The Reykjanes Ridge can be extended over Iceland (red line), explaining the location of several geothermal spa sites in Iceland.
The red line shows the Reykjanes Ridge and how the two relevant convection rolls extend over iceland. Over the division line, or close to it, the Blue Lagoon at Svartsengi, Krauma of Deildartunga, and Geosea of Skjálfandi Bay, near Húsavík are found.
The blue line is actually the main division line of the two large convection rolls in lower mantle, but the upper most small convection rolls converge against each other. The division line marks the eastern edge of the West Volcanic Zone, where Fontana at Laugarvatn is located, and Nature Baths of Mývatn. It is also close to the Geysir area and Hveravellir in the center of Iceland. The Reykjadalur geothermal river has many bathing sites, near Hveragerði, which is of course on the blue line. Therefore, some additional points could be added with explanations according to the mantle currents pattern underneath. It is not necessary, though, because this shows the main pattern.
This shows the resemblance between convection rolls of the mantle and the main geothermal spa areas in Iceland.
Here is a list of web sites for those spa sites.
Krauma – at Deildartunga in Borgarfjörður area, West Iceland:
Geosea – at Húsavík í NE Iceland:
Fontana – at Laugarvatn, South Iceland:
Blue Lagoon – at Svartsengi on the Reykjanes Peninsula:
Nature Baths – at Mývatn in NE Iceland:
Reykjadalur River – at Hveragerði in Ölfus district, South Iceland:
Hveravellir – NE of Langjökull in Central Iceland