Geologi

Merapi represent a nature glamor amazing. with the trapeze top opening up at west. This volcano oftentimes vomits the heat material, such as dusty rain and hot sand, blast of pyroclastic flows and rock fall of lava.  The eruption cycle is short enough.  that is about 2 – 7 years.  Merapi needs special attention, because in every happened by the eruption will menace human being at least 40,000 people.        .
Pyroclastic flows often generate disaster. Apart of this gliding sediment can reach the radius more than 10 km with the temperature more than 600 °C and have speed about 300 km /hour. This hot material in the form of dust and sand, the grain size is about 4 - 0.5 mm. Grain size analysis of pyroclastic flows which is taken away from area is near with eruption center till to the slope, showing pattern bimodal, the grain size is 4 mm and 0.250 mm, its mean is the grain size is unsorted. This sediment is effect of process the precipitation by turbulence.

Gunung Merapi merupakan gunungapi yang terletak paling selatan dari sederetan Merapi – Merbabu- Suropati - Telomoyo dan Ungaran.  Deretan gunungapi ini berada di bagian tengah dari propinsi Jawa Tengah. Selama kurun waktu kejadian letusan 1786-2001 titik letusan setalu mengalami perpindahan arah.
Sejarah mencatat letusan Merapi mulai abad 17 hingga kini, sedikimya telah 80 kali gunungapi ini meletus dan mengguncangkan kawasan di sekitarnya. Bencana besar akibat  letusan,  seperti kejadian      tahun  1672,  1822,  1832,  1872,  1930  dan  1994 sesungguhnya memberikan arti  yang sangat  penting, karena  pada kejadian  letusan  ini cukup banyak menelan korban baik harta maupun jiwa.
Dengan fenomena letusan tersebut, penduduk di sekitar Merapi masih merasa enggan untuk meninggalkan tanah kelahirannya. Hal ini karena masih kentalnya hikayat budaya, kepercayaan yang terpatri secara turun-temurun,  serta kecintaannya terhadap sumber kehidupan mereka, walaupun bahaya  letusan  setiap saat mengancam jiwa dan harta  bendanya.  Telah banyak warisan yang terkubur akibat letusan, sebagai saksi atas kejadian letusan dimasa lalu dan kini sebagai pembelajaran sekaligus diambil manfaatnya untuk generasi kini.  Sebagian warisan peninggalan kehidupan manusia tersebut kini nampak tersingkap, akibat dilakukan penggalian.

Abstrak
Wilayah Kabupaten Kebumen bagian selatan merupakan  pantai bergelombang lemah yang merupakan baglan kawasan pantai selatan Pulau Jawa yang memanjang  dari barat - timur. Secara umum pantai selatan merupakan pantai yang curam, namun di sela - sela jajaran pantai curam tersebut terdapat suatu dataran yang umumnya diisi  oleh  endapan . placer berupa endapan pasir yang membawa  berbagai macam material diantaranya mengandung pasir besi. Mineral yang mengandung logam meliputi : hematit, ilmenit, magnetit dan rutil, sedangkan kuarsa, piroksen  dan hornblende sebagai penyerta.
Tujuan penelitian ini adalah  untuk  mengetahui kualitas endapan pasir  besi  melalui  pengamatan
singkapan, pengambilan conto pasir besi, kemudian dilakukan pengujian laboratorium untuk mengetahui komposisinya.
Dari basil penelitian diketahui bahwa pasir besi yang mempunyai kandungan Fe signifikan terdapat di
bagian barat (mendekati Sungai Cingcingguling) dan bagian timur (mendekati Sungai Luk Ula).


Abstract

Southern part of Kebumen is undulating coastal plain, which it is part of south coastal Java that
length from west - east.
The generally the southern coast is steep, but between them have coastal plain filled by placer
sediment The placer sediment bringing assorted of material among others contain of iron sand.
The metal mineral in the iron sand are hematite, ilmenite, magnetite and rutile, while quartz, pyroxen and hornblende as accessories mineral.  Aim of this research is to know the quality of iron sand sediment by out crop observation, sampling iron sand and than examination in laboratory to know this composition.                                                                                                                 
From the research known that iron sand having content of significant Fe, there are in western and
east of coastal area.

