Three well-known volcanic and geothermal sites in the northwestern part of the Ring of Fire—Mount Fuji, Changbaishan, and the Valley of Geysers in Kamchatka—occupy very different positions within the geometrical framework considered here.
and the locations of Changbaishan, Mount Fuji, and the Valley of Geysers.
In the accompanying map, the inner and outer boundaries of the Ring of Fire are shown in red, while the calculated mantle-convection-roll divisions are shown as black lines.
Changbaishan is located close to the outer boundary of the Ring of Fire. At the same time, it lies within the region where the proposed Indian Ocean Ring overlaps the Pacific Ring. Its position can therefore be examined in relation to the interaction between two large-scale tectonic systems rather than to the Pacific Ring alone.
Mount Fuji, by contrast, is situated close to a calculated division between two large-scale lower-mantle convection rolls. It also marks the northern end of the Izu–Bonin subduction system, which follows this calculated mantle division southwards. Fuji therefore provides a particularly clear example of a volcanic centre associated directly with the geometry of the mantle convection roll system.
The Valley of Geysers in Kamchatka occupies yet another type of position. It lies close to the inner boundary of the Ring of Fire and also near a major N–S axis that can be regarded as an extension of the minor axis of the Antarctic ellipse.
This same meridional direction continues through the longitude of the Geysir geothermal area in Iceland. When viewed relative to the geographic poles, the Iceland–Kamchatka direction forms an approximately 90° relationship with Yellowstone. The three major geyser regions therefore occupy geometrically related positions within the broader global framework, although the immediate tectonic setting of each is different.
These three examples illustrate an important point. Exceptional volcanic or geothermal activity need not correspond to only one kind of geometrical relationship. In this case:
- Changbaishan is associated with the overlap of two proposed tectonic rings;
- Mount Fuji is associated with a major lower-mantle convection-roll division and the beginning of the Izu–Bonin subduction system;
- the Valley of Geysers is associated with the inner boundary of the Ring of Fire and a major meridional axis linked geometrically with Antarctica.
The locations can therefore be examined as different surface expressions of the same broader tectonic framework.
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