<Tr> <Th> Easiest route </Th> <Td> Road </Td> </Tr> <P> Lava Butte is a cinder cone in central Oregon, United States, just west of US Highway 97 between the towns of Bend, Oregon, and Sunriver, Oregon . It is part of a system of small cinder cones on the northwest flank of Newberry Volcano, a massive shield volcano which rises to the southeast . The cinder cone is capped by a crater which extends about 60 feet (20 m) deep beneath its south rim, and 160 feet (50 m) deep from the 5,020 - foot (1,530 m) summit on its north side . Lava Butte is part of the Newberry National Volcanic Monument . </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> <P> The early history of Lava Butte is not known, but it is assumed that Native Americans observed the eruptions and later ascended the prominent new landmark . White settlers arriving in the 1800s also noted the landmark . In 1903, I.C. Russell was the first geologist to study the butte and speculated that it erupted as recently as 150 years ago . Dr. Howel Williams estimated it to be much older, but incorrectly at 1,000 years old . In September 1914, Lava Butte "erupted" when the Bend Chamber of Commerce simulated an eruption to surprise a visiting Portland group . In 1925, USGS geologist Harold Stearns studied the Newberry area and recognized the fissure system which extends from Lava Butte to East Lake within Newberry Caldera . </P>

When was the last time lava butte erupted