Wednesday, September 16, 2015

Search Challenge (9/16/15): How to describe the hills?

I climbed the hill... 

... and just a bit more down the path, I climbed another one just like it.  A bit more down the path, ANOTHER one just like it.  Interesting--how long would this repeated series of seemingly identical hills go on? 

As I flew across center part of the US yesterday, I had a window seat and able to peer out the window for much of the flight. What I saw amazed me, and it reminded me of that repeating hilly path.  I kept seeing waves upon waves of stone and sand, patterns written in the geography.  

One of the problems we have as writers is knowing how to describe places in ways that are evocative AND descriptive enough that you get a great sense for what it's like to actually be there.  

I can tell you the path I was on was a jungle path, or a desert path.. but it's hard to be precise about the path per se.  

Tony Hillerman might write "...the eroded flanks of the hills covered with an infinity of dark green creosote bush and the grey-white desert grasses...", or Hemingway could say "... Hills terraced and yellow fruit shining through the green leaves and darker green of olive trees on the hills, and streams on the hills, and streams with wide dry pebbly beds cutting down to the sea and old stone houses, and everything all color."  These are beautiful, but vague.  

Face it, I've got an engineering heart (wrapped in the pulsing body of a poet), so I'm looking for something a bit more.. precise.  How far apart are those hills?  How high and low do they go?  

Here's one of the sights I spied from my window seat (this is part of Point Reyes, CA, near Bolinas Lagoon).  Note the repeated foldings of the hills. That's a lovely pattern--now, how can I describe it?

Here's a map of that same area: 

As you can see, the streams are all parallel, telling us that the hills and valleys are all parallel as well--repeated ridges marching next to the San Andreas fault.  

Now suppose you drew a line like this across the tops of the hills, streams, and valleys:  

If you drew the cross section of this piece of the land, you'd see something like a sine wave, 

As you know, a wave like this can be neatly described by its frequency (how many up/down cycles happen per unit time, e.g., 440 cycles/second), and its amplitude (how for up and down the wave goes--in this case, the amplitude for the sine wave above is 1--it goes 1 unit up from the centerline).  

Now, if I want to describe these hills in Point Reyes, I thought about describing them in terms of their frequency.  Some hills have a high frequency, while others have low frequency, but a high amplitude.

With just a couple of searches, I was able to figure out the answer to today's Challenge.  Can you?  This Challenge comes in a couple of parts.  Even if you can't figure out how to do parts 1 and 2, EVERYONE can do something on part 3.  

1.  Does the term "frequency" make sense when applied to repeating hills?  Frequency is usually defined as cycles / unit-time.  Can you figure out how to apply the concept of "frequency" to hills?  
2.  What's the frequency (however you define it for hills) of this stretch of hills above?  You'll have to find it, measure it, and then figure out the "frequency," if you can!  
3.  Can you find a stretch of the Earth that has a nicely repeating pattern to it similar to the one above?  If so, where is it?  (Give us the lat/long in your answer.)  

As always, be sure to tell us HOW you found the answer.  

I can't wait to see what glorious hillsides you'll find!  (Be sure to tell us how you found them.  Did you just know about them?  Or did you actually do some kind of search?)  

Search on!  

P.S.  I will be traveling again next week when the answer is supposed to come out.  I might not be able to get to an internet connection to post my result.  But stay tuned... you never know... I'll definitely post how I solved it. 


  1. #3 - First area that came to my mind was what is known as the Badlands near Drumheller. I have enjoyed hiking in this area. This particular hiking area is known as Horsethief Canyon. Interesting patterns. 51.5380342,-112.8688627

    1. Hereś a site with some better images that gives a better perspective of the canyon.

      What I think is interesting in relation to this challenge is that if you walk around the rim of this canyon there are fields & prairie. The land is absolutely flat and if you were to walk a 1/2 km back from the rim you would not even realize this canyon existed. Now in regards to the challenge the fact that the canyon is below the surrounding terrain I wonder if that would have any impact. I will see what I can come up with.

