Assertion: long valley caldera | /r/HasProperty | formed in violent volcanic eruption
Facets:
Source sentences:
text: Long Valley Caldera in eastern California (here viewed from its southwest rim toward its northeast rim on the horizon 18 miles away) was formed about 760,000 years ago in a violent volcanic eruption that blew out 150 cubic miles of magma (molten rock) from beneath the Earth's surface.