I love it when I read something that completely alters my worldview. “The origin of mud” by Laura Poppick in Knowable Magazine is just such an article. The title alone intrigued me. I can’t say I’ve ever put much thought into mud unless I’m muttering about it covering my shoes.
It turns out that mud has done much to shape our planet. According to the article, 460 million years ago there were no plants on earth. Because of that, most sediment on land would quickly enter rivers and wash out to sea during storms. We know this because there are lots of fossilized fish from that timeframe, all around the world, that seem to have been choked by catastrophic mudslides. Also, this rapid movement of mud to the sea floor indicates that land consisted of barren rock.
Once plants appeared, things changed. Upon their arrival, there is evidence of 10 times as much mud on land, because roots and stems hold mud in place. That mud, in turn, shaped continents. Plants also reduce flooding and increase the production of mud, because their roots break down rocks into the sediment that is the primary ingredient thereof.
Before plants, most rivers were braided like the one depicted in the artistic textile below. (That photo was taken by my husband on our trip to Denali National Park a year ago.) As you can see, with no plants to hold the riverbanks in place, they’re constantly collapsing and reforming based on the depth and strength of the water flow.
After plants, and the mud that could then cling to the riverbanks, most rivers formed single channels. Yes, they might curve and meander and form oxbows, or they could also be rather straight, but they tended to remain stable and predictable. And bendy vs. straight rivers alter the water’s chemistry and speed, and therefor create a variety of ecosystems.
Animals also had to evolve to be able to travel through the increased mud on land, developing new body parts. Some animals ate the mud particles and produced muddy feces. And loosening up that mud helped to disburse it into floodplains.
I’ll summarize with a quote from the article:
“Life has always congregated around rivers, from the very first emergence of plants and animals onto land. That’s why the early accumulations of mud alongside rivers — and how mud influenced their flow — is nothing to throw dirt on.”