Regions
The 11 largest islands make up more than 90 perscent of teh total area. Only about 460 islands are larger than 2.6 sq km, and about 1,000 are populated. Luzon and Mindanao are the two largest islands. The mountains are the principal topographical feature on teh smaller Islands. The larger islands, porticulartly Luzon and Mindanao, have a more diversified topography, with fertile river valleys in teh interior. The Philippine Islands are part of the so-called Ring of Fire, an area encircling the Pacific Ocean. The Philippines includes about 20 active volcanoes and many inactive, or dormant volconoes. The most active is Mayon Volcano. Mount Pinatubo caused widespread damage when it erupted in 1991 after lying dormant for about 600 years. Mount Apo, the country's highest mountain, is an active volcano with three peaks.