Sunday, October 11, 2009

Sands of Time

The Florida plateau, that part of the Earth that holds Florida up out of the ocean ... at least for the moment ... was formed just 530 million years ago. As well as being much larger in the distant past, it wasn't really recognizable as FLORIDA until between four and six thousand years ago. Then you would have found it familiar... bays, estuaries, Everglades, and of course, beaches.

Florida Beaches are a treasure in sand. It is a matter of perspective we don't truly understand while we remain Earthbound. Even from space it is difficult to grasp.

It is a rare day when the entire coastline of the southeastern United States is cloud free at the same moment. January 9, 2009 was nearly such a day, and, from the perspective of the MODIS instrument on the Aqua satellite, the ocean also happened to be sunglint free at the same time.

We often take our beaches for granted, though: Before you curl your toes into the warm beach sand or run splashing into the water, take a moment to partake in the wonderful world of coastal formation! Coastal formation occurs on several scales, ranging from the motions of the planets all the way down to the interactions of molecules of water.

On the largest scale, coastlines are formed from two processes: coastal emergence and coastal submergence. Coastal emergence happens when land emerges out of the water. This can occur, for example, when a mountain range at a plate boundary is uplifted. Imagine the coastline of Chile, closely paralleled with the Andes Mountains. Millions of years ago the Andes were pushed up from the crust, forming a new coastline.

Far more coastlines, however, have been formed by submergence. Coastal submergence occurs when the water level of the ocean rises significantly, flooding formerly inland regions. The entire east coast of the U.S., for example, is a coast of submergence. The majority of today's coastlines are of this type because of the rise in sea level following the last Ice Age.

There are many ways that coastlines are continually changing...Coastal Processes

Beach formation on a more familiar scale deals with actual aggregate movement- SAND. Put simply, the Sand Man's day job is to shovel beach sand, a lot of beach sand. The movement of beach sand happens in two ways. The movement of sand perpendicular to the beach and the movement of sand along the beach. Both are caused by a combination of wave motion water currents, and wind. Wave motion animation.

Sand movement toward and away from a beach is dependent largely on the TYPE OF WAVE. Waves known as spilling breakers, or constructive waves that surge water up on the beach, depositing sand and dissipating the wave's energy. A Plunging breaker, or destructive wave, tends to collapse in on itself, sucking sand away from the beach in a backwash and contributing energy to the following wave.

Currents also have a significant effect on the movement of sand in and out from the beach. If waves are responsible for the movement of sand on and off the beach, then currents are responsible for the movement of sand to and from the waves. Beaches are always on the move! Check out the SWASH?

Imagine a grain of sand being taken away from the beach. As this grain is swirled about in a tempestuous fury of foam and churning water, it is eventually picked up by a current known as a rip current or rip tide. These "rip tides" funnel outward between underwater sand bars and then die out in deeper water. The grain of sand then drifts towards the sandbar, settling down until picked up once again by an incoming wave. That wave will eventually deposit the sand on the beach, repeating the cycle. Because rip tides only occur between breaks in under-water sandbars, they don't have enough force to cause a net movement of sand away from the beach.
(Thank you

(If you're ever stuck in a riptide, swim parallel to the beach and you'll soon escape its grasp!)

Another type of current, known as long-shore drift is responsible for the movement of sand parallel to the beach. Long-shore drift occurs because waves often strike beaches at an angle. When they do this, the waves deposit sand along one direction and pull it away on another. This tends to form a zig-zag movement of sand along the edge of the beach, pushing sand in the direction that the waves are striking. This movement is responsible for the formation of several coastal structures including spits, hooks, tombolos, and coastal bars.

This drift has important consequences for the man-made development of coastal regions. Beachfront worth billions of dollars in property value can disappear as sand slowly moves down the coast. Many coastal towns build erosion control structures along their beaches... not always with the greatest of success.

Groins, jetties, seawalls, and breakwaters are basically walls made of concrete, wood, or piles of rocks in attempts to manage the flow of sand and reduce coastal erosion. The continued over-development of coastal regions is just like building your house on a sea-side glacier. Sure, it may look stable now... but eventually it really is going slip right out from under you and fall into the sea.

It's just a matter of time.


Juliane likes this site... for longshore current

Lexi, you might be interested in the Rubber Ducky study.

The comment box is open?

What do you think?

Are we ignoring science when we build right on the beach? ..Is that a good thing?

What more would you like to know?


  1. If we do build some kind of erosion control on one place does the water move differntly and cause some kind of differt erosin else where? Are we fxing it in one place and adding headach for others? Why do we need to build more, there is enough places that are empty. Lets stop building and messing up our earth so much.

    ryan (violet)

  2. I have been pulled in by a rift tide before while I was boogie boarding!!! now I understand why. It felt like I got sucked in.

    ___________lindsey green____________

  3. Ryan, excellent thought about passing the headache on to someone else... down the coast... that's exactly what happens.

