What geological feature in Gros Morne National Park is formed by the Earth's mantle being thrust upwards?

The geological feature formed by the Earth's mantle being thrust upwards in Gros Morne National Park is the Tablelands. This unique formation is primarily composed of peridotite, a rock type that originates from the Earth's mantle. The process responsible for the formation of the Tablelands involves tectonic activity, particularly the collision of tectonic plates that caused sections of the mantle to be exposed at the surface.

The Tablelands are significant because they provide a rare glimpse into deeper geological processes that are typically not visible elsewhere. The exposure of mantle rocks at the surface illustrates the dynamic nature of the Earth's crust and the geological history of the area. This feature is not only important from a geological standpoint but also contributes to the biodiversity of the park, as it supports unique ecosystems due to the different soil chemistry compared to the surrounding regions.

Other options listed do not specifically refer to this unique geological phenomenon. Plateaus, highlands, and cliffs are terms that describe different types of landforms, typically formed by erosion or sedimentary processes rather than the thrusting of the mantle. In contrast, the Tablelands uniquely symbolize the upthrust of the Earth's mantle, providing an exemplary case of tectonic geology.