The Truk (pronounced Chuk) group (151° 22′ to 150° 04′ east longitude, 7° 7′ to 7° 41′ north latitude) is about 900 miles north of Rabaul and 650 miles southeast of Guam. Truk is an almost, or complex, atoll with a barrier reef that varies from 30 to 40 miles in diameter. There are about 40 small motus on the reef, but only one of these, Pis (pronounced peace) Island, is permanently inhabited. The lagoon has a circumference of about 140 miles and contains 6 fairly large high islands and many lesser ones. About 100 of the lesser islands of the lagoon bear names. The total dry land of the island group is about 39 square miles. Tol, or Ton, is the largest of the islands and has the highest elevation, 1483 feet. The other important islands in order of their size are Moen, Fefan, Dublon, Udot, and Uman. Elevations on these islands vary from about 950 feet to a little more than 1000 feet.
Truk is the deeply eroded summit of a great volcanic dome that rises from a submarine plateau. Although the islands of the eastern part of the plateau appear to be fairly stable, there has been some recent subsidence of Truk as is evidenced by drowned river valleys.
Tol is the most densely populated of the islands, but native life on it has been less disturbed than on the other high islands. The natives of Tol live in small scattered villages; those on the other high islands were concentrated into larger villages during the German and Japanese occupations.