Quantitative observations of an eruption in far-eastern Russia show that two different kinds of lava, 'a'a and pahoehoe, interact with the snow cover in very different ways, reports a study published this week in Nature Communications. Understanding how volcanoes in cold regions interact with snow and ice is vital for hazard mitigation and flood damage prevention.

Benjamin Edwards and colleagues witnessed an eruption on the Kamchatka Peninsula and observed lavas moving on top of, beneath and through fractures in the snow. They were able to dig observation pits in front of the advancing lava flows to identify how lava moved through the snow and how much melting was happening at the lava-snow interface. They found that blocky 'a'a lavas advanced on top of the snowpack with melt water accumulating beneath the lava flow, whereas smooth flowing pahoehoe lavas advanced under or inside the snowpack, allowing melt water to interact with the lava and producing distinctive lava textures.

Although the observed volcano is remote, these findings could be important for investigating the possible hazards of ice-clad volcanoes in more populated areas; glacial floods have been identified as the most frequently occurring volcanic-related hazard in Iceland. The authors also suggest that their findings will help to identify ancient lava-ice interactions on Earth, where retreating snow-lines may indicate periods of climate warming, and on Mars, where regions of volcano-fluid interaction may have harboured life.