[5] Following glacial dissection, renewed volcanism produced the lava dome and flow forming its summit about 170,000 years ago.

Cinder Cone, to the east of The Black Tusk, produced a 9 km (6 mi) long lava flow during the late Pleistocene or early Holocene.

The mountain currently hosts two significant glaciers, in large cirques carved into the northeastern and northwestern flanks of the broad cone below the lava pinnacle.

The Black Tusk is a member of the chain of volcanic peaks that run from southwestern British Columbia to northern California.

On the northern side of the north summit stands an isolated and intimidating rock formation known as the "Bishop's Mitre", which is rumoured to be unclimbed.