In the right conditions, when magma or hot rocks encounter water hydrothermal explosions can occur. This could happen if magma encounters water from Crater Lake itself or ground water. These types of eruptions may eject large ballistic blocks (tens or more centimeters in diameter) to distances up to a few kilometers. At Crater Lake, blocks ejected at a couple hundred meters per second (typical velocity) could travel a few kilometers (a couple miles), and could easily overtop the caldera rim if the eruption vent were near the lake's shore. Hydrothermal explosions could also cause water waves on the surface of the lake up to a few meters in height, which would be very hazardous to people on the lake's surface or shorelines.