The Current Geographic Setting
1. Explain how plate tectonics play a role in creating the conditions for active volcanism in the Philippines and
The irregular shapes and landforms of the Southeast Asian mainland and archipelago are the result
of the same tectonic forces that were unleashed when India split off from the African Plate and
crashed into Eurasia.
The curve formed by Sumatra, Java, the Lesser Sunda Islands (from Bali to Timor), and New
Guinera conforms approximately to the shape of the Eurasian Plate’s leading edge. As the Indian-
Australian Plate plunges beneath the Eurasian Plate along this curve, hundreds of earthquakes and
volcanoes occur, especially on the islands of Sumatra and Java. Volcanos and earthquakes also
occur in the Philippines, where the Philippine Plate is pushing against the eastern edge of the
2. Explain how the monsoons and ITCZ bring rain to Southeast Asia most of the year.
The rainfall is the result of two major processes: the monsoons (seasonally shifting winds) and the
intertropical convergence zone (ITCZ), the band of rising warm air that circles Earth roughly
around the equator. The wet summer season extends from May to October, when the warming of
the Eurasian landmass sucks in moist air from the surrounding seas. Between November and
April, there is a long dry season on the mainland, when the seasonal cooling of Eurasia causes dry
air from the interior continent to flow out towards the sea. On the many islands, however, the
winter can also be wet because the air that flows from the continent picks up moisture as it passes
south and east over the seas. The air releases its moisture as rain after ascending high enough to
cool. With rains coming from both the monsoon and the ITCZ, the island part of Southeast Asia is
one of the wettest areas of the world.
3. The human settlement of Southeast Asia is ancient. Describe the two prehistoric waves of people into the region and
the landforms that facilitated this settlement. Where have settlers come from in the last 2000 years? What has
prompted these newer waves of migration?
The first, Australo-Melanesians, a group of hunters and gatherers from the present northern Indian
and Burman parts of southern Eurasia, moved into the exposed landmass of Sundaland about
40,000 to 60,000 years ago. They were the ancestors of the indigenous peoples of New Guinea,
Australia, and Indonesia’s easternmost islands. Very small numbers of their descendants still live
in small pockets in upland areas elsewhere, notably in the Philippines, Borneo, Java, Sumatra, the
Malay Peninsula, and the Andaman Islands.
The second, people from southern China began moving into Southeast Asia about 10,000 years
ago, at the end of the last ice age. Their migration gained momentum about 5000 years ago, when
a culture of skilled farmers and seafarers from southern China, named Asutronesians, migrated
first to Taiwan, then to the Philippines, and then into island Southeast Asia and Malay Peninsula.
Newer waves of migration have come due to signs of the region’s increasing economic success.