Assertion: cave's opening | /r/CapableOf | extend below the surface
Facets:
value: on one end
type: LOCATION
Source sentences:
text: Frank Vyzralec, formerly with the State Historical Society of North Dakota, and several others investigated the site and determined that most of the hole was only a few feet deep but on one end the opening extended 7 feet below the surface and was at least 20 feet long.