N. H. FISUER DEI'AItT/tIENT O F
I~AND$ A N D
M|INES~ ItABAtrlo
Note on the Vulcanological Observatory at Rabaul ~ The main Vulcanological Observatory at Rabaul is being built on the northern rim of the Blanche Bay caldera, about 600 feet above sea-level. The site overlooks Blanche Bay and the town of R a b a u l , and commands an excellent view of the two volcanoes Tavurvur and Raluan (Vulcan), also of the older craters (probably extinct) Rabalanakaia and Sulphur Creek. The Observatory will consist of an insulated cellar 25 X 15 feet for the housing of instruments, over ~vhich will be built an office, laboratory, dark room, observation room and a small museum. A two component horizontal ar, d a vertical Wiechert seismograph are being installed, both with a heavy mass of 80 kilograms. Two tiltmeters of an Italian model will measure the north-south and east-west components of any tilts that may affect the site. Other necessary instruments, radio receiver, contact clock earthquake annunciator, thermometers; cameras, microscope, gas analysis apparatus, gas masks, a grinding lap for making thin sections, telescope, binoculars, etc. will be included in the equipment. cc In addition to the central observatory, observation posts will be established near each of the craters, Raluan and Tavurvur. Both of these will consist of tunnels, driven into the old caldera wall opposite the volcanoes, fitted with gas proof doors, and connected by telephone with the main observatory. Small two component tromometers will be installed in each post, and two component tiltmeters. At both of these posts and at the central station meteorological observations will be taken daily.
* 186 * The work of" the station will consist of the recording and study of all tremors registered, both at the main station and at the observation posts, and the sending out of. monthly seismological bulletins. Temperatures, at a great number of fixed points, of hot springs, .fumaroles
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and solfataras, and ground temperatures, will be taken, in many cases daily, instead of weekly as previously. Analyses of solfatara gases will be made at regular intervals. Tilts, ground subsidence or elevation will be measured by the tiltmeters, by levelling fixed points at intervals and by tide gauges. Field mapping and petrological research will be carried out as opportunities offer, and visits will
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be made from time to time to active volcanoes of the Mandated Territory. Cooperation of persons residing near volcanoes will be sought and all possible information regarding eruptions and the state of activity of the volcanoes will be collected.It is hoped later to build further tromometers and install them at other places in the Territory. The Observatory is now under construction and the instruments have been on order for some time, so it is probable that the station will be in operation before the end of the current year. The accompanying sketch plan shows the position of the Observatory and the town of Rabaul, and the volcanoes and observation posts J.
