The US Geological Survey produces maps that are works of art, as well as highly informative cartography. Meticulously hand drawn by artists, many of these maps can be appreciated for their visual appeal, even if you don’t delve too deeply into the details of rock units, faults and folds. One of my all-time favorites is the Geologic Map of the United States published in 1974.

This colorful geologic map adorned a wall of my office for many years, where I could appreciate the aesthetics of the map, as well as the information it conveyed. Our vast country has many regions with interesting geology, appealingly arrayed in vibrant colors on this great map – a few of my favorite areas (especially one with “caterpillars”) are described below.

Geologic Map of the United States , 1974, by: Philip Burke KingHelen M. Beikman, and Gertrude J. Edmonston

An excellent blog post about the US geologic map is published on a website I recently discovered by geologist Marli Miller, a University of Oregon instructor. In her post she provides helpful descriptions about how to read a geologic map and recognize the standard abbreviations and map colors for geologic time periods. (Map art is enhanced by a color scheme standardized by the USGS and that follows the rainbow of colors in a spectrum: in order of increasing age, younger Tertiary rocks have map units of oranges and yellows, Mesozoic rocks have map units in greens, with older Paleozoic rocks in blue and indigo. On the US map you can clearly see lots of blue tones [= older rocks] in the eastern US.) If you scroll down to “The Maps” section of Marli Miller’s post, there are descriptions about the geology of specific regions. Check out her post here:

Geologic Map of the United States showing map regions that Marli Miller describes in more detail in her blog post

Detailed Maps

My favorite of the areas highlighted is Map 2 (below) with the army of colorful “caterpillar” mountain ranges marching across the Basin and Range province.  Whenever I drive through this region, extending through Nevada and into Utah, I admire the contrasts between the high and rugged mountain ranges and the vast flat and empty valleys. Driving the arrow-straight highways from west to east, I think the landscape becomes even more beautiful as each uplift in the long succession of mountain ranges is crossed. And looking out over the huge expanse of emptiness always soothes my soul.

Map 2. Basin and Range Province Geology

Map 2. Geology of the Basin and Range Province — mountains are shown by the bright colors  representing older rocks and basins (valleys) are light in color with young alluvial sediments

I also like Map 3 and the description of the Colorado Plateau and features of the Grand Canyon (Map 3a). Peering across this massive slice into the Earth, catching glimpses of the thin ribbon of river winding below, and admiring the varied rock units arrayed along the canyon edges, is something I hope to do many more times during my life.

Full disclosure here: I think western US geology is far more interesting than central or eastern US geology. However, I will admit I have a fondness for the Black Hills in South Dakota (Map 4), where I spent several weeks in a geology field camp a few decades ago. And although the Appalachians are only eroded remnants, and thus mere shadows, of the mighty mountain range that formed over 400 million years ago, that geology is  notable also (Map 5). (Plus, I like the blue tones on the map.)

There are many other fascinating geologic topics, plus fabulous photographs, in Marli Miller’s blog (see ). I’ll probably refer to more of them in my future posts – and you might want to look at some also. I’d love to hear if there is a stretch of territory shown on the US geologic map that is especially intriguing to you, and why you like it. I have a hunch about why we prefer certain areas over others, and I’m curious to see whether that holds up, since I have readers that live across the US and even into Canada. Please scroll down to the end of this web page and post your comments – thank you!

A view from the North Rim of the Grand Canyon (my photo)