Description Cinder Cone and the Fantastic Lava Beds

cinder cone in lassen volcanic national park.



false-color aerial photo of cinder cone , fantastic lava beds



the crater of cinder cone 1,000 ft (300 m) in diameter , 230 ft (70 m) deep.

cinder cone 700 ft (213 m) high cone of loose scoria. scoria forms when blobs of gas-charged lava thrown air during eruption , cool in flight, falling dark volcanic rock containing cavities created trapped gas bubbles. summit of cinder cone has crater double rim (photo), created fluctuating eruptive activity late in formation. cone has several associated blocky lava flows, , related, widespread ash deposit identifiable 8 10 miles (13 16 km) cone. there 2 scoria cones @ cinder cone—the remnants of buried earlier cone can seen on larger cone s south side. of earlier cone destroyed lava flows erupting base. blocks of red, cemented scoria within painted dunes lava flows (photo) pieces of earlier cone, carried away flowing lava.

during formation, composition of molten rock (magma) feeding eruption changed basaltic andesite andesite , basaltic andesite, higher titanium content. chemically, basaltic andesites volcanic rocks containing 53 57% silica (sio2), , andesites containing 57 63% silica. though chemically distinct, lava flows , scorias @ cinder cone similar in appearance. dark, fine-grained rocks, containing few visible crystals of minerals olivine, plagioclase, , quartz.

the earlier erupted group of volcanic deposits @ cinder cone, relatively titanium-poor, consist of older scoria cone, old bench flow, 2 painted dunes flows, , lower part of widespread ash layer. later erupted, relatively titanium-rich group consists of large, younger scoria cone, upper part of ash layer, , 2 fantastic lava beds flows. flow 2 of fantastic lava beds (see geologic map) flow diller thought had been erupted in 1851. ash on old bench , painted dunes lava flows brightly oxidized because fell on lava flows when still hot. oxidized ash belongs same compositional group fantastic lava beds flows, last flows erupted @ cinder cone. volcanic materials @ cinder cone therefore represent single eruptive sequence spanned no more few months.

an unusual characteristic of fantastic lava beds presence of anomalous quartz crystal xenocrysts (foreign bodies in igneous rock). geologists think picked wall rocks lava moved toward surface. lava , pyroclastics of cinder cone , fantastic lava beds made of basaltic andesite andesite.