In the context of Southeast Asia, the Philippines represent, from a physical-structural point of view, the unstable margin of the continent on the Pacific side. The area they occupy is marked by crustal phenomena linked to the evolution of the southeastern edge of the Asian continental mass. The presence in the archipelago of oceanic trenches, which exceed 10,000 m in depth, suggests that this evolution is at the same time connected to that of the circumpacific belt, the “belt of fire”, of which the Philippines, with their volcanism and the high seismicity, are one of the most active areas. The basic structure is formed by crystalline and schistose rocks which, starting from the Miocene (Cenozoic eraor tertiary), underwent successive and intense orogenetic crises; thus originated the folds that make up the mountainous backbone of the archipelago. At the same time there were strong volcanic manifestations, which covered large surfaces of the islands with magmatic materials of considerable thickness; volcanism, although somewhat reduced, is still active, as well as seismicity, which during the century. XX gave rise annually to approx. 150 earthquakes, some of which were disastrous. The orography is tormented and varied: hence the often bizarre shape of the island contours and the extreme fragmentation of the country: the Filipinos have calculated more than 7000 islands, the largest of which are Luzon and Mindanao, located at the northern and southern extremities of the archipelago, including Samar, Negros, Palawan, Panay, Mindoro, Cebu, etc. The characteristic and fundamental features of the relief are given by the Cenozoic mountain alignments, which in turn are connected with the systems of the Sunda archipelago. There are three main axes: the alignment that, in the meridian direction, crossing Luzon and Mindanao, connects on one side to the ridge of Formosa, on the other to that of Celebes; and the two alignments, roughly parallel, which give rise to the ridges of Palawan and the Sulu islands, continuing then in the reliefs of Borneo. All the islands are mountainous; only in Luzon and Mindanao do extensive depressions interpose between the chains, filled by alluvial soils, which represent the most vital spaces in the country. The fertile plain that opens towards the bay of Manila, on the island of Luzon, forms the heart of the entire archipelago; the Western mountains or Zambales, to E la, overlook the plain to the W Central Cordillera, the largest of the three main mountainous alignments of the island as well as the highest (Mount Pulog, 2934 m), and which, as the name implies, runs in the middle part of the territory. Towards the E the Central Cordillera dominates the Cagayan valley, bordered on the opposite side by the Sierra Madre: this is the third great chain of Luzon, which develops along the eastern coast of the island. Mindanao’s orography is very complex; dominated by imposing hills, the island culminates at 2954 m in Mount Apo, an active volcano which is the highest peak of the archipelago. The coasts, usually rocky, dominate the characteristic stretches of the sea that take their name from the islands themselves; the largest marine space is that enclosed between the Sulu and Palawan (Sulu Sea). Deep up to 5,580 m, it corresponds to a pit between the two ridges, surmounted by different island formations: Palawan is practically a single and steep mountain range that exceeds 2,000 m in altitude; the Sulu are a myriad of islets fringed by coral reefs.
Due to the mountainous and fragmented conformation of the islands, the hydrography is fragmented and therefore devoid of extensive basins. Naturally, the major rivers are those that drain the depressions of Luzon (Cagayan, Agno, Pampanga) and Mindanao (Agusan, Mindanao). In volcanic areas there are crater lakes, such as that of the Taal volcano in Luzon.
According to findjobdescriptions, the high rainfall is at the origin of the dense forest that covers extensive regions of the Philippines; there are various subtropical essences typical of south-east Asia, as well as a particular species of mahogany (of the genus Hovenia) with hard and precious wood, called Philippine mahogany. Coconut palms are frequent at the edges of the forest, which also border the coasts – often fringed with mangroves – and cultivated areas. At higher altitudes there are continental species such as conifers, well represented in the mountains of Mindanao; on the island, however, and even more so in Luzon, the landscape appears to be largely profoundly transformed by the work of man. The fauna is very rich and includes numerous endemic species, especially birds. The uncontrolled felling of trees constitutes one of the main environmental problems of the country together with air pollution, especially in large urban areas, and the degradation of the coasts, caused by the illegal construction of housing structures. The Ministry has ordered the establishment of an environmental protection office and the government has approved the establishment of numerous protected areas, covering 5% of the territory, in all regions.