Bougainville, the largest island in the whole group, is the northernmost except for little Buka, from which it is separated by a channel only about half a mile wide. The interior, imperfectly known, contains at least one massive mountain range following its length. Two active volcanoes, Balbi and Bagana, are respectively 10,171 and 9850 feet. The island is heavily forested. Some of the coastal areas are fertile, and there are a few copra plantations.
Guadalcanal, the largest island in the protectorate, is mainly of volcanic formation with an irregular and very rugged chain of mountains following the southern shore fairly closely, but separated from the north coast by gently sloping plains. The highest peak, Popomanasiu, 8005 feet, is near the center of the south coast. Numerous rivers follow direct courses to the sea. The whole island is densely wooded with the exception of the western part of the northern plain, where there are extensive areas covered with alang-alang grass.
The population is concentrated mainly on the north coast, where the natives depend mainly on fish, yams, and coconuts; taro is the staple crop of those still living in the interior. Before the Second World War, Guadalcanal had been more developed than most other large islands in the Solomons, and large coconut plantations were located along the fertile north coast, but these have suffered severely from immature nutfall. The new capital of the Solomon Islands Protectorate is at Honiara on the north coast near Henderson airfield. It has an established road net and is centrally located with reference to the copra industry. During the Second World War fierce fighting took place on the island and in the seas adjoining Guadalcanal, and the first important victory over the Japanese was won there.
Structurally Ysabel is a single chain of volcanic mountains, which, in most parts, dips gently to a low-lying coastal strip. The whole island is forested. It is believed that Ysabel has been considerably depopulated, and formerly the inhabitants were subjected to headhunting raids from New Georgia. The more important areas of settlement are in the extreme southern and northern parts of the island, and here are found several coconut plantations. At the northern end of Ysabel a complex group of islands extends northwestwards, and the Gijunabeana islands extend 4 or 5 miles off the east coast.
Malaita, known locally as Mala, is separated by a narrow, tortuous passage from Little Mala. The island is basically of volcanic formation with superficial deposits of coral limestone on the lowlands near the coast. Forested mountains, with elevations up to 4275 feet, follow the main axis, but the interior is mostly unsurveyed. The population consists of vigorous natives who have a reputation both as fighters and workers, and there are still occasional reports of tribal warfare. Most of the villages of this island have contacts with Europeans through young men who are laborers on coconut plantations, mostly on other islands.