By Stephen Hill and Amanda Fischer. Stephen wrote the text and Amanda provided the images.
The geology you can see from an airplane is truly spectacular- the sights of the world below have enchanted most everyone who has taken an airplane. In this post, we walk you through the geology behind some of the sights you might see from the skies going across the western United States. Next time you take a flight, look out the window and learn more about the geology all around us!
Most people are aware that there are volcanoes in the western United States (U.S.) thanks to the frequent headlines of some of the large strato-volcanoes (e.g., more cone-shaped volcanoes, like Mt. Saint Helens) in the Cascades of Washington and of course the “doomsday” headline-maker, the Yellowstone caldera or “super-volcano.” What many folks are not aware of are the many smaller volcanic fields that dot the South-Western U.S. including Arizona and New Mexico, even though they are often responsible for some of the iconic mesas and plateaus associated with those states. The 8,000 square mile (about the area of Vermont) Raton-Clayton Volcanic Field of New Mexico is one such example.
The first occurrence of volcanism at the Raton-Clayton Volcanic Field in New Mexico is thought to have occurred around 50 million years ago and has had sporadic eruption events to as recent as 30,000 years ago. Image 1 was taken while flying over this volcanic field. Visible in the center of the frame is a textbook example of what geoscientists call a cinder cone (or scoria cone) volcano: this one in particular is called Capulin Volcano. Cinder cones are the most common type of intraplate volcano (i.e., a volcano not located on the boundary of a tectonic plate) and are formed when fountains of lava erupt from a volcanic vent. As the lava is ejected into the air, it cools into rock and ash and begins to collect around the vent. Over a period of constant or spaced-out eruptions, this accumulation will form the cone shape you see. Capulin represents some of the younger activity in the field, estimated to be 30,000 years old which is why it retains its textbook shape–– it hasn’t yet been weathered away, like some of the older features of the field.
The older a feature is, the more time it has spent exposed to the weathering processes of Earth’s surface; this can drastically alter the way some volcanic features look. If we look at Image 2, we can see an expanded view of Image 1. Now, a second cinder cone is visible at the bottom of the frame. In between the two cinder cones, we can see two features that look like squiggly outlines with flat tops. These are called mesas now, and they’ve been worn down over many, many years of weathering and erosion, primarily from wind and rain.
Weathering and erosion are also responsible for some of the most spectacular aerial scenery you will see over the Western US (e.g., the Grand Canyon). Visible in Image 3 is Glen Canyon, which, just like the Grand Canyon, has been cut by the mighty waters of the Colorado River. The geology of this area is primarily dominated by sandstone (i.e., Navajo & Wingate sandstones) which have been eroded by the flow of the river over the course of millions of years. The meanders of the river are cut into the sandstones and leave traces of the river’s path from years gone by: this produces many spectacular views. Viewing erosive patterns from a bird’s eye view can also help inquisitive minds better understand runoff and the creation of rivers/watersheds, as seen in Image 4.