ABSTRAK Gunungapi Pandan adalah gunungapi yang terbentuk di atas batuan sedimen Tersier dari zona Kendeng yang tersedimentasikan di cekungan Jawa Timur. Selain menghasilkan potensi minyak bumi, seperti ladang minyak Cepu dan Bojonegoro, daerah ini juga menghasilkan potensi panas bumi. Sebagai sumber panas dari sistem panas bumi adalah batuan beku yang terbentuk dari proses magmatisme. Jenis batuan yang terbentuk oleh proses magmatisme dalam sistem panas bumi Pandan adalah basaltik-andesitik dan andesit hornblenda yang berafinitas afinitas kalk alkali K tinggi-sedang yang terletak di tatanan tektonik busur kepulauan. Interaksi batuan panas dari proses pasca magmatisme dengan cairan hidrotermal menghasilkan manifestasi mata air panas dan travertine kalsit di daerah penelitian. Prediksi suhu bawah permukaan air panas dari analisis geotermometer silika yang terkandung di Banyukuning dan Jarikasinan menunjukkan kesetimbangan kristobalit Beta (70 o C) dan suhu kuarsa (120 o C). Untuk mempelajari tentang magmatisme dan fluida panas bumi menggunakan metode petrografi dan analisis petrokimia (metode spektrometri fluoresensi sinar-X) untuk sampel batuan beku. Sedangkan untuk mempelajari jenis fluida dan geotermometer fluida geothermal menggunakan data dari peneliti sebelumnya. Studi penelitian ini diharapkan dapat memberikan informasi tambahan di bidang panas bumi dan magmatisme di daerah ini. ABSTRACT Pandan volcano is a volcano formed on Tertiary sedimentary rocks from the Kendeng zone deposited in the basin of East Java. In addition to generating petroleum potentials, such as Cepu and Bojonegoro oil fields, this area also generates geothermal potential. As a source of heat from the geothermal system is igneous rock formed from the magmatism process. The type of rock formed by the process of magmatism in the Pandan geothermal system is basaltic-andesitic and hornblende andesite are medium-high K calk alkaline affinity located in the island arc. The interaction of hot rock from post magmatism process with hydrothermal fluid resulted in the manifestation of hot springs and calcite travertine in the study area. Prediction of the subsurface temperature of hot water from geothermometer silica analysis contained in Banyukuning and Jarikasinan show cristobalite Beta equilibrium (70 o C) and quartz temperature (120 o C). To study about magmatism and geothermal fluid using petrographic method and petrochemical analysis (X-ray fluorescence spectrometry method) to the sample of igneous rock. While to study the fluid type and geothermometer of geothermal fluid using data from previous researchers. This research study is expected to provide additional information on the field of geothermal and magmatism in this area.

Activities of Old Lawu volcano in the past resulted in various soil development in the south side of the volcano, especially in the area of the east side of Wonogiri and west side of Ponorogo, that located in the Java island. This area is also famous as herbal crops producer for raw materials of traditional herbal medicine industry. The purpose of this research is to identify the process of exposure of the parent materials in the Old Lawu volcanic environment, the development of the soil parent materials, and the mineralogy variation.  Four Sites with different geological formation were observed, and each Site was selected for soil profile identification on the process of weathering of rocks.  All layers of each profile were then sampled and then sand fraction of the fine earth particle was determined for the mineral type using X-ray diffraction (XRD).  The results showed that materials of the Old Lawu volcanic activity that was of quaternary period had sized material of gravel, san...

Pandan volcano is a volcano formed on Tertiary sedimentary rocks from the Kendeng zone deposited in the basin of East Java. In addition to generating petroleum potentials, such as Cepu and Bojonegoro oil fields, this area also generates geothermal potential. As a source of heat from the geothermal system is igneous rock formed from the magmatism process. The type of rock formed by the process of magmatism in the Pandan geothermal system is basaltic-andesitic and hornblende andesite are medium-high K calk alkaline affinity located in the island arc. The interaction of hot rock from post magmatism process with hydrothermal fluid resulted in the manifestation of hot springs and calcite travertine in the study area. Prediction of the subsurface temperature of hot water from geothermometer silica analysis contained in Banyukuning and Jarikasinan show cristobalite Beta equilibrium (70oC) and quartz temperature (120oC). To study about magmatism and geothermal fluid using petrographic metho...

