Distribution of observation points and appearance of vents. (A) Distribution of benchmarks (61 points: A0 to A60) and gravity measurement points (45 points: shown as bull's eyes). Roads are colored light gray. Triangles indicate the locations of vents B and C. (B) Appearance of vent B near point A36. This vent consists of more than one small vent. (C) Appearance of vent C near point A14. The diameter of this vent is approximately 30 cm.