Gunung Api Purba Ngelanggeran Yogyakarta : Berdasarkan bukti endapan yang di hasilkannya, di tengarai pernah terjadi erupsi katastropik Gunung Api Purba Semilir yang kekuatannya nyaris setara dengan Supervolcano Toba disumatera (74.000 Gunung yang lalu) dan Supervolcano Yellowstone di Wyoming, amerika serikat (2,1 juta tahun yang lalu) , kekuatan erupsi gunung api burba semilir saat itu diperkirakan tak kurang dari 10 kali lebih besar dari erupsi gunung Tambora(1815). 100 kali lebih besar dari erupsi gunung Krakatau (1883) dan 1000 kali lebih besar erupsi Gunung St. helena di Washington Amerika Serikat (1980).

inilah masa-masa gunung api purba mengalami kejayaanya di pulau jawa, namun pada kisaran 16 hingga 2 juta tahun yang lalu (kala miosen tengah hingga pliosen akhir) kegiatan magmatisme di gugusan gunung api purba ini mulai jauh berkurang. paragraph pada kisaran 12 juta tahun yang lalu (kala miosen tengah). mulailah terjadi pelandaian kemiringan penunjaman lempeng samudra indo-australia, sehingga proses pelelehan yang menghasilkan magma ikut bergeser kearah utara, proses ini terus berlanjut sampai sekitar 1,8 juta hingga 11.500 tahun yang lalu (kala pleistosen) dan masih berlanjut hingga saat ini (kala holosen) meninggalkan gugusan gunung api purba yang telah terbentuk sebelumnya disisi selatan pulau jawa.

pergeseran jalur vulkanik yang mencapai jarak sekitar 50 hingga 100 kilometer kearah utara ini, secara otomatis telah menonaktifkan semua gunung berapi purba, karena suplay magma hasil pelelehan dibawah permukaan bumi telah bergeser ke utara, aktifitasnya gunung api purba seperti Nglanggeran, semilir dan kemungkinan pusat-pusat erupsi lainnya, berangsur-angsur mulai turun, bahkan bisa dikatakan nyaris tak bersisa lagi. kondisi pulau jawa pun mulai relatif stabil , meskipun kegiatan magmatisme tetap ‘terpelihara’ oleh alam, bergeser ke sebelah utara.

It is said that, based on the evidence of the sediment, it was suspected that catastrophic eruptions of the Acient Volcano have accurred, whose strength is almost equivalent to Toba Supervolcano in Sumatra (74.000 year ago)and Yellowstone Supervolcano in Wyoming, United States (2.1 million years ago). the strength of the eruption of Semilir Acient Volcano at that time was estimated to be no less than 10 times greater than than the eruption of Mount Tambora (1815), 100 times greater than the eruption of mount Krakatau(1883) and 1000 times greater eruption of Mount St. Helena in Washington, United States(1980).

These are the times when ancient volcanoes experienced glory on java. but in the range of 16 to 2 million years ago (middle miocene to the late pliocene) magmatism activities in this ancient volcanic cluster began to decrease considerably.

in the range of 12 million years ago (middle miocene period), the slope of the indo-australian oceanic plate slope began to oncur, so that the melting process that produces magma also shifted to the north. this proces continued until around 1.8 million to 11,500 years ago(pleistocence period) and still continues to this day (holosen period), leaving a cluster of ancient vocanoes that have been formed before on the south side of java.

the shift of the volcanic path that reaches a distance of about 50 to 100 kilometers to the north, has automaticaly de activated all ancient volcanoes, because the supply of melted magma under the surface of the earth has shifted north. the activity of ancient volcanoes like Nglanggeran, Semilir and possibly other eruption centers, gradually began to fall, it could, even be said to be almost no more. the condition of java also became relatively stable, even though magmatism activities remained ‘maintained’ by nature, shifting to the north.

want to know more depth, come directly to the “Museum History Of Java”, Jl Parangtritis km 5.5, Sewon, Bantul, Yogyakarta.

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