Villarrica volcano is one of the most active volcanoes in the Chilean Andes. A colleague of mine (Esteban Alonso) told me that last week he went ski touring up there and when he reached the summit he could see the bubbling lava in the bottom of the crater, and could even feel its heat... Sentinel-2 also feels the heat! The lava in the crater is warm enough to emit shortwave infrared radiation: The situation in the crater remains quite stable all over the year in contrast to the snow cover, as shown in this time series of cloud-free images from Sep 2016 to Sep 2017:
It's also visible in the thermal band (near 11 µm) of Landsat-8 despite its lower resolution of ~100m (image below acquired on 2017-05-09). Related links: Villarrica Volcano, Chile on ESA website.Hot N Cold by Katy Perry.