In 2013, a storm hit Colorado’s Front Range area that set a number of records. In a matter of 5 days, the area received about a year’s worth of normal rainfall, between 7 and 18 inches in most parts of Boulder and Larimer counties. The storm caused mudslides, landslides, and massive flooding. And in those five days, it caused as much erosion as the area would normally see in about 1,000 years.
Erosion is a constant force that eats away at mountains, hills, and the like, moving soil and rock from one place to another. It’s responsible for creating all kinds of interesting geological formations, and keeps the Earth’s surface constantly changing, if only be tiny increments. Normally, long-term erosion in the Boulder area removes about two-tenths of an inch of sediment every century, which is less than the width of a human hair each year. In a given year, the weathering of stones helps to create almost as much sediment.
Studying erosion can, therefore, be difficult because it can be hard to see how it works in real time. Events like the storm of 2013 help us to understand more about erosion and its impact on geology. But those storms only come around once every century or millennia, so we can’t really rely upon them. That storm, for example, caused 120 separate landslides, which removed anywhere from 350 to 740,000 cubic feet of sediment. Even the smallest of those landslides moved more sediment than centuries of normal erosion.
The 2013 storm gave us a lot of very interesting information, which a research team from the University of Colorado at Boulder has written about in a new study, which was recently published in the journal Geology. This research helps us to better understand how erosion works over time. It seems that periodic bursts of activity are essential to the sculpting of geological features, in addition to normal, daily erosion.