Note the difference in flow behavior between this and basaltic lava extruded on rocky surfaces (look up Hawaii flows on youtube for reference). Not only does the lava kinda slide along on the ice, but the thin veneer of ice that it does melt appears to pump up the volitile (gas) content of the flow, hence the bubbles and strange morphology.
Now, why doesn't all the ice melt when exposed to the lava? While this lave has a initial temperature of ~1300ºC (provided in video) and ice has a melting temperature of 0ºC, the amount of energy needed to overcome the phase change in the ice from solid to liquid is actually quite large (especially considering the volume of ice present). Add to this that as the lava flow contacts a cool surface the outside of the flow will rapidly cool, forming an insulating shell that keeps much of the heat in (this is why we get lava tube caves), which would thus further limit the amount of energy that the lava can give up.
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