    Lindsey, you are lucky. Some rip currents are very powerful. Remember the rules of survival.

  4. So Mr.V are you saying like if you don't be careful you might get lost at sea because the Rip Currents pull you out?
    The sooner the people learn about the Earth and the Oceans they should stop stop messing with our earth.
    That would be so cool if you built a house on a glacier!But it would be sad to watch it wash away because of the Currents...

    Michelle M. Yellow

  5. spencer (green class)October 12, 2009 at 8:26 PM

    mrv do you need speakers for the clip because i dont have any sound and i think thats a problem

  6. Spencer, yes your computer would need to have a speaker. Sorry.

  7. Michelle, the question is, does it really make sense to build on a sandbar? They move like glaciers do.

  8. 540 million years ago! Thats a long time ago!

  9. Dear Mr. V,

    I found a web site that explains a vocab word. The word is long shore current. Heres the web address.
    Hope it comes to use.thanks,

    Juliane W P.3 Y

  10. Juliane , thanks for the website, I will add it to the blog and others can check it out.

  11. Wow the blog has all of the *KEY Words that we need to put in the glossary...It was really useful

    Michell M. P.3 Yellow

  12. Dear Mr.V,
    thanks for showing me that video about how to get out of a rip

    Chris S.

  13. Michell, I am glad you found this blog to be useful and Chris, I hope you never get "caught" but now you have seen how to "escape" a rip current in case you do.

  14. I think that it is helpful to tell people how to get out of a riptide if they get caught in one because we live in Florida where they occur alot.

    Jordan Orange

  15. this class rocks

    jaide yellow

  16. i like how the picture of florida shows the actual picture of florida and how deep it is off the coast

    branden {yellow}

  17. Thanks Mr.v for sharing this article with me.I found some interesting facts such as the florida plateau was formed 530 million years ago.I also found out that the coastlines are formed form 2 processes coastal emergence and coastal submergence.


  18. Mr. V
    This blog is so helpful to me because i go to the beach alot and swim in the waters. Now I know how to get out of a rip tide! I think it is so NOT helpful to build right on our beach. We seriously need to stop!!!

    Kailey (green)

  19. Mr.V,

    I think the Swash diagram was really interesting and it makes a lot more sense when you're looking at it.

    Caitlin Green

  20. I think it is so cool that you told pepole how to get out of a riptide that can really come in handdy.

    Malone green

  21. yes we are ignoring science we should really pay attention. this is a very bad thing we are doing

    lexi green

  22. I think it is very important to know how to get out of a rip tide since we live in florida.

    lexi green

  23. I would like to know more about swash.

    Lexi green

  24. Mr V,
    i liked the video of how to get out of a ripcurrent it will probably come in handy for me because i surf in Costa Rica all the time and the ripcurrents are very strong there.

    sydney(paula) green.

  25. thats cool how the florida pleatu was formed 530 million years ago and you could only start to reconize it four to six thousand years ago kenny yellow

  26. WOW =-you guys are leaving such great comments.

    Sydney "Green" YOu surf in Costa Rica? How cool is that!

    Lexi, you can explore "swash" yourself with your next trip to the beach... Toss a rubber ducky in and track how it moves. There is a famous scientific study on the oceans and rubber duckies....

    Check it out.

    Bye gang

  27. I watched the video of erosion on youtube. In my science class we just finished talking about erosion, and how it can erode parts and the sides of cliffs over a lond period of time. It was very interesting.

    Garrett (Green)

  28. After my mom and I were done watching the riptide survival video, she told me about a time when she was surfing on the east coast of Florida and her surfing guide lender her a pair of his sunglasses and she dropped them when a wave hit her and she went under to grab them but when she came back up... She was around 40 feet behind of where she originally was. (Out past the breakers.) She would have drowned if a boy on a surfboard didn’t come get her. She stressed to me about how important that video really was. Always swim pare all with the beach, and then swim at an angle towards the beach.

    Garrett (Green)

  29. I'm really injoying this class thanks to this blog and this well put together website!! Some of my other teachers dont even have a blog, a couple have a wesite that hasnt been updated like since the sencond Third week of school unlike this one its beeing updated every single day and I think that is really cool!!

    Garrett {Green}

  30. I think that the more of the more the barriers the more sand if because the rock will decay.I think that we are destroying the habitats of marine life.I would like to know more about the construction on the beaches

  31. I think that the barriers will bring more sand once they decay.Yes we are and that is not a good thing because it is killing animals.I would like to learn all the effects of off shore drilling and the buildings on the beach

    Christian (Violet 6)

  32. I like how they put hunor in the artical. "The sand man's day job is to shovel beach snd, alot of beach sand." :)

    corwin (green)

  33. how many times would a rare day come when the entire coastline of the southeastern united states is cloud free at the same moment come in a year?


  34. Mr. V i really liked the videos that really helped me understand more about erosion and weathering.

    Crystal Bell

  35. Mr. V i really love your class it is very organized and planned