Want to get an idea of what recent volcanic activity from a shield volcano looks like? Check out this video from USGS Volcanoes of Kīlauea on the Big Island of Hawaii from a mere month and a half ago of rockfall creating an explosive event!
The Medicine Lake volcano, also a shield volcano, has created all of the lava tubes and other volcanic formations we have here at Lava Beds. So when did it last erupt? The youngest flow of Medicine Lake is Glass Mountain, which is just under 1,000 years old, and within Lava Beds the youngest lava flow from Medicine Lake is the Callahan Flow, a little over 1,000 years old. Then it looked more like shield volcanoes we see today in Hawaii!