The Nash Crater cinder cone erupted lava flows about 3,850 years ago, which coursed west and blocked a stream to create Fish Lake and Lava Lake. The lava flows were unvegetated and blocky. According to Sherrod et al. (2004), these flows, also known as the Fish Lake lava flow, represent the oldest lava flows near the Santiam and McKenzie Passes after the cataclysmic eruption of Mount Mazama. Radiocarbon dating of a charred conifer branch found in Sand Mountain volcanic ash yielded an age of 3,440 ± 250 years Before Present (BP). Radiocarbon dating of charcoal on a lateral moraine near Nash Crater gave an age of 2,590 ± 150 BP. The Lost Lake cinder cones erupted about 1,950 years ago, along a fissure that trended from north to south near the northern end of the volcanic field. These eruptions blocked the Lost Creek tributary, forming Lost Lake.