The mountain consists of a narrow north-south trending ridge of fine-grained volcanic rock and small amounts of fragmental material.

[6] Stratovolcanoes can reach heights of 2,500 m (8,000 ft) and consist of alternating layers of lava flows, volcanic ash, cinders, blocks and bombs.

The removal of the ejected volcanic material has exposed the dacite lava that forms the narrow north-south trending ridge of Mount Fee.

[6] The Black Tusk, a pinnacle of dark volcanic rock to the southeast, is also interpreted to be the remains of a deeply eroded volcano that was once covered with pyroclastic material.

Its volcanic rocks remain undated, but the large amount of dissection and evidence of glacial ice overriding the volcano indicates that it formed more than 75,000 years ago before the Wisconsinan Glaciation.

[1] However, a large variety of volcanoes formed subglacially between 25,000 and 10,000 years ago in the vicinity of Mount Fee, including the lava domes of Ember Ridge to the south.

The conduit from which these lava flows originated was likely vertical in structure and intruded through older rocks deposited during Fee's earlier volcanic events.

Extensive erosion following the last volcanic event at Mount Fee has created the rugged north-south trending ridge that currently forms a prominent landmark.

Glassy volcanic rocks, such as rhyodacite, were widely used to make knives, chisels, adzes and other sharp tools before the arrival of Europeans in the 18th century.

[2] Like other volcanoes in the Garibaldi Belt, Mount Fee is not monitored closely enough by the Geological Survey of Canada to ascertain how active its magma chamber is.

[12] A significant eruption at Mount Fee would probably have considerable effects, particularly in a region like southwestern British Columbia where the Garibaldi Belt is located in a highly populated area.

[4][12] Because of these concerns, significant support from Canadian university scientists has resulted in the construction of a baseline of knowledge on the state of the Garibaldi volcanoes.