Ngelanggeran Ancient Volcano Yogyakarta: Based on the sediment evidence it produces, it is suspected that a catastrophic eruption occurred at the Semilir Ancient Volcano, whose power was almost equivalent to the Toba Supervolcano in Sumatra (74,000 years ago) and the Yellowstone Supervolcano in Wyoming, United States (2.1 million years ago). The eruption strength of the Semilir Ancient Volcano at that time is estimated to have been at least 10 times greater than the eruption of Mount Tambora (1815), 100 times greater than the eruption of Mount Krakatau (1883), and 1000 times greater than the eruption of Mount St. Helena in Washington, United States (1980).
This marks the peak period of the ancient volcano’s glory on the island of Java. However, between 16 and 2 million years ago (from the Middle Miocene to the Late Pliocene), the magmatic activity in the cluster of ancient volcanoes started to significantly decrease. Around 12 million years ago (Middle Miocene), the subduction plate of the Indo-Australian oceanic plate began to flatten, causing the magma-producing process to shift northward. This process continued until about 1.8 million years ago to 11,500 years ago (Pleistocene) and persists until today (Holocene), leaving behind the cluster of ancient volcanoes that had previously formed on the southern part of Java Island.
The volcanic shift, which moved about 50 to 100 kilometers to the north, automatically deactivated all the ancient volcanoes, as the magma supply from below the Earth’s surface shifted northward. The volcanic activity of ancient volcanoes like Nglanggeran, Semilir, and possibly other eruption centers gradually decreased, to the point where it can be said that it almost disappeared. The condition of Java Island also started to stabilize, although magmatic activity was still “preserved” by nature and shifted to the north.
Want to know more depth, come directly to the “Museum History Of Java”, Jl Parangtritis km 5.5, Sewon, Bantul, Yogyakarta!