Assertion: sheer cliff | /r/HasProperty | ascended at fracture zones
Facets:
value: on sand dunes
type: LOCATION
Source sentences:
text: Along canyons and at their boxlike heads it forms vertical or even undercut walls-sheer cliffs 400 to 600 feet high that can be ascended only at fracture zones or on sand dunes that extend from the bottom to the rim.