What material found in magma is formed from the elements oxygen and silicon?

Silica is the correct answer because it is a chemical compound composed of silicon and oxygen, which are two of the most abundant elements in the Earth's crust. In magma, silica plays a crucial role in determining the properties of the resulting igneous rocks. The presence of silica influences the viscosity of magma, which in turn affects the type of eruption and the characteristics of the volcanic rock that forms.

Basalt, granite, and obsidian are all types of igneous rocks that contain varying amounts of silica, but they are not purely composed of the elements oxygen and silicon. Basalt is considered a mafic rock that contains lower silica content, while granite is a felsic rock rich in silica. Obsidian is a volcanic glass that also has a high silica content, yet it is ultimately composed of a range of minerals rather than just silica itself. Thus, silica distinctly represents the specific combination of the two elements oxygen and silicon found in magma.