# Those Ripples In Sand bars-Always The same Dimensions? **URL:** \ **Category:** In My Humble Opinion\ **Created:** [February 12, 2013, 6:38pm UTC](https://boards.straightdope.com/t/those-ripples-in-sand-bars-always-the-same-dimensions/650101 "2013-02-12T18:38:52Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![ralph124c](https://avatars.discourse-cdn.com/v4/letter/r/8797f3/32.png) [@ralph124c](https://boards.straightdope.com/u/ralph124c)\ **Post date:** [February 12, 2013, 6:38pm UTC](https://boards.straightdope.com/t/those-ripples-in-sand-bars-always-the-same-dimensions/650101/1 "2013-02-12T18:38:52Z")
If you go walking on a coastal sand bar, after the tide goes out, on the margins you will see a ripple pattern in the sand. These ripples are caused by wave action-are they always the same width and height? If so, why? ---
**Author:** ![CalMeacham](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/calmeacham/32/35_2.png) [@CalMeacham](https://boards.straightdope.com/u/CalMeacham)\ **Post date:** [February 12, 2013, 6:56pm UTC](https://boards.straightdope.com/t/those-ripples-in-sand-bars-always-the-same-dimensions/650101/2 "2013-02-12T18:56:15Z")
The ripple size depends on grain size and water flow. See here: > **[Ripple marks](https://en.wikipedia.org/wiki/Ripple_marks)** > > In geology, ripple marks are sedimentary structures (i.e., bedforms of the lower flow regime) and indicate agitation by water (current or waves) or wind. > > Straight ripples generate cross-laminae that all dip in the same direction, and lie in the same plane. These forms of ripples are constructed by unidirectional flow of the current. > **[Wave-formed ripple](https://en.wikipedia.org/wiki/Wave-formed_ripple)** > > In sedimentology, wave-formed ripples or wave-formed ripple marks are a feature of sediments (sandstones, limestones, siltstones) and dunes. These ripple marks are often characterised (and thus distinguished from current ripples) by symmetric cross sections and long relatively straight crests, which may commonly bifurcate. Commonly, these crests can be truncated by subsequent flows. Their wavelength (periodicity) depends on the sediment grain size, water depth and water-particle orbits in the w... There’s a sectiojn on Sand Ripples in Jearl Walker’s Flying Circus of Physics (section 2.110), but I don’t have my copy here: [http://flyingcircusofphysics.com/News/NewsDetail.aspx?NewsID=54](http://flyingcircusofphysics.com/News/NewsDetail.aspx?NewsID=54) (Look for “Sand Ripples” ---
**Author:** ![ralph124c](https://avatars.discourse-cdn.com/v4/letter/r/8797f3/32.png) [@ralph124c](https://boards.straightdope.com/u/ralph124c)\ **Post date:** [February 12, 2013, 11:07pm UTC](https://boards.straightdope.com/t/those-ripples-in-sand-bars-always-the-same-dimensions/650101/3 "2013-02-12T23:07:59Z")
Thanks! ---
**Author:** ![Dinsdale](https://avatars.discourse-cdn.com/v4/letter/d/97f17d/32.png) [@Dinsdale](https://boards.straightdope.com/u/Dinsdale)\ **Post date:** [February 14, 2013, 5:47pm UTC](https://boards.straightdope.com/t/those-ripples-in-sand-bars-always-the-same-dimensions/650101/4 "2013-02-14T17:47:06Z")
I walk along Lake Michigan several times a week - the ripples on the beach and under water vary tremendously from day to day. I suspect wind (direction and strength) to be the primary culprit. ---
**Author:** ![lieu](https://avatars.discourse-cdn.com/v4/letter/l/c2a13f/32.png) [@lieu](https://boards.straightdope.com/u/lieu)\ **Post date:** [February 14, 2013, 6:30pm UTC](https://boards.straightdope.com/t/those-ripples-in-sand-bars-always-the-same-dimensions/650101/5 "2013-02-14T18:30:49Z")
Generally speaking, ripple [size](http://www.google.com/imgres?q=ripple+size+wave+height+depth&hl=en&tbo=d&biw=1124&bih=755&tbm=isch&tbnid=M8BGft2bfKTVgM:&imgrefurl=http://www.springerimages.com/Images/Geosciences/1-10.1007_978-1-4020-3609-5_183-0&docid=NZXNZ53bVb4xlM&imgurl=http://img.springerimages.com/Images/SpringerBooks/PUB%253DSpringer_Netherlands-Dordrecht/BSE%253D5898/BOK%253D978-1-4020-3609-5/PRT%253D18/MediaObjects/WATER_978-1-4020-3609-5_18_Part_Fig12_HTML.jpg&w=300&h=181&ei=IikdUZzOCs7nqAG3sYDgAw&zoom=1&iact=hc&vpx=4&vpy=138&dur=2125&hovh=144&hovw=240&tx=142&ty=78&sig=116026351230573022592&page=1&tbnh=140&tbnw=233&start=0&ndsp=29&ved=1t:429,r:23,s:0,i:155) is a function of grain size, wave height and water depth. With an increase in these, say in a historic flood event, the [landforms](http://www.google.com/imgres?q=landforms+ripples+missoula+camas&um=1&hl=en&tbo=d&biw=1124&bih=755&tbm=isch&tbnid=WLDBJWwxLV_Z-M:&imgrefurl=http://www.iceagefloodsinstitute.org/floods.html&docid=tt2pIzPyVjB7PM&imgurl=http://www.iceagefloodsinstitute.org/photos/TF01.jpg&w=240&h=161&ei=wiwdUZSKCcOLqgG294GQDw&zoom=1&iact=hc&vpx=620&vpy=468&dur=2078&hovh=128&hovw=192&tx=100&ty=92&sig=116026351230573022592&page=1&tbnh=128&tbnw=192&start=0&ndsp=20&ved=1t:429,r:14,s:0,i:123) created can be enormous. ---
**Author:** ![ralph124c](https://avatars.discourse-cdn.com/v4/letter/r/8797f3/32.png) [@ralph124c](https://boards.straightdope.com/u/ralph124c)\ **Post date:** [February 17, 2013, 3:37pm UTC](https://boards.straightdope.com/t/those-ripples-in-sand-bars-always-the-same-dimensions/650101/6 "2013-02-17T15:37:38Z")
Thanks for the links-BTW-is the “angle of repose” for a pile of particles always the same? Piles of crushed stone always seem to be stable at the same angle.