The channel belt continues after a river has dried up.
Channel belts, once hardened into rock, are made up of swaths of silt around the river. It is difficult to reconstruct details about an ancient river.
Scientists at The University of Texas at Austin are working on that front. By analyzing modern rivers they were able to come up with a rule that connects channel belts to river patterns, finding that the more channels a river has, the narrower its channel belt
The rule should hold for ancient rivers and rivers on other planets because the physics shaping them is the same over time and place.
"We can look at a river deposit from 100 million years ago on Earth or from 3.5 billion years ago on Mars and we can say something about what the actual river looked like."
The results were published in the journal geology.
The rule can help scientists see ancient rivers as well as help them understand how these rivers influenced the landscape. The surrounding floodplain can be accessed more easily by rivers with narrower channel belts.
The braided rivers are very close to the floodplain because they sit in a narrow channel belt. There could be more interaction between the river and the floodplain.
There are some things that the rule doesn't have. It doesn't hold for rivers that are kept from being able to migrate. There is a direct link between an increasing number of river channels and a narrowing channel belt when rivers are free to move. As the belt narrows, it becomes more smooth with less sharp edges.
The rule was discovered by drawing on high-resolution images and elevation data from satellites. He noticed a trend between the width of the river channel and the width of the belt on the map. He was unsure if his intuition would be right once the data was computed.
No one had looked at the relationship between river and channel-belt planform shapes in a systematic way.
More space on the channel belt is taken up by the multichannel rivers, taking up 50% or more of the belt area. A meandering river takes up as little as 1%. The ability of rivers to pick up and move debris has been boosted by this. It means that rivers can't store organic carbon on their floodplains if they want to affect sea life.
The channel belts on Mars are a reminder of the Red Planet's wet past. There are rivers of liquid methane on the moon.
They hope to use their research on rivers to learn more about the geology of other worlds.
"We will be looking to apply these metrics to other planets in our solar system and see what we can see," Goudge said.
More information: Tian Y. Dong et al, Quantitative relationships between river and channel-belt planform patterns, Geology (2022). DOI: 10.1130/G49935.1 Journal information: Geology
All Rights Reserved © 2024
