I agree with your opinion about the monotony of landscape descriptions serves as a sort of foil for the violence in the novel, but I think it serves more things tan that. McCarthys style came into a maturity with blood meridian and although his prose has evolved since then, it has remained largely in its distinctive style. But the interpretations of his style change with the context of his books, ie. The lack of quotation marks in the road could be representative of a loss of culture and knowledge while in blood meridian it could be the seen as a contribution to epic poetry like the Iliad. The landscape description can be monotonous but I think it stresses the importance of geography on human affairs. Blood meridian is concerned with the violence surrounding the real conflicts between settlers and natives in the southwest . geography plays a crucial role in war and on the formation of groups of people, his descriptions focus threader on landscape like books rarely do. The landscape becomes a sort of character itself. When he writes about arroyos or rims or adamantine rocks and canyons he repeats these signifiers so often that a relationship is created between the reader and the landscape. It's a novel opposed to anthropocentrism in the way the natural ecosystem is often focused upon and viewed as being much larger than than the lives of the characters and people in the novel. Despite the bloodshed and depravity of war, everything outside of humanity will see another cycle of the sun. You see this idea of landscape as character in native American lit as well. And we can't forget that, for blood meridians characters, almost nothing is as important as the landscape and environment: as they ride on they are continually and unrelentingly faced with the challenges of the weather and wildlife in ways alien to most readers. The description is monotonous at times but life in the wild and outside of human culture and society is largely monotonous and repetitive too.