Some features of this site are not compatible with your browser. Install Opera Mini to better experience this site.

Earth Matters

February 2018 Puzzler

February 20th, 2018 by Adam Voiland

Every month on Earth Matters, we offer a puzzling satellite image. The February 2018 puzzler is above. Your challenge is to use the comments section to tell us what we are looking at, when the image was acquired, and why the scene is interesting.

How to answer. You can use a few words or several paragraphs. You might simply tell us the location. Or you can dig deeper and explain what satellite and instrument produced the image, what spectral bands were used to create it, or what is compelling about some obscure feature in the image. If you think something is interesting or noteworthy, tell us about it.

The prize. We can’t offer prize money or a trip to Mars, but we can promise you credit and glory. Well, maybe just credit. Roughly one week after a puzzler image appears on this blog, we will post an annotated and captioned version as our Image of the Day. After we post the answer, we will acknowledge the first person to correctly identify the image at the bottom of this blog post. We also may recognize readers who offer the most interesting tidbits of information about the geological, meteorological, or human processes that have shaped the landscape. Please include your preferred name or alias with your comment. If you work for or attend an institution that you would like to recognize, please mention that as well.

Recent winners. If you’ve won the puzzler in the past few months or if you work in geospatial imaging, please hold your answer for at least a day to give less experienced readers a chance to play.

Releasing Comments. Savvy readers have solved some puzzlers after a few minutes. To give more people a chance to play, we may wait between 24 to 48 hours before posting comments.

Good luck!

Answer: The image above shows a new reservoir near the confluence of the Sesan and Srepok Rivers in Cambodia. Mike Walker was the first to get the correct location. Read more about the image in our February 24, 2018, Image of the Day.

12 Responses to “February 2018 Puzzler”

  1. Akshinthala Prasad says:

    Algae bloom in inland waters
    I think the image shows the massive single-celled algae, also known as phytoplankton with their chlorophyll a pigment in a river and its tributaries, that are greatly impacted by anthropogenous activities. High nutrients trigger the explosive growth of phytoplankton. I am not familiar with the exact location though.

  2. Jon Schwenk says:

    Hmm, if the green is true(ish) color, it might be an algal bloom. You can see a very large eddy to the left of the bottom-most meander bend, so it’s probably fluid as opposed to static vegetation. The shape of the lake points to a dam–doesn’t really look like a flood, since floods usually don’t occupy the side valleys so extensively. If the landscape were flat enough, though, it could be a flood. Also, if it were a dam, the river should not be so well-defined (or defined at all). So I would guess that it is indeed a flood, perhaps downstream of a lake (dammed lake?) that was undergoing an algal bloom.

    Here’s another question: which way is the river flowing?

  3. Manuel Carlos says:


  4. Steve Specht says:

    Upstream end of a reservoir, where the old river channel is flooded by the reservoir pool – from the vegetation and road/farm development, not in the US …

  5. Dorothy Cate says:

    I was told by someone that I got it right with Mekong Delta. Is that possible? I don’t doubt my answer, just that I could have been right about something. Is this true?

  6. Ajay says:

    Is it Cambodia…? Confluence of a couple of rivers with heavy sediment flow.

  7. Mike Walker says:

    I’m no ‘geo’ expert, but I reckon its unusual given the Srepok river (that’s normally ‘skinny’ ie the bright green trace), is now being overshadowed by the flooding due to the closing of the gates at the Lower Se San II dam….(Cambodia, Stung Treng Province).

  8. Anoop V Mohandas says:

    Satellite Image here is Landsat8 OLI data in Natural color Composite (RGB:321).Location:Cambodia.Looks Image taken during river is over flooded? or may be its near to any reservoir, siltation or sedimentation in the river is there because light color due to reflection of material.Meandering of river is also visible .

  9. Chris Mentrek says:


    It looks like a temperate zone, given the brown plants.

    I LOVE the meandering river. I think “downstream” is on the left, and “upstream” is towards the top of the image.

    It seems to be someplace where a flat, meandering river has built up banks on either side, and there are hills/higher land rising around it…

    (My first guess was that it was someplace like Lake St. Clair in North America, or Poyang Lake in China, where the distinction between “lake” and “slow-moving river” is blurred. I don’t know WHERE this image is!)

  10. EL says:

    Read more about it in image of the day? But the link takes me to another site, not the one describing this image.