Abstract
Abstract A detailed magnetic survey, based on 1018 stations, was conducted in the Usu volcanic region, Hokkaido, Japan. From the study, the following results were obtained: (1) The main body of Usu volcano is composed of strongly magnetized basaltic somma lavas and weakly magnetized crater fill. (2) The southern rim of somma volcano is situated about 200 m south of the present topographic rim, suggesting the existence of the buried horseshoe-shaped caldera which is thought to have been formed several thousand years ago. (3) Parts of the Mt. Showa-Shinzan lava dome formed in the 1943–1945 activity are still occupied with lavas of high temperature, above the Curie temperature of the ferromagnetic minerals. (4) The root of the lave dome of Mt. Showa-Shinzan has almost the same diameter as that of the dome exposed on the earth's surface. (5) An intrusive body about 200 m in diameter may exist at shallow depth in the Roof Mountain of Mt. Showa-Shinzan.
Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
