Overview of the area
The area studied here, which we will call maritime Southeast Asia (although part of it is directly attached to the Asian continent), lies roughly between the Tropic of Cancer and the Equator. It includes:
- Between the Tropic and the Equator
- In the north-west, southern Myanmar (Myanmar is the former Burma)
- Thailand, which borders Burma to the south and east.
- Southern Laos, central and southern Vietnam, and Cambodia
- Peninsular Malaysia, the southern extension of Thailand
- The Philippine archipelago, made up of a great many islands (Mindanao, Luzon, Palawan, Mindoro, etc.)
- Below the Equator
- Indonesia (a vast archipelago including the islands of Sumatra, Java, Bali, Sulawesi, etc.), which extends on both sides of the Equator.
- The island of Borneo, shared between Malaysia (north-west Borneo: Sarawak and Sabah) and Indonesia (Kalimantan).
To see a map of this region, click here.
Relief
The whole area consists mainly of mountains and plateaus, which are either extensions of the Himalayas or volcanic massifs.
- In southern Burma , two north–south mountain systems frame the valley of the Irrawaddy river: the Arakan range to the west and the Bilauktaung range, the southern extension of the Shan plateau in China.
- In Thailand, the north and west of the country are formed by the southern ends of the Himalayan arc, which slope gradually down to the south-east. In the east, a series of ridges surrounds the great Khorat plateau, drained by the network of eastward-flowing tributaries of the Mekong.
- The relief of Cambodia, consisting mostly of lowlands, includes a wide alluvial plain covering the whole central part of the country, occupied to the east by the Mekong valley and to the west by the valley of its main tributary, the Tonle Sap. The Cardamom Mountains stretch across the west of the country.
- The relief of southern Laos is characterised by lowlands.
- In central and southern Vietnam, south of the Red River delta, rises the long Annamite Range, which forms the mountainous backbone of the country; the south-east is occupied by the Cochinchina plain, in the centre of which lies the Mekong delta.
- The peninsular part of Malaysia has mountain ranges flanked by wide plains along each coast. The south of the peninsula is relatively flat. In the Malaysian part of the island of Borneo, the state of Sarawak consists of a marshy alluvial plain along the coast, rising to high mountains inland, especially in the east. The eastern part of the state of Sabah is covered by a vast plain. Mount Kinabalu, in the Crocker Range to the north-west, rises to 4,101 m.
- The relief of the islands of the archipelago ofIndonesia (the Sunda Islands) combines high mountain massifs, often volcanic, with vast plains (the largest on the island of Sumatra). The archipelago stretches over more than 4,000 km from east to west. Apart from Java and Sumatra, the Indonesian islands consist of a high central volcanic massif surrounded by coastal plains. The Indonesian part of Borneo (Kalimantan) includes the extensions of the ranges in the north of the island, and a large southern plain.
- The Philippines form a vast archipelago (more than 7,000 islands, 90% of them uninhabited). Almost all are volcanic, with mountainous terrain and rugged relief due to intense seismic activity. Plains are rare and generally small, except on the two largest islands (Mindanao and Luzon), where they spread out within wide valleys.
Because of this mountainous relief, and apart from the Irrawaddy in Burma and the Chao Phraya and Mekong in Thailand, Laos, Cambodia and Vietnam, a multitude of small rivers have cut deep valleys through all the rugged areas.
Climate
The climate naturally depends on the location already mentioned, between the Tropic of Cancer and the Equator:
- It is therefore tropical (Burma, Laos, Cambodia, Vietnam, Malaysia), influenced by the monsoons: the summer monsoon (from April–May to October–November depending on the region), or rainy season, brings heavy rainfall (sometimes violent, in the form of typhoons) carried by winds blowing from the Pacific Ocean from the north-east; temperatures are high (around 30°C). The winter monsoon, coming from the Indian Ocean from the south-east between November and February, brings less rain and lower temperatures. In short: temperatures between 20 and 30°C, high humidity and practically no truly dry season in this part of the area.
- In Indonesia the climate is equatorial and the seasons are almost reversed compared with the regions above: northern monsoon from November to February and dry south-west monsoon from May to September, with a narrower temperature range (25° / 28°).
- This climate naturally has local variations due to latitude, altitude and aspect: high-altitude regions are very wet, with lower temperatures; Laos and Cambodia, sheltered by mountains, receive less rain; the islands of eastern Indonesia are drier; the western Philippines is sheltered from the many violent typhoons that strike these islands from the east every year.
