Cinder Cone and the Fantastic Lava Beds edifice. The summit of Cinder Cone has a crater with a double rim (photo), probably created by two different phases of one eruptive period. The cone also has a widespread ash deposit identifiable for from the cone. Blocks of red, cemented scoria within the Painted Dunes lava flows (photo) are pieces of this earlier cone, which were carried away by the flowing lava. When Cinder Cone formed, the magma feeding the eruption changed composition, shifting from basaltic andesite to andesite before returning to basaltic andesite with increased titanium content. While basaltic andesites are volcanic rocks containing 53 to 57% silica,
Lava temperature, its viscosity and its mode of eruption. "Felsic" or silicic lavas such as rhyolite and dacite typically form lava spines, lava domes or "coulees" (which are thick, short lava flows) and are associated with pyroclastic (fragmental) deposits. Most silicic lava flows are extremely viscous, and typically fragment as they extrude, producing blocky autobreccias. The high viscosity and strength are the result of their chemistry, which is high in silica, aluminium, potassium, sodium, and calcium, forming a polymerized liquid rich in feldspar and quartz, and thus has a higher viscosity than other magma types. Felsic magmas can erupt at temperatures