Characteristics of tephra from cinder cone,Lassen volcanic National Park,California

Cinder Cone, an undissected, 200 m high Holocene cone in Lassen Volcanic National Park, California, is mantled by basaltic blocks and bombs, including abundant large spherical accretionary bombs. Types of pyroclasts, ranging from light brown sideromelane droplets to blocky, crystalline tachylite fragments, appear to reflect the vent history; when the vent was clear, an abundance of lava was erupted at higher temperature and lower viscosity, producing predominantly rapidly chilled sideromelane droplets. When the vent was blocked by pooling of lava or by slumping of talus from crater walls, intermittent Strombolian eruptions ejected more viscous, crystalline to tachylitic fragments and comminuted talus. Such activity has been observed at Mt. Etna, Italy and Heimaey, Iceland. Avalanching of debris into the crater and down outer slopes, one of the main processes in cinder cone formation, isalso responsible for thevarieties of pyroclast types formed during Strombolian eruptions.