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Southeast Asia is like a challenging puzzle. Some of its main pieces, its countries, are divided into smaller pieces. Learning how
the region’s pieces fit together will help you answer a question geographers ask: What makes it a region?
Landforms and Resources How are the landforms of Southeast Asia’s mainland different from the landforms of its islands? Southeast Asia can be divided into two main parts. One part is a mainland area. The other part is an insular area, or an area made up
of islands. (Insular comes from the Latin word insula, meaning “island.” Another term that comes from insula is peninsula. It means
“almost an island.”)
The mainland sits at the southeastern corner of the Asian continent. It borders two countries with the world's highest populations: China
and India. In this area, the Indian Ocean meets the Pacific. Thousands of islands stretch across miles of tropical waters.
Peninsulas and Islands Most of the mainland sits on a large peninsula. It sticks out southward from the Asian continent, between India and China. It is known
as the Indochinese Peninsula, or simply Indochina.
Southeast Asia has 11 countries. Six of these are located at least partly on the mainland peninsula. Cambodia, Laos, Myanmar (also
known as Burma), Thailand, and Vietnam are found on the peninsula. The western region of Malaysia is also located there. The tiny
island country of Singapore sits just off the southern tip of the Malay Peninsula. A bridge connects Singapore’s main island to the
peninsula.
The region’s other four countries and the eastern part of Malaysia lie in the Malay Archipelago. An archipelago is a group of islands.
The Malay Archipelago is the world’s largest in area. It contains more than 24,000 islands. They range from mainland Southeast Asia to
Australia. Among the islands are 7 that rank among the 20 largest in the world: New Guinea, Borneo, Sumatra, Sulawesi, Java, Luzon,
and Mindanao.
Indonesia is by far the largest country in Southeast Asia. It is made up of more than 17,000 of the islands in the Malay Archipelago.
Indonesia shares the islands of Timor, New Guinea, and Borneo with other countries. East Timor is one of the world’s newest countries.
It is located in the eastern half of Timor. Malaysia’s eastern region spreads across northern Borneo, surrounding the small country of
Brunei.
The northernmost islands in the Malay Archipelago are the Philippines. They form their own archipelago east of the mainland. The
Philippines make up a country of more than 7,000 islands and islets.
Mountains and Volcanoes Much of the land in Southeast Asia is rugged and mountainous. On the mainland, mountain ranges generally run north to south. They
include a group of ranges along the western edge of Myanmar. These ranges follow the border between Myanmar and Thailand. They
form the "backbone" of the Maylay Peninsula. The Annamese Cordillera stretches through Laos and Vietnam. It runs parallel to the
mainland’s eastern coast.
Many of the mountains on Southeast Asia’s islands started as volcanoes. The islands lie along the Ring of Fire. The Ring is a
seismically active zone that encircles much of the Pacific Ocean. Most of the world’s earthquakes and volcanic eruptions happen here.
In Southeast Asia, four major tectonic plates meet. They are the Eurasian Plate, the Indo­Australian Plate, the Pacific Plate, and the
Indian Plate. The meeting of these plates produces great pressure and tension. It has fractured Earth’s crust into many smaller plates
across the region. This has caused the fractured physical landscape. It has also produced the volcanoes and the many islands of the
region.
Indonesia has more than 100 active volcanoes—more than any other country in the world. Most are in a long arc along the country’s
southern edge. One of the most famous volcanoes is Krakatoa. It lies between the islands of Sumatra and Java. In 1883, Krakatoa
erupted and collapsed into the sea. It triggered tsunamis that killed about 36,000 people.
An even deadlier tsunami occurred in Indonesia in 2004. There was a powerful undersea earthquake off the coast of Sumatra. It
produced huge waves that slammed into coastal areas of Southeast and South Asia. More than 230,000 people were killed.
Natural Resources Southeast Asia has a variety of mineral resources. These include tin, copper, lead, zinc, and gold. Gemstones such as rubies are also
found there. Indonesia, Malaysia, and Thailand rank among the world’s top tin producers. Indonesia produces roughly a fourth of the
world’s supply of this commodity.
Teak, mahogany, ebony, and other hardwood trees grow in the region’s tropical forests. These woods have long been in high demand.
Many Southeast Asian countries export wood and wood products. Some limit logging to slow deforestation.
Southeast Asia is rich in fossil fuels. Indonesia and Malaysia rank among the world’s top 30 oil producers. They also are among the top
15 natural gas producers.
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Analyzing What effect has the Ring of Fire had on the formation of the region?
Skills Practice
Look for words you know on labels of things. Think about what the words mean.
Bodies of Water Why does Southeast Asia have so many different seas? Bodies of water are key parts of Southeast Asia’s geography and identity. The region includes about 5 million square miles (13 million
sq. km). Only a third of the area, however, is land.
Oceans and Seas The Malay Peninsula and Indonesia’s Sunda Isles represent the boundary between two oceans. To the west and south lies the Indian
Ocean. To the north and east lies the Pacific Ocean. The region’s largest seas are the South China Sea and the Philippine Sea. West
of the Malaysian peninsula is the Andaman Sea.
