Viscosity is most affected by temperature and silica content. Basaltic magma has a low viscosity whereas rhyolitic magma has a high viscosity. Volcano - a hill or mountain formed by the extrusion of lava or ejection of rock fragments from a vent. Shield volcanoes - broad, gently sloping cones constructed of solidified lava flows. One characteristic surface of a basalt flow is called pahoehoe which has a ropy or billowy surface.
Basaltic eruptions are non-explosive .
During the 1908's, Kilauea volcano, Hawaii, was especially active. Cinder cones - a volcano constructed of loose rock fragments ejected from a central vent. Composite volcano - one constructed of alternating layers of pyroclastics and rock solidified from lava flow with slopes between those of cinder cones and shield volcanoes. Aconcagua , a composite volcano in the Andes, is 6,960 meters above sea level and the highest peak in the western hemisphere. The most viscous lavas form volcanic domes which are rich in silica.