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ANCIENT VOLCANOES OF NGLANGGERAN

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					                    ANCIENT VOLCANOES OF NGLANGGERAN
                                          CHAPTER I

                                        PRELIMINARY


I.1.Background
      This ancient volcano located in the village Nglanggeran district. pecking, Gunungkidul to
travel to this location is only 30-40 minutes away from jogja. According to the geological study
area, Mount Nglanggeran is Ancient Volcano. Age mountains are interesting to scientists
because they want to know the geological genesis (formation) volcano and predict how the
tectonic conditions at Nglanggeran mountain is still active. Initial studies previously estimated
age Nglanggeran mountain is about 50 million years. However, a recent study found the
mountain is dead since 18 million years ago.

I.2.Problem
      How is the process of mountain formation until no longer active, and what geological
processes that affect it?


I.3 Objectives and Benefits

      Inform what is ancient volcanic. In order for students and readers know anything about
ancient volcanic Nglanggeran.




By : gilang052@gmail.com                                                                 1
                                         CHAPTER II
                                         DISCUSSION


II. 1 Definitions


      Mount Nglanggeran is Ancient Volcano. Age mountains are interesting to scientists
because they want to know the geological genesis (formation) volcano and predict how the
tectonic conditions at Nglanggeran mountain is still active. Initial studies previously estimated
age Nglanggeran mountain is about 50 million years. However, a recent study found the
mountain is dead since 18 million years ago. This ancient volcano located in the village
Nglanggeran district. pecking, Gunungkidul to travel to this location is only 30-40 minutes away
from jogja.


        According to Awang Harun Satyana, a geologist Indonesia, Nglanggran Formation and
formations Kebo Butak and Breezy are Oligo-Miocene volkanisme product for the first time by
Verbeek and Fennema (1896, examined again by Bothe, 1929, 1934, and compiled van
Bemmelen , 1949) called sebagaiOAF (Oud Andesiet Formatie - Old Andesite Formation or
OAF. This is volkanisme submarin (van Bemmelen, 1949) that are turbidite.




                        Figure 1.1 Profile of Ancient Volcanic Nglanggeran


By : gilang052@gmail.com                                                                 2
II.2 Genesis


     In the theory of plate tectonics, OAF and all formations ekivalensinya in West Java
(Jampang, Gabon) and East Java (Puger) (see regional evaluations that have been published in
the Proceedings of PIT IAGI 2003: Satyana and Purwaningsih, 2003, Oligo-Miocene carbonates
of Java : Tectonic Setting and Effects of Volcanism) is a path from Oliogo-Miocene volcanics
(Late Oligocene-Early Miocene), which is now the Southern Mountains physiographic south of
Java. Path parallel to the long axis of Java volcanics was caused by partial melting experienced
by the Indian oceanic crust at 100-200 km depth beneath the zone subduksinya in submarine
ridge south of Java today. Based on the absolute age using the K-Ar (Soeria-Atmadja, 1994)
volkanisme ended at 18 Ma (Early Miocene section below).
       After that, at 12 Ma (Middle Miocene) began to occur pelandaian subduction slope
(Wadati-Benioff zone) so that the zone of partial melting part moves to the north and generate
volkanisme Middle Miocene age which was sustained until the Quaternary and the left lane and
center Nglanggran volcanic eruption in surroundings. Switching path about 50-100 miles
volcanics to the north has been disabled all volcanoes in the southern path - there is no feeder
partial melting of magma results to this volcano.




                                 Figure 1.2 Genesis Of Subduction



By : gilang052@gmail.com                                                                3
II.3 Stratigraphy




Figure 1.3. Regional stratigraphic column of the South Mountain region (DRR Rahardjo., 1977; Surono
              DRR., 1992). Lithology in the study area belong to the Formation Semilir.

       Stratigraphy of the Southern Mountains, including the study area, have been studied by
Rahardjo DRR. (1977) and Surono DRR. (1992) and the results are presented in Figure 1.3. As
the oldest rocks in the Southern Mountains is the old metamorphic rocks Pratersier, which is
exposed in the hills Jiwo, District Bayat, Klaten regency, Central Java Province. In the Southern
Mountains to the west, in the metamorphic rocks are successively deposited Limestone
Formation-Wungkal, Kebo-Butak, breezy, Nglanggeran, Sambipitu, Oyo, Wonosari, Kepek, and

By : gilang052@gmail.com                                                                   4
deposition of alluvium. Limestone Formation-Wungkal composed of limestone and quartz
sandstone, which is also exposed in the hills Jiwo, Bayat. The main constituent formations
lithologies Kebo-Butak to Nglanggeran Formation is volcanic rock, in the form of pyroclastic
material, lava epiklastika nor coherent. Regionally, the Tertiary volcanic rocks in the study area
in ¬ put in Formation breccia consisting breezy and rich batulapili pumis, and tuff (Bronto DRR.,
2005;     Bronto      and      Mulyaningsih,      2001;      Mulyaningsih,      1999,      2005).
     Formation Sambipitu bottom is composed of volcanic rocks klastika, but getting to the top
containing carbonate materials, while Oyo Formation and Wonosari almost entirely composed of
limestone. Tertiary rock units on top are Kepek Formation, which is composed of marl and
limestone layered. The whole ba-host Pratersier and overlain by Tertiary are not aligned by
alluvium sediment, mainly from Merapi Volcano. The main fault in this area is the Fault Opak,
the trending southwest – northeast.




By : gilang052@gmail.com                                                                  5
                                       CHAPTER III
                                      CONCLUSION


III.1 Conclusion


      Mount Nglanggeran aged about 50 million years. However, a recent study found the
mountain is dead since 18 million years ago. Nglanggran and Kebo Butak formations and Breezy
are Oligo-Miocene volkanisme product for the first time by Verbeek and Fennema (1896,
examined again by Bothe, 1929, 1934, and compiled van Bemmelen, 1949) refers to as OAF
(Old Andesite Formation or OAF).




By : gilang052@gmail.com                                                            6

				
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