CHAPTER VII. PIROCLASTIC ROCK

CHAPTER VII. PIROCLASTI ROCK DEFINISION: Piroklastik Rock is a volcanic rock that Texturized klastik generated by a series of processes that are associated with volcanic eruptions, with the composer's original material is different. Material is terendapkan composer and terkonsolidasi before the reworked by water and ice.

MINERAL COMPOSITION Juvenil Group (essential) When material is issued directly from the composer magma, consisting of padatan, depressed or particles from a liquid to freeze and the crystal (crystal pyrogenic). Cognate Group (Accessory). When the material penyusunnya from hamburan material originating from the eruption sebelumya, from the same or Gunungapi volcanic body is older than the crater wall. Accindental Group (bahan asing) When the material is penyusunnya material hamburan rock that came from non Gunungapi basic form of rock or frozen rock, sediment, methamorf, so have a uniform composition

PIROCLASTIC ROCK TEXTURE Variations in shape, pembundaran and pemilahan rock piroklastik similar to the rock klastik sediments in general. Teknologi dan Rekayasa

MINERAL COMPOSITION Sialis Minerals Consists of : Kwarsa (SiO2). Feldsfar, both K-Feldsfar, Na – Feldsfar, or Ca Feldsfar. Feldspatoid, is a group of minerals that occur if the solution is not in a state of magma or less saturated akan silica matrix

B. Ferromagnesia Minerals Is a group of rich mineral akan uterus bond Fe-Mg silicate and sometimes followed by Ca-silicate. Minerals are present as groups of minerals: Piroksen, is important in the mineral rock Gunungapi Olivin, which is rich in minerals and iron, magnesium and silica poor.

C. ADDING MINERAL frequently-Present MINERALS: HORNBLENDE BIOTIT MAGNETIT ILMINIT

PIROCLASTIC ROCK CLASSIFICATION Piroklastik material can be grouped according to size as follows (schmid, 1981, vide Visher, 1984). Ukuran butir (mm) Sebutan (piroklastik) Endapan piroklastik Tak terkonsolidasi terkonsolidasi > 64 Bomb, block Bomb, block tephra Aglomerat, Breksi Piroklastik 64 – 2 lapilus Tephra lapili Batu lapili 2 – 1/16 Debu kasar Tuff, debu kasar < 1/16 Debu halus Tuff, Debu Halus

Feculence PIROKLASTIK TAK TERKONSOLIDASI Bomb Gunungapi. Bomb is a clump-clump of lava have size> 64 mm, and some or all plastis at the time tereropsi. Can be divided into 3 types: A.Bom ribbon (ribbon bombs), the aft bomb like the flute, and most of the bubble-bubble-aft direction with the same. Bamb have this very condensed form the core of the material has a terkonsolidasi lmenyudut and retakan skin is not regularly B.Bomb terrace (cored bomb), which has lomb core material terkonsolidai first, perhaps the rest of the fragment-fragment erupsi Gunungapi of the same. C.Bomb crust of bread (bread crust bombs), that is a bomb outside the cracked-cracked square seem like a crust of bread rise, this is caused by the skin quickly and refrigerate menusut.

2. Gunungapi block (block vulcanic) Rock piroklastik is generated by the explosive eropsi of rock fragments that have been used to condense more with size> 64 mm. Block-block is always retire to a corner shape. 3. Lapili. Latin derived language that is lapilus, the name for the explosive erupsi Gunungapi the size of 2 mm-64 mm. Aside from the rock fragments, or I sometimes consist of minerals augit, olivin, and plagioklas. 4. Gunungapi dust. Piroklastik rock is the size of 2 mm-1/256 mmyang produced by the ejection of magma due erupsi explosive. However, there is also dust Gunungapi going penggesekan process because at the time erupsi gaDebu Gunungapi still not yet under the circumstances terkonsolidasi.

PIROKLASTIK SEDIMENTARY YANG TERKONSOLIDASI Lithifikasi deposition is due to fall-piroklastik Breksi piroklastik: Rock is organized by block-block Gunungapi, which have experienced Consolidation in the number of> 50% and 25% Â ± lapili and dust. Aglomerat (Agglomerat). Ang is a rock formed by Consolidation of materials dominated by dg womb where the fetus bomb Gunungapi lapili and ash <25%. Lapili stones (lapilli stone) is the dominant rock consists of fragments lapili with the size of 2-64 mm. Tuff Is the deposition of ash volcano that has experienced Consolidation with ash contents reach 75%. Macamnya: - Tuf f lapilli (lapili tuf)-Tuff aglomerat (agglomerat tuff)-Tuff breksi piroklastik (pyroclastic breccia tuff)

BATUAN AKIBAT LITHIFIKSI ENDAPAN PIROKLASTIK ALIRAN Ignimbrit (ignimbrite) Adalah batuan yang disusun dari endapan material oleh aliran abu. Material –material ini dominan terdiri dari pecahan-pecahan gelas dan pumice yang dihasilkan oleh buih-buih magma asam. Breksi aliran piroklastik (pyroclastic flow breccia). Adalah breksi yang dominan disusun oleh fragmen yang runcing serta ditransport oleh glowing avalance (akibat aliran awan panas). Vitrik tuff Adalah batuan yang dihasilkan dari endapan piroklastik aliran terdiri dari fragmen abu dan lapilli, telah mengalami lithifikasi dan belum terelaskan. Welded tuff. Adalah batuan piroklastik hasil dari piroklastik aliran yang telah terlitifikasi dan merupakan bagian dari ignimbrit (istilah yang dipakai di A.S dan Australia)

SOME ENDAPANPIROKLASTIK Forming Mechanism 1.Sediment fall piroklastik (pyroclastic fall). Namely piroklasti stack diendapkan through the air. Generally well layered, composite structure of the grain, including: breksi piroklastik, aglomerat, lapilli, tuff. 2. Piroklastik sediment flow (pyroclastic flow). That is the material directly from the central erupsi then teronggukan on a place. Include: avalance hot, glowing avalance, collapse avalance lava, hot ash avalance. Generally, high temperature 500-650 degrees. Sediment fill the cavity morphology. 3. Feculence piroklastik surge (pyroclastic surge). Cloud that is a mixture of solid material and gas (water vapor) that have a mass meeting with the low and move high above the turbulent surface. Pemilahan generally have good, hard-smooth and layered structure of the primary baik.Mempunyai: laminating, perlapisan to the planar wave. The most typical sediment structure have cross rustle, and cornered a small melensa.

NAMING BY FISHER, 1966 DAN WILLIAM, 1954.

BY FISHER, 1960

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