Assertion: volcano's magma | /r/HasProperty | viscous
Facets:
value: very
type: DEGREE
value: because of its high silica content
type: CAUSE
Source sentences:
text: The volcanoes form steep cones, rather than rounded shapes, because the magma is viscous.
text: This magma tends to be extremely viscous because of its high silica content, so it often does not attain the surface but cools and solidifies at depth.
text: Volcanoes related to converging plate margins (see the section Volcanism and tectonic activity) generally have a high gas content, and their magma is very viscous.