This peninsula is referred to as the Humber Zone, a Miogeocline, the Highlands of which contain the largest external basement massif of the Grenville Orogeny in the Appalachian Orogen.

The western boundary of this inlier (along Western Brook Pond, St. Pauls Inlet, and south of Portl Creek Pond) consists of Devonian and Ordovician thrust faults, where crystalline rocks thrust over Cambrian–Ordovician carbonate rocks and the Lower Paleozoic Humber Arm Allochthon.

[4] The Tablelands, found between the towns of Trout River and Woody Point in south west of Gros Morne National Park, look more like a barren desert than traditional Newfoundland.

It is thought to originate in the Earth's mantle and was forced up from the depths during a plate collision several hundred million years ago.

Peridotite lacks some of the usual nutrients required to sustain most plant life and has a toxic quality, hence its barren appearance.

Sedimentary rocks (including some dolomitic limestone) in the southeastern sector support the North Lake association of stony sandy loam.

An association of mostly-shallow loam, the Cox's Cove, occupies a discontinuous band over shale, slate, limestone and sandstone near the coast.

The stony infertile soils of the ultramafic tablelands south of Bonne Bay belong to the Serpentine Range association.

[6] Western Brook Pond is a fresh water fjord which was carved out by glaciers during the most recent ice age from 25,000 to about 10,000 years ago.

In respect of its key role in the development of an understanding of plate tectonics, the Mohorovičić discontinuity at Gros Morne was included by the International Union of Geological Sciences (IUGS) in its assemblage of 100 'geological heritage sites' around the world in a listing published in October 2022.

[14] The interior of the park can also be accessed, notably through the multi-day Long Range Traverse between Western Brook Pond and Gros Morne Mountain.