Sitting beneath Mt St Helens is Spirit Lake. It was there before the blast but not exactly where it is now. The debris that rushed off the mountain and the side of the volcano collapsed pushed down to the lake and actually raised it up a couple of hundred feet. The water also rushed up the surrounding hills. These had been covered in trees which, as the blast expanded outwards, got snapped off at their bases. These stripped tree trunks got picked up by the water and washed back in to the lake as the water retreated. The result is that there are now thousands of tree trunks floating on the surface of the lake making a raft. This moves with the wind so its location on the lake surface changes all the time but it always covers a substantial portion of the lake.
The lake also covers the previous location of a lodge that used to serve visitors. The owner of the lodge died in the explosion and the raised level of the lake now puts it above the lodge’s original location. The owner had been advised to leave but he had lived there all his life and he wasn’t interested in going. He was one of the many people to die that day.