Volcanic in origin, the Philippine Islands are the higher portions of a partly submerged mountain chain. The mountains are the principal topographical feature on the smaller islands. The larger islands, particularly Luzon and Mindanao, have a more diversified topography, with fertile river valleys in the interior. Mountain ranges generally parallel the coasts, forming narrow coastal plains. The inland plains and valleys are the most densely populated areas.
On Luzon the Sierra Madre mountains form the longest range of the Philippines, extending along the island’s eastern, or Pacific, coast. The parallel ranges of the Cordillera Central, to the west about 80 km (50 mi) across the Cagayan River Valley, contain Luzon’s highest peak, Mount Pulog, at 2,930 (9,613 ft). Near this peak, mountainside rice terraces have been cultivated for hundreds of years. Farther south the important rice-growing region of the Central Luzon Valley, well irrigated by numerous rivers, extends from Lingayen Gulf to Manila Bay. The rugged Zambales Mountains, containing Mount Pinatubo (1,780 m/5,840 ft), form the valley’s western boundary, leading south to the Bataan Peninsula, the sheltering landmass for Manila Bay. Luzon becomes narrow at its southern end, curving to the southeast in a long, mountainous extension called the Bicol Peninsula. Here a string of volcanoes includes the cone-shaped peak of Mayon Volcano, rising to a height of 2,525 m (8,284 ft) near Legaspi.
Mindanao is similarly formed, with coastal mountain ranges and inland valleys, notably those of the Agusan and Mindanao rivers. The Diuata Mountains bordering the eastern coast form the most prominent range on the island. The country’s highest point, Mount Apo (2,954 m/9,692 ft), rises in the south near the Mindanao River basin. The large Zamboanga Peninsula extends from western Mindanao, hooking southward toward the Sulu Archipelago.
The Visayas include seven major islands, among them the republic’s third largest island, Samar, with an area of 13,100 sq km (5,100 sq mi). The most easterly of the Visayas, Samar is connected by bridge to the adjacent island of Leyte; both islands are relatively undeveloped and have dense jungle forests. To the west are Bohol, site of the tourist attraction known as the Chocolate Hills, hundreds of cone-shaped hills with vegetation that turns brown during summer; Cebu, a long, narrow island and the most densely populated island in the Philippines; Negros, which developed from the mid-1800s as the center of the Philippine sugar industry; and Panay, where many agricultural crops are grown in the rich volcanic soils of the densely populated coastal plain of Iloilo Province. Masbate, in the north central Visayas, is noted for its gold and copper mines.
Most of the Philippine Islands are clustered in a predominantly north-south direction. In the southwest, two island groupings deviate from this predominant direction: the long, narrow island of Palawan and its offshore islands and, farther south, the approximately 900 small islands of the Sulu Archipelago. Both island groupings extend southwest toward Borneo with the Sulu Sea between them. The Sulu Archipelago includes many coral islands and reefs. Palawan Island is believed to be the first Philippine island to have been settled by people who migrated from the Southeast Asian mainland during prehistoric times.
