Tinakula, Solomon Islands
One of the major advantages to remote sensing is that it is very difficult to hide a volcanic eruption. Even as recently as a few hundred years ago, a major eruption could happen on the planet and there could be no written record of the event. Not so anymore (or at least it is very difficult). Case in point, this steam-and-ash plume from Tinakula (above) in the Solomon Islands - a remote location - but captured by satellite.
Image: Tinakula in the Solomon Island seen during February 2012 / NASA