 In addition to the lava flows, hornblende andesite can also be found near West Crater to the northwest of the Trout Creek Hill.Scientists think West Crater erupted during the Holocene epoch, about 8,000 years Before Present.Its lava flows intermix with tephra from an eruption of Mount St. Helens and tephra from the climactic eruption of Mount Mazama about 7,700 years ago.