Satellite photo of Johnston Atoll, about 1,390 km (860 mi) west of Hawaii. Four islands compose the total land mass of 2.6 sq km. Johnston and Sand islands are both enlarged natural features, while Akau and Hikina are two artificial islands formed by coral dredging. Johnston Island, by far the largest, somewhat resembles the flattop of an aircraft carrier and contains an airstrip. Photo courtesy of NASA.