Plunging into sudden fog edges can cause disorientation and accidents. Fortunately, neither happened here. On an already cool, damp day, it takes very little extra moisture to obscure the field of view. The source was a natural steam vent in the Gunnuhver geothermal area in Iceland, just a few miles from and nearly a decade before the series of fissure eruptions in the early/mid 2020s near Grindavik. Under a shallow thermal inversion, the well-defined plume of effluent wafted a considerable distance across the land to create this extraordinary visibility gradient at the surface. This doesn’t fit the commonly known fog types: radiation, advection, or precipitation. Instead it is directly generated by release of underground heat and moisture–geothermal “steam” fog.
