BackgroundOjikajima is a field of monogenetic cinder cones located about 200 km behind the active volcanic front (Sudo et al., 1998). Ojika-Jima itself is a shield volcano forming a relatively flat island about 36 km2 in area, containing a variety of small peaks and pyroclastic cones ranging from 50 to 110 m in height (Sudo et al., 1998; Nakano et al., 2001). The products of this volcanic group, considered to be cogenetic, are predominantly scoria deposits and lava flows (Sudo et al., 1998). The scatter of small islands surrounding Ojika-Jima are considered part of the Ojikajima Volcanic Group as well (Sudo et al., 1998). The 1.3-1.1 Ma Uku-jima stratovolcano occupies an island to the north (Nakan et al., 2001; Sudo et al.,1998). Based on K-Ar ages (Nakano et al., 2001; Sudo et al., 1998) and the local geology, the eruptive history is divided into four stages: 1 (1.1-0.85 Ma): the most voluminous eruptive phase, with activity concentrated at the center of the field; 2 (0.85-0.7 Ma): after a possible volcanic hiatus between 0.95 and 0.76 Ma, activity resumes in the center of the field; 3 (0.7-0.56 Ma): volcanic activity expands to the adjacent eastern and western islands; 4 (0.56-0.3 Ma): volcanic activity continues but at a lower intensity (Sudo et al., 1998). Volcanism in this field is likely a result of a mantle diapir (Sudo et al., 1998).
Source: Smithsonian / GVP volcano information
See also: Sentinel hub | Landsat 8