Mayon is a volcano in the Philippines that has been rumbling quite a bit lately, and scientists think it may be on the verge of a catastrophic eruption. They've issued a Level 4 alert; the only higher alert is Level 5, which is when a volcano is actually and actively erupting. This is serious: 45,000 people have been evacuated in case the volcano blows. This image of Mayon was taken last week and posted on the Earth Observatory Image of the Day:
As you can see, downslope of the volcano -- and in the path of previous flows -- is the town of Legazpi, with nearly 200,000 inhabitants. Scientists at the Philippine Institute of Volcanology and Seismology are recommending making danger zones that extend for several kilometers north and south of the volcano.
Activity such as earthquakes and smaller eruptions have already been seen, and it looks like this volcano ...