Dipuncak pegunungan Idjen terdapat 3 buah bangunan rumah, masing - masing letaknya berjauhan, yaitu : (1) Pondok Kawah Idjen; (2) Pondok U.G.A. (Pos Urusan G.Api) sebelah Selatan; (3) Pondok U.G.A. (Pos Urusan G.Api) sebelah Utara.
Pada tanggal 23 Februari 1956, kami diberi tugas untuk memeriksa G.Kelud, berkenaan dengan terjadinya ombak didalam setinggi 5m, pada tanggal 20 Februari 1956, yang disebabkan oleh longsornya dinding kawah sebelah Barat-Daya dari kawah.
Pada permulaan bulan Februari oleh pos penjagaan D.G.B di Kawah Idjen telah dilaporkan adanya tanda - tanda kegiatan dari G. Raung, yang terlihat mulai tanggal 31 Januari 1953.
Pada tanggal 18 Desember 1951 penulis berangkat ke Gunung Kelut untuk mempelajari keadaan G.Api tersebut. Sesudah letusan dan teristimewa mempelajari turunnya lahar dingin dan kemungkinan- kemungkinan yang dapat terjadi sebagai akibat dari aliran tersebut.
Laporan ini membahas Gunung - Gunung berapi yang berada di daerah Jawa Timur, yaitu: (1) Kawah Idjen; (2) Gunung Raung; (3) Gunung Semeru; dan (4) Gunung Bromo.
Among the number of active volcanes of Jawa this is the lowest and smallest in dimension. Seen from the western shore of the lake (ranu) Lamongan or Glagah, his right summit, which his a cone-shaped form is visible under a view angle of 9'54', and his sharp angular left summit under an angle of 7' 22' above the horizon.
After the volcanic destruction in 1931 the W foot of the mountain was harassed by heavy banjirs, which beat in pieces the bridges and covered fields with sand. The banjir problem of the Merapi was studied in detail by K.G.R. Schmidt, a separate detailed report about this is in preparation by him.
The ladumasses were deeper cut in the course of the mouths and it appears always clearer, that they were built of a heterogen, lightbrown colored sand mass, where in-between irregularly scattered, the stones occurred as individuals or as bouldertrails.
Almost all authors are the opinion, that the well - known wedusgembel, which caused death and destruction on the western slope of the Merapi, originated from the hot lava avalanches (glowing avalanches), which rolled down along the slides, whereas 'shout-out' wedusgmbel have not taken place.
In the night of May 19th to the 20th, 1919 the nature powers again have shown their everything destructing violence. The contents of the craterlake of the G.Kelut was suddenly ejected over the craterwalls.