  2. I am working to solve the Challenge. Here is what I am trying:

    1. Find the name of your Hills. After defining hills.
    2. Search for the key word. Topographic Prominence gives I think some clues.
    3. Find the correct tool. I thought a Topographic map could help. Now, I thinking something different.

    For Q3, I tried [List of hills] and [list of hills California] I can not find yours yet. Looking for examples, found this mentioned [Chocolate Hills] and searched for it.


    [Chocolate Hills Latitude Longitude] 9.9167° N, 124.1667° E

  3. Trying to define and understand the Challenge. Now, I got confused with terms:

    Colina (Hills in Spanish) Dr. Russell's photo looks like Cordillera

    Hills, English Wikipedia.

    1. After looking Chocolate Hills, visited Terrain View in Google Maps and searched:

      how measure topographic hills


      Sierra Madre Oriental and Occidental have beautiful patterns. They are Mountain Ranges.

      Sierra Madre Oriental, aerial view Lat/Long : 25.3667° N, 100.5500° W

    2. I was looking Fundeu. (I ithink RRR will like it) and found 2 very interesting articles in Spanish, that are related to SearchReSearch.

      De dónde vienen los nombres de los sistemas montañosos de España? About Mountains and more and how they got their name.

      Todos los mapas que conoces están mal About Maps.

    3. Ramón, Es verdad, los dos artículos son muy interesantes. Agradezco que las has compartido con nosotros. Me gustaría pasar más tiempo en los retos pero estoy muy ocupado con español estos días. Seré asistir una escuela en Guanajuato en el enero por varias semanas. Todavía voy a tratar de contribuir algo cada semana para estos retos. Y leo todos sus comentarios y como siempre aprendo algo en las soluciones. Espero que puedo añadir algo más tarde.

      (The two articles are very interesting. I appreciate that you shared them with us. I would like to spend more time on the challenges but I'm very busy with Spanish these days. I will attend a school in Guanajuato in January for several weeks. Still I will try to contribute something for these challenges. I read all your comments and as always I learn something in the solutions. I hope to add something later.

    4. стараюсь SRS инструменты - Plateros испанской школы, примерно в 30 милях за пределами Леон?

      starayus' SRS instrumenty - Plateros ispanskoy shkoly , primerno v 30 milyakh za predelami Leon?

      (trying my sRs tools - Plateros Spanish School, about 30 miles outside Leon?)

  4. Hello Dan and fellow searchers,

    I first searched for things like [succession hills] [succession hinges] [succession peaks] then added 'geology' [geology succession hills] etc. but nothing to find.

    So I tried [geology frequency] to see if the two terms were connected. Hmm not much. But I know that most sciences have dictionaries of the terms of their field of research. [geology dictionary] in books gave 'A Dictionary of Geology and Earth Sciences', exactly what I was looking for.

    Then in the dictionary the 'frequency' entry says 'the number of wavelengths which pass a given point…' That's it, I remember frequency is expressed in Herz which is a number of peaks per second and wavelengths are in meters which describe the distance between a peak and the next. That seems more appropriate for measuring geological patterns. And indeed the 'wavelength' entry says exactly: "in a fold system the distance between one hinge or trough and the next.'

    So here we are: 'wavelength' seems to be the appropriate term to describe the succession pattern of hills.

    Given my background, it's pretty obvious to calculate the wavelength of the hills near Bolinas Lagoon but I won't spoil it (I used Google Earth…)

    I'm still looking for such pattern in France where I live.

    Happy search.

    1. After reading Passager post, I have been trying new ways to find answer.

      I think he will answer q2 with wavelength and the distance of the hill. I was thinking counting the hills in Topographical Maps instead of wavelength, as one possible way. However, my path, looks like I can make many mistakes because lines can be mixed. I hope later, Passager show to us his method.

