the Sea, which the United States has not joined, countries can claim sovereign rights over a larger region if they can prove that the continental shelf-the submerged portion of a continent-extends beyond their EEZ and meets certain other conditions. The United States potentially has one of the largest continental shelves in the world.

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