When I see a geological map, it doesn’t make a whole of of sense to me. Perhaps that helps me appreciate their abstract beauty. The fact that they are in fact not at all abstract, and represent the very ground we stand on, makes them that much more appealing to me.
Recently I’ve had the opportunity to look at a lot of these maps. I have learned a little bit about geology, but I have also learned to appreciate the sheer visual quality of these works of art.
One striking example is this snapshot from the USGS geological map of Virginia, showing a portion of the Appalachian mountains:
If you’re a geologist, then you’ll know that greens and blues tend to represent sedimentary rocks, whereas purples are for metamorphic rocks. If you’re a geological rube like me, you’ll see an interesting composition with a clear northeast/southwest slant, which presumably tells us something about the formation of this place. The northwest half of the picture looks like billows of smoke, perhaps because the Great Smoky Mountain National Park is not far.
This color scheme is soft and soothing. The Appalachian mountains are old and tired, and they are slowly eroding away. But in northern California, where volcanic processes are still very much alive, the picture looks rather different:
This is the land of earthquakes, hot springs and active volcanoes. Red is the dominant color. The deep red represents rock that has come out of the bowels of the earth as magma. The lighter red shows areas of diorite, an extremely hard rock that was highly prized in ancient times. Around here, things are still moving, and are never at rest.
Sometimes the old and the new can mix, like in central Colorado, where we can see just about every color on the palette:
Here the Great Plains meet the Rocky Mountains (Denver is just off the upper right corner). This picture seems almost random, as if an artist had simply thrown paint blobs at a canvas. Things have been churned around quite a bit, and there is no clear picture — just an image of chaos.
Other regions are more organized, and sometimes even tortured, such as this area of western Massachusetts:
Most of the rocks here are quite old, a billion years and more, and have been worked and reworked by geological processes. Their shape reminds me of a pastry crust, folded and refolded until the layers can no longer be counted. This is busy, worried, anxious.
A more soothing image can be found in central North Carolina:
The general impression is much calmer, friendlier, with colors that seem almost bubble-gummy. Here the plains of the Atlantic coast rise slowly to meet the mountains. There are no volcanoes anywhere, and earthquakes are uncommon. This seems like a relaxed, genteel place.
I will end with one of my favorite places in the world: the Cascade mountains. They are young and vigorous. They are still growing. And yet…
If you look carefully, you’ll see a certain amount of veining. These are the mountains eroding away. Even though they are young, the weather is already working on them. It rains a lot on these slopes, and the water trickling down carries with it bits of rock. Yes, even the mighty Cascades are being worn down by drops of water. There is probably some philosophical lesson in there somewhere, but I will leave that to you, gentle reader.
All screenshots in this article are from our series of iPhone GIS apps. Many thanks to Dr. Janine Weber for her gracious assistance with geological concepts.