Some of the busiest lanes in the world pass through Southeast Asia’s seas and their waterways. One of its most important waterways
is the Strait of Malacca. About a quarter of the world’s trade, including half of all sea shipments of oil, passes through it. The strait links
the South China Sea and Andaman Sea. Singapore controls the Strait of Malacca. As a result, Singapore has become one of the most
important ports in the world.
River Systems Southeast Asia’s longest rivers are on the mainland. Most rain flows into one of five major rivers. From west to east, they are the
Irrawaddy, Salween, Chao Phraya, Mekong, and Red. They generally flow from northern highlands to southern lowlands on their way to
the sea.
The Irrawaddy, Salween, and Mekong begin high on the Plateau of Tibet. The Irrawaddy flows almost straight south through a valley in
Myanmar’s center. The river plays a major role in the region’s transportation system. Its vast fertile delta is important for farming.
The Salween runs southward through the eastern part of Myanmar. It forms part of that country’s border with Thailand. Like the
Irawaddy, it drains into the Andaman Sea. The Mekong is Southeast Asia’s longest river. It flows about 2,700 miles (4,345 km) through
or near Myanmar, Thailand, Laos, Cambodia, and Vietnam. The river’s drainage basin is twice the size of California. Its huge delta is
one of the world’s most productive agricultural regions.
Analyzing Why do you think Southeast Asia’s longest rivers are found on the mainland and not on islands?
Climate, Vegetation, and Wildlife In what ways does Southeast Asia’s location shape its climate? Climates in Southeast Asia are generally hot and humid. Much of the region receives more than 60 inches (152 cm) of rain fall each
year. The region also has a wide variety of habitats. It is home to a great number of plant and animal life.
A Tropical Region Latitude and air currents play major roles in Southeast Asia’s climates. Nearly the entire region lies within the Tropics. This zone
receives the hottest, most direct rays of the sun. From November to March, the direct rays of the sun are south of the Equator in the
Southern Hemisphere. This produces areas of low pressure. As a result, monsoon winds blow across the region from the northeast to
the southwest. These winds bring cooler, drier air to much of the mainland. They also bring heavy rains to the southern Malay
Peninsula and the islands. From May to September, the pattern reverses. The direct rays of the sun produce low air pressure north of
the Equator. This causes monsoon winds to blow from the southwest to the northeast. They bring warm air and rain to the islands and
the mainland.
Most of the region’s land is surrounded or nearly surrounded by the sea. This keeps the air tempeture balanced. Elevation also affects
weather conditions. Temperatures in the highland areas are generally cooler than in the lowland areas. Indonesia’s highest peak is
Puncak Jaya (PUHN­chock JAH­yuh). There are glaciers at the top of this mountain, even though it is close to the Equator. The effects of the sea, elevation, and air currents create four climate zones. The southern Malay Peninsula, the southern Philippines,
and most of Indonesia have a tropical rain forest climate. The northern Philippines, the northern Malay Peninsula, and the coastal
mainland have a tropical monsoon climate. They experience rainy and dry seasons. Most inland areas have a tropical savanna climate.
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This climate does not have clear rainy and dry seasons. The northernmost mainland has a humid subtropical climate. Summers there
are hot and wet. Winters are mild and dry.
Weather in Southeast Asia sometimes turns deadly. Strong tropical storms called typhoons form over warm Pacific Ocean waters. They
slowly spin westward, often reaching the Philippines. Typhoon winds can pass 150 miles (241 km) per hour. Winds and heavy rains
sometimes last for days. Typhoons may destroy buildings. They can cause severe floods, ruining crops and killing many people.
Plants and Animals Southeast Asia has a wide variety of flora, or plant life. Indonesia, for example, has more than 40,000 species of flowering plants.
About 5,000 of these are orchid species. It also has more than 3,000 species of trees.
Much of the region is covered in tropical rain forests or mixed forests. These mixed forests have both evergreen and deciduous trees.
Coastal areas have forests of mangrove trees with aboveground roots. These forests form a border between land and sea.
Southeast Asia also has a wide variety of fauna, or animal life. Many species are endemic, or found nowhere else in the world. Human
activity can harm their environments. Fires, logging, mining, and agriculture have reduced many habitats. Poaching, or illegal hunting,
also threatens wildlife.
Identifying What are three factors that affect climate in Southeast Asia?
LESSON 1 REVIEW
Reviewing Vocabulary
TEKS: 22A
1. Determining Word Meanings What peninsula forms a long bridge between mainland and insular Southeast Asia?
Answering the Guiding Questions
TEKS: 6B, 21B
2. Categorizing What are some of Southeast Asia’s most important mineral resources?
TEKS: 6A
3. Analyzing Why are most of Indonesia’s volcanoes located along its southern edge?
TEKS: 5A
4. Analyzing What is the relationship between Singapore’s status as one of the most important ports in the world and its location at the
southern end of the Strait of Malacca?
TEKS: 4D
5. Identifying What two physical features affect the climates in the region?
TEKS: 7B
6. Persuasive Writing Write a persuasive letter urging the government leaders of Southeast Asia to take action to protect the region’s
tropical forests from uncontrolled logging. Discuss the importance of the forests and the consequences of deforestation. Explain how
ecotourism may provide a solution for economic growth.
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