Assertion: volcano's activity | /r/HasProperty | vigorous
Facets:
Source sentences:
text: Activity at steam vents in Sherman Crater, near the volcano's summit, increased in 1975 and is still vigorous, but there is no evidence that an eruption is imminent.
text: Currently, the volcano features vigorous fumarolic activity that is visible from a great distance and involves numerous vents on Materkuh.