The long history of volcanism at Mount Mazama, the volcano that houses Crater Lake, suggests that this volcanic center will be active in the future. Future eruptions will likely occur within the caldera and probably beneath the water's surface. The interaction of magma and water may produce explosive eruptions that send tephra and large rock fragments out of the caldera. An eruption from a vent in the caldera wall itself also might be explosive because of the abundant groundwater within the volcano. Because most of the post-caldera activity has been concentrated in the western half of the caldera, it is considered the most likely site of future activity. There is also a probability that a new, regional, volcanic vent near, but not within Crater Lake will erupt in the future.