ABSTRACT
In the Eastern Archipelago the mountains are of two ages—an older phase governed by erosion and a newer phase just appearing at the present day. Earthquakes show that movement is taking place now along certain definite lines in definite regions, whereas other regions (the western part except the region which is bounded by the Indian Ocean) are stable. The same story as is told by earthquakes is told by upheaved coral reefs on all the islands. Those islands, which have an altitude from the bottom of the sea of not much less than 30,000 ft., are higher than the Himalaya. The old mountain chains diverge in many parts of the Archipelago, such as at the north-western corner of Sumatra and in the north-eastern corner of Borneo. The Kainozoic strikes of these mountains cut through the directions of the present rows of islands and sometimes at high angles. These strikes therefore do not coincide with the coasts of many of the islands. The rows of islands clearly show the present movement because erosion did not yet affect them strongly, and their movement is clearly demonstrated by the characteristics of the upheaved coral reefs.
