<p>In images of Jezero crater on Mars, it looks like the delta fan is higher than the surrounding crater floor.</p>
<p><a href="https://i.sstatic.net/39umL.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/39umL.jpg" alt="https://www.nasa.gov/image-feature/traversing-mars-jezero-crater" /></a></p>
<p>This indeed seems to be the case with closer-up images from the Perseverance rover taken from the edge of the delta.</p>
<p><a href="https://i.sstatic.net/UatKj.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/UatKj.jpg" alt="https://www.jpl.nasa.gov/news/nasas-perseverance-sheds-more-light-on-jezero-craters-watery-past" /></a></p>
<p>Intuitively, I would guess that a river flowing would dig a kind of trench in the ground where it flows, so the ancient river bed would be lower than its surroundings. So how did the delta end up higher than its surroundings?</p>
<p>My hypothesis is that sediments were deposited, and erosion wore off the rocks around the delta, but somehow, the sediments from the delta were harder and didn't wear off as fast. Is this indeed the case, or is some other mechanism at play?</p>

CC BY-SA 4.0
2021-10-21T19:55:33.043Z
Bear in mind that, as a delta, it was emplaced under water, the crater being filled by a lake at the time.
Jean-Marie Prival
CC BY-SA 4.0
2021-10-22T10:19:01.603Z
Relevant paper: https://doi.org/10.1016/j.pss.2012.02.003
Jean-Marie Prival
CC BY-SA 4.0
2021-10-24T02:57:06.723Z
Even if not an actual delta (that is, deposited under water), alluvial fans in fairly dry regions have a similar geometry.  That is, most of the material is transported by fairly infrequent "flash flood" events, rather than by continual erosion & transport.
jamesqf
<sedimentology><rivers><erosion><mars>
Why is the delta part of Jezero crater higher than the surroundings?
usernumber
# Why is the delta part of Jezero crater higher than the surroundings?

(Asked by: username_0 on 2021-10-21)

In images of Jezero crater on Mars, it looks like the delta fan is higher than the surrounding crater floor.

[![https://www.nasa.gov/image-feature/traversing-mars-jezero-crater](https://i.sstatic.net/39umL.jpg)](https://i.sstatic.net/39umL.jpg)

This indeed seems to be the case with closer-up images from the Perseverance rover taken from the edge of the delta.

[![https://www.jpl.nasa.gov/news/nasas-perseverance-sheds-more-light-on-jezero-craters-watery-past](https://i.sstatic.net/UatKj.jpg)](https://i.sstatic.net/UatKj.jpg)

Intuitively, I would guess that a river flowing would dig a kind of trench in the ground where it flows, so the ancient river bed would be lower than its surroundings. So how did the delta end up higher than its surroundings?

My hypothesis is that sediments were deposited, and erosion wore off the rocks around the delta, but somehow, the sediments from the delta were harder and didn't wear off as fast. Is this indeed the case, or is some other mechanism at play?

**Tags:** sedimentology, rivers, erosion, mars

> **Comments:**
> **username_1**: Bear in mind that, as a delta, it was emplaced under water, the crater being filled by a lake at the time.  
> **username_1**: Relevant paper: https://doi.org/10.1016/j.pss.2012.02.003  
> **username_2**: Even if not an actual delta (that is, deposited under water), alluvial fans in fairly dry regions have a similar geometry.  That is, most of the material is transported by fairly infrequent "flash flood" events, rather than by continual erosion & transport.  

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## 0 answers

