Although basaltic lava flows are the most common eruptive activity in the Lassen volcanic center, they could also produce more violent and thus more hazardous silicic lava flows, in addition to building additional, unstable lava domes that could collapse and spawn pyroclastic flows that could extend for several miles. Because Lassen Peak has a significant amount of snow and ice, these pyroclastic flows (or hot volcanic ash) might mix with water to form lahars (volcanically induced mudslides, landslides, and debris flows) that could destroy nearby communities. Dacitic eruptions could produce volcanic columns of gas and ash that could threaten aircraft in the area. Moreover, the Lassen volcanic center poses threats to visitors from sudden avalanches that could be entirely unrelated to eruptive activity. Due to the threat of an avalanche from nearby Chaos Crag if volcanic activity renewed in the area or an earthquake occurred, the Visitor Center for Lassen Peak located at Manzanita Lake closed in 1974. In 1993, a rockfall with a volume of fell down Lassen Peak's northeastern flank, but no visitors were harmed. Despite the volcano's current quiet state, rockfalls still pose significant hazards due to the peak's inherent instability.