<P> Like the other cinder cones in the area , Lava Butte only experienced a single eruption , dated by geologists in 1977 to 6,150 carbon - 14 years , equivalent to about 7,000 years ago . The eruption began with a fissure spewing hot cinders to form the cone . In the next phase , a river of hot basalt flowed from the base of the small volcano to cover a large area to the west with a lava flow which remains largely free of vegetation . The lava flows reached the Deschutes River about 2.5 miles ( 4.0 km ) to the west of the cone , burying its former channel under over 100 feet ( 30 m ) of lava and damming the river to form a lake , known as Lake Benham . The river eventually overflowed the lava dam and eroded down into it , draining the lake and forming Benham Falls . Geologists estimate that 90 % of the magma erupted as lava flows , 9 % as scoria which forms the cone , and 1 % as volcanic ash which forms a thin layer extending to the north . </P>
<P> Like the other cinder cones in the area , Lava Butte only experienced a single eruption , dated by geologists in 1977 to 6,150 carbon - 14 years , equivalent to about 7,000 years ago . The eruption began with a fissure spewing hot cinders to form the cone . In the next phase , a river of hot basalt flowed from the base of the small volcano to cover a large area to the west with a lava flow which remains largely free of vegetation . The lava flows reached the Deschutes River about 2.5 miles ( 4.0 km ) to the west of the cone , burying its former channel under over 100 feet ( 30 m ) of lava and damming the river to form a lake , known as Lake Benham . The river eventually overflowed the lava dam and eroded down into it , draining the lake and forming Benham Falls . Geologists estimate that 90 % of the magma erupted as lava flows , 9 % as scoria which forms the cone , and 1 % as volcanic ash which forms a thin layer extending to the north . </P>
when was the last time lava butte erupted
when was the last time lava butte erupted
6,150 carbon - 14 years , equivalent to about 7,000 years ago
6,150 carbon - 14 years , equivalent to about 7,000 years ago