Watching lava fight with snow in Kamchatka:
You might guess that these red-hot lavas would burn through the snow almost instantly, reducing the surroundings to slush and steam. However, you’d be wrong. The ʻaʻa lava flows actually produced surprisingly little melt, though the snow beneath them would be gone in less than 24 hours. That’s partly because the blocky crust armoring the underside of the flow (at a cool 900 °C) insulates the snow from the hotter core of the lava. But it’s also because the snow, which contains so much air space, is a poor conductor of heat.Pretty
The pahoehoe flows were a different matter. Rather than rolling along atop the snow, they pushed down into it, producing some wild stuff— plowing up fractured blocks of snow, and even inflating domes beneath the surface that would then melt the snow above. This interaction produced more meltwater, which seeped through the snow and transferred heat much more effectively than the lava could do alone.
Even so, these flows were moving pretty slowly, and while the pahoehoe flows could produce some streams and small outbursts of meltwater, it wasn’t nearly enough to generate the kinds of dangerous mudflows common for more explosive eruptions.
Count this as stuff that Ted sends.
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