Artisanal and small gold mining activity in Wonogiri Regency has long been done with problems on environmental quality. This study was aimed to analyze the levels and spatial distribution of heavy metals in the mining area. Survey of  mining and amalgamation sites, sampling the soil and tailings had been conducted. There were 66 samples of soil and tailing were collected, analysis of heavy Fe, Mn, Pb, Hg, As and Co, using X-ray fluorescence (XRF). Normal distribution test of data was conducted using the Kolmogorov-Smirnov and Shapiro Wilk.  The spatial distribution of heavy metals was described using Krigging method. Contents of most heavy metals in the area studied were high, except for Co. According to the distribution pattern of heavy metals indicated that the contamination caused by the mining.

A wide and deep soil profile (around 1200 cm) was observed at Ketep Park West Slope of Merbabu volcano Central Java, Indonesia to identify the soil morphology, physical and, chemical and mineralogical properties.  Results showed that several soil development processes occurred in each volcanic deposits with different characteristics.  Most soil layers met some of andic soil properties criteria such bulk density <0.9 g.cm-3, P retention of >85%, and (Alo + ½ Feo) >2.0%.  A thin melanic material showing black color layer was found at the lower part of the soil profile, i.e. in depth from 726 to 798 cm.  The dominant material in most soil layers is an allophane.  Minerals in the sand fraction were dominated by labradorite and augite, with some layers were hypersthene and green hornblende.

The Ijen volcano has Pleistocene age (294.00 ± 0.03 Ma), and this stratovolcano was very acidic crater water with a pH of 0-1. The acidic crater water seeps into the Banyupait river flow. Asembagus is a research area located on the northern slope of the Ijen volcano, and the Banyupait River drains this. The acidic river water flows from the Ijen Crater Lake, so the pH of the water river was very acidic. This study used several different analytic methodologies with some previous researchers, namely using the method of geological mapping, pH measurement, spectrophotometry, IRMS (Isotope Ratio Mass Spectrometer), and the technique of Induced Coupled Mass Spectrometry (ICP-MS). Besides, the petrographic analysis is used to determine the composition of rock minerals due to rocks interacting with acidic water. Banyupait River water in the Asembagus area has a pH of river water around 3-7.3, SO4 (220-683 ppm), and the type of water is meteoric water. Also, concentrations of Ca, K, Mg in th...

Nannofossil analyses of Miocene to Pleistocene, the section of Nglebur River, Jiken, Blora of Central Java included of Rembang Zone, North East Java Basin. This study uses 70 samples from this section. The result of this analysis consists of 18 genus was obtained with 57 species of nannoplankton. The research method used in field study (measure section) quantitative analysis. The samples from taken include fine-grain stone (marl, shale) and carbonaceous. The river section that has been selected consist of a continuous sediment sequence from Miocene (Wonocolo, Ledok, and Mundu Formation) to Pleistocene (Lidah Formation). The sample preparation uses the smear slide method and species determination uses Nannotax3 determination. The biostratigraphy consist of 11 zones, and there consists of 2 Partial Zones and 9 Interval Zones. These Zone are Discoaster hamatus Partial Zone/NN9, Interval Zone of Discoaster hamatus–Discoaster quinqueramus /NN10, Zone of Discoaster quinqueramus /NN11, Zone of Discoaster quinqueramus–Ceratolithus rugosus/NN12, Zone of Ceratolithus rugosus–Discoaster asymmetricus/NN12, Zona of Discoaster asymmetricus–Pseudoemiliania lacunosa/NN14, Zona of Pseudoemiliania lacunosa with Reticulofenestra pseudoumbilicus/ NN15, Zona of Reticulofenestra pseudoumbilicus with Discoaster surculus/NN16, Zona of Discoaster surculus–Discoaster asymmetricus/NN17, Zona of Discoaster asymmetricus–Discoaster brouweri/NN18, and Partial Zone Discoaster brouweri and Gephyrocapsa caribbeanica/NN19.