At the Mountains of Madness exemplifies what would become known as Lovecraftian horror. This genre of horror relies strongly on the idea that true horror is unknowable, indescribable, and incomprehensible. The very setting of the story is significant in this respect, since Antarctica’s climate makes it one of the least explored—and therefore least known or knowable—regions of the Earth. The supernatural elements of the novel build on this premise. Lake struggles to tell whether the Old Ones are plant or animal, which suggests that their existence defies the narrow intellectual categories into which he tries to place everything. Likewise, the Shoggoths’ shifting shape terrifies Dyer because he can never truly know or understand it. Encountering the unknowable traumatizes Danforth even more obviously, as the vision he experiences on the plane ride back from the Old Ones’ city causes him to have a nervous breakdown.

Dyer’s frequent proclamations that he cannot truly describe the horrific sights he has experienced provide useful context for Danforth’s reaction. Language is in part a way to make sense of the world. Because Dyer lacks the words to explain or even recount events so far removed from normal human experience, the events themselves necessarily remain senseless.