Each year since the 1980 eruption of Mt. St. Helens, NASA has captured imagery of the area using one of their Landsat satellites. Over the course of those 30 years, you can watch how the earth slowly reclaims the land that was destroyed in the eruption.
You can view all of the images on their site, read about how the area was affected by the blast, and see how it’s beginning to recover:
Not surprisingly, the first noticeable recovery (late 1980s) takes place in the northwestern quadrant of the blast zone, farthest from the volcano. It is another decade (late 1990s) before the terrain east of Spirit Lake is considerably greener. By the end of the series, the only area (beyond the slopes of the mountain itself) that remains conspicuously bare at the scale of these images is the Pumice Plain.
If you want to see the imagery inside of Google Earth, you can use this KMZ file (27MB), or watch the video below which shows all of the images from 1979 through today.