Within the body of physical geography, the Earth is often split either into several spheres or environments, the main spheres being the atmosphere, biosphere, cryosphere, geosphere, hydrosphere, lithosphere and pedosphere. Geomorphology, hydrology, biogeography, climatology, meteorology, pedology (soil science), paleogeography, coastal geography, oceanography, quarternary science, landscape ecology, geomatics, and environmental geography are parts of physiography. The following sections discuss the majority of these subjects in Indonesia and its vicinity.
|Fig. 1.1. Eastern hemisphere geographic grid|
- Indonesia 1,904,569 km2
- Papua New Guinea 462,840 km2
- Philippines: 298,170 km2
- Northwest Borneo (East Malaysia & Brunei): 198,847 km2
- Timor Leste: 15,410 km2
- Christmas Island: 161 km2
|Fig. 1.3. SE Asian Archipelago (darker color) as treated in this book. The brown outline shows Indonesian border.|
|Fig. 1.4. Areal comparison of Indonesia to USA (above) and to Europe (below)|
The plate tectonics concept, which was introduced in late 1950's (after the publication of van Bemmelen's book) suggests that these oceanic basins developed at the plate margins. The plate movement generate collisions and the oceanic plates in this region subducted underneath other plates. These subductions oceanic plates generated low reliefs. In many parts the collisions are still active and generate earth quakes (Fig. 1.6).The positive relief in Himalaya is caused by a collision of Indian-Australian continent and Asian continent.
|Fig. 1.6. Epicentre distribution in Indonesia (source: USGS)|
In 2004 a major earth quake in the Indian Ocean, close to Aceh has killed at least 280,000 people. Further detail of this incident is available in wikipedia (Click here for link)
|Fig. 1.7. Gravity anomaly map of Indonesia by Sandwell and Smith (2009)|
|Fig. 1.8. Major volcanoes of Indonesia (USGS, 2001)|
|Fig. 1.10. Zoogeographic border lines in the Malay Archipelago.|
|Fig. 1.11. Rain fall distribution in Indonesia (source BMG)|
The Philippine Islands are often struck by typhoons. These are cyclones revolving counter clockwise, which form over the Pacific Ocean, as a rule east of the Ladrone Islands. Of those passing across the Philippine Archipelago, practically all occur North of Mindanao, and most of them strike Luzon.
|Fig. 1.12 Seasonal changes of rain distribution in SE Asia from 1979-2001 (D. Kirono, Pers Comm, based on the CMAP data set of Xie et al 2003).|
|Fig. 1.13. Comparison of SE Asian rivers (with red underline) and other rivers in the world.|
Coleman and Huh from Lousiana State University did a comparison of world river systems, including a number of rivers from Southeast Asia. Fig. 1.13 shows examples of the graphs they prepared on river length and average annual discharge. The Southeast Asian rivers are generally have small catchment areas and relatively short. The size of islands limit the river system. Mekong River is an exception as it is located in the Asian continent. On the other hand Chao Praya, which is also in the Asian continent is relatively small as it is controlled by fault zones.
LIXIVIATION OF THE SOIL
|Fig. 1. 14. Forest distribution of Southeasian Archipelago (University of Maryland).|
|Fig. 1.15. Asia soil map by ISRIC, 1997|
THE GROUPING FOLLOWED IN THIS BOOK
a. The Sunda shelf and smaller islands.
b. Larger Sunda Islands bordering the Shelf Sea (Borneo, Sumatra, Java and Madura).
a. Sin Cowe Reefs in the South China Sea.
b. The Philippine Archipelago.
d1. Northern Moluccas.d2. Southern Moluccas.
e. Lesser Sunda Islands.
f. Ridges South of Java and West of Sumatra.
g. Andamans and Nicobars.
a. New Guinea.
b. Sahul Shelf with the Aru Islands.
c. Christmas Island. This grouping will be followed in this chapter.
2. Smaller Islands on the Sunda Shelf.
4. The Malay Peninsula.
2. Northern Moluccas.
3. Sulawesi. .
4. Southern Moluccas (Banda Arcs).
5. Lesser Sunda Islands.
7. Sumatra and the Islands to the West of it.
8. Andamans and Nicobars.
2. Christmas Island.
3. The Sahul area a. The Sahul Shelf. b. The Aru Islands.
1. The Sunda Mountain System.
2. The East-Asiatic Arcs.
3. The Melanesian System.
4. The circum-Australian System.
|Fig. 1.16. Simplified tectonic map of SE Asia|