      Dr. Russell, you say: "With just a couple of searches, I was able to figure out the answer to today's Challenge." With those searches you found how to do the math or you found the answer in numbers?

      Remmij, I still need to visit your links. And, Maya links are very interesting.

  5. The red line: I replicated that and got elevations showing as wiggly line in GE. But I have no idea how to interpret this into frequency that the ravines appear because the whole ridge is random mess of all kinds of that erodes at different rates.

    This was confirmed by me by pal who is a professional geologist. He doesn't understand frequency without a time scale.

    Good and long explanation of the whole area

    THe atretch of hills covered by your red line is known as Bolinas Ridge

    Everything on the east side of the fault belongs to the Franciscan Complex, a big, sloppy geologic unit that includes bodies of sandstone, chert, shale, volcanic rocks and serpentinite. Parts of it are so mixed up that geologists have thrown up their hands and called it melange

    It seemed to me that Cordillera is the descriptive term here. And so it is. I think.

    [cordillera folding point reyes]

    [map geology point reyes]

    #3 Canada's Coast Range is Cordillera--the entire west coast.

  6. So, to calculate the wavelength, in Google Earth I found Bolinas Lagoon, draw a line just like Dan did, clicking a the starting and end points, and in the tool window in the measure tab i read the value. Then I counted the number of ridges along the line and divided the length of the line (in km) by the number of ridges to get the wavelength. In my case the length was 13.8 km for 26 ridges, which gives a 530 meter wavelength. That means that the pattern hinge-trough reappears about every 530 m. I guess the measure must not be that precise due to the irregularity of the pattern. A 6.2 km line at the beginning of the red line, by the sea, gives 10 ridges and a wavelength of 623 m. We could say that the pattern has a wavelength of the order of half a kilometer.

    Jon, a frequency always indeed involves time. By definition it measures the "number of something" by unit of time, the "rate of occurence" of some event. I thought at once that the term we were looking for could be the 'spatial frequency' which is defined as "a characteristic of any structure that is periodic across position in space (WP), often used in image analysis. It's related to the wavelength by the formula : SP=1/WL. But this term doesn't appear to be used in geology.

  7. Here is my geologist's analysis

    OK, what I noticed that is missing for me is: there is no scale, so I'm assuming not a large area (think I can see individual dwellings), the pattern seems different on the right (but in shadow) but I assume the ridge is higher to right, it may be close to a sine wave but I see more variation than the graph suggests.

    What I think I see is a fan pattern at the top with the tributaries coalescing into a single v-shape (especially at the left)- suggests unconsolidated material (look at a sand pile in a gravel pit), as you go right the 'stream' (seasonal or intermittent?) valleys get deeper (I assume- no 3D image) and the erosion is more apparent on the valley sides (suggests most all of the hills are unconsolidated but also fairly compact, ie not loose sand, but maybe sand and gravel or compacted sand or even friable sandstone (seen stuff like this in Alberta in soft sandstone) but not hard bedrock as this would produce cliffs and step valleys). Don't think it is till (glacial 'boulder-clay') as this could be fairly resistant (steeper sides) and not layered clay-till-sand as I don't see any sliding (not given any elevations however), The fan erosion patterns are nicely distinct so probably not lots rain and maybe periodic (seasonal). The front (parallel to red line) is sudden- a fault line with vertical displacement or (not here) along edge of major spillway (see this on Prairies).
    So, maybe alluvial plain or outwash from distant former glacier, cut by ephemeral or seasonal streams along up-raised side of fault line higher relief on the right side of photo.

  8. I did a "reverse search" on my answer (a trick I often use to check a notion, here wavelength) in Image search and I'm not sure that wavelength applies to the succession of ridges and troughs near Bolinas lagoon. The notion of wavelength seems to be specific to the study of folds as illustrated here, and I couldn't find an example of this term used in the case of an erosion pattern due to streams. And even if the notion of wavelength could be used to describe anything repeating in space, it doesn't seem to be commonly used (dunes apart). Let's wait for Dan.