Well, it's not exactly an explosion on the scale of Mt. St. Helens, but its still pretty cool. The USGS released two videos showing a small scale explosion in the lava lake located at the summit of Kilauea in Hawaii on Jan 8.
The explosion was caused by a small rockfall into the lava lake. Volcanoes in Hawaii are categorized as shield volcanoes and don't tend to have explosive eruptions.
Enjoy the two video clips!