Coastal Erosion

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SWBAT describe the process of erosion on the beach.

Big Idea

Discovering the differences between erosion, weathering and deposition is exciting in this lesson. It graphically and visually demonstrates how beaches can erode and change.

Setting the Stage

5 minutes

During this lesson I directly demonstrate the investigation.  I do this because I want to avoid any larger messes that could potentially take place.  In earlier lessons, the children worked very well with tubs of water, however, in those lessons, they really did not move the water around.  In order for this lesson to really get the full effect of what it is to do, the water needs to move in a wavelike motion. Knowing little boys and the excitement that could ensue; I make the decision to remove that temptation and directly demonstrate. 

This lesson is designed to demonstrate 2ESS-1.  Erosion is a very slow process and one that cannot easily be observed over time to really see the incredible effect it can have on the Earth.  The standard clearly states that students will use more than one source to provide evidence that events can occur quickly or slowly.  While I am demonstrating the lesson on the big screen, the students are able to witness on a small scale the beach erosion.  At the end of the lesson, a video clip shows a time lapsed video of beach erosion.  This provides two sources to witness this phenomenon.  

I have put sand and water in a small tub with a lid.  I mound the sand up to one side to resemble a beach dune and fill it, with about two inches of water. I also add three small sea shells that I place at the top of the beach dune. This will allow the children a reference point or a model (SP2) to watch when the water begins to move the sand.   

I set the water tub on my document camera. This allows me to make it possible for all the children to observe the lesson on the screen. I can easily talk through the lesson and describe each step of the process while the children are watching the erosion events on the screen. 

I am fortunate, in that my screen is very large. When images are enlarged, no matter what vantage point the children are sitting at, they can see the entire process.



5 minutes

The children are settled and I ask them to look at the screen. The Beach Erosion power point is ready and on the screen.  I anticipate there will be excitement.  Earlier when I taught the Alpine Unit, a lesson on Erosion was a huge hit (SP6).  And I want the students to understand that erosion does not only happen in the mountain setting.  I want to make this clear to avoid any misconceptions for the students learning. 

I explain that we will be talking about erosion again in this lesson, but it will have a different twist. I quickly move to slide two and ask the children to get comfortable and to close their eyes. I explain that I am going to play a video clip that has sounds I want them to listen to.  I want them to visualize being at the beach and imaging the waves lapping at their feet. This is the video clip that I play. In my slide show, it is embedded within the power point.  

I play the clip two or three times, while the children sit quietly with their eyes closed.  

I ask the children to open their eyes.  On the screen slide three asks, "What do you believe happens to the sand that is caught in the waves on the beach?"  It then suggests that the children turn to their team and have this conversation (SP1).  

The children share their ideas with each other first and then share out with the class afterwards. I move to slide four and ask this follow up question..."Can you think of anything else in nature that gives you some ideas about beach erosion?" I am hoping they will make the connection to prior lessons. 

I switch my projector to the document camera setting and explain to the children that this investigation has the potential to become very messy. To avoid this, I am going to do the investigation and they are going to watch on the screen. 

I direct the children to observe the placement of the sand and to notice the small seashells that are placed at the top of the sand mound.  


10 minutes

I take a small plastic sand shovel and slowly begin to move the water in the tub.  I am careful to make sure the movement of the water is gentle and not making much impact on the sand.  In the beginning, I do not want there to be any sand on the bottom of the tub where the water is.  I want it to remain mounded up on the side showing the beach dune.  

While I am slowly creating gentle waves, I am talking and modeling questions I want the children to be thinking about as they are observing.

  • What do you see?
  • What do you notice is happening, if anything?
  • Is anything happening to the sand?
  • What kind of waves are you observing?
  • How long do you think it will take before anything happens?
  • Do you think anything will happen?

All the while, the children are watching and listening. The classroom is silent.  (I think they could be holding their breathe). 

After about five minutes of this, the motion and action of the 'waves' begins to move the ocean. Sand has slowly redeposited on the bottom of the tub.  Just a small amount.  

I continue to make waves and the sand is beginning to move more.  Because it is getting wetter, it is loosening up underneath the bottom layer of the sand. This is helping to loosen it up and move it more easily.  The sand is beginning to move more freely now and the bottom of the tub should begin to have more sand.  

This process will take about ten minutes to continue to move the sand from one side of the tub and eventually spread it out evenly in the bottom of the tub.  

The children are continuing to observe this action throughout the entire process.  What was once quiet calm, is mounting and the children will begin to anticipate what will happen when the sand finally erodes away. 



10 minutes

I switch my document camera back to my Smart Board screen and show the children slide five and we review what erosion is.  Slide six is a review of weathering.  Slide seven is new....deposition.  The demonstration of the waves and the sand have visually demonstrated this process for the students. 

I ask the children to come and join me on the carpet.  I ask them to bring  their pencils and clipboards.  I pass out sketching paper (really it is just small pieces of blank paper) to each child and we settle in. I have an anchor chart ready to begin working on.  

I explain that we are going to create a chart to help us bring all this learning into one place.  While I am sketching out the ideas on the big chart, I ask them to recreate the same anchor chart on their smaller sketching paper.  I also tell them that we will glue these finished sketches into their journals when we are finished.  

I begin with the clouds at the top of the chart, using blue ink.  I am careful to make sure that my colors also represent the different elements of what we are discussing as I am filling in information. I next move to the mountain and then finish off with water at the bottom.  I allow the children a few minutes to complete their sketches and I remind them that is not art and we do not need to be perfect.  Just accurate.  I also explain that they will be able to go back and color their sketches with colored pencils after we have finished. 

Once the beginning stages are on the chart, I ask the children to think back to our lesson on erosion during the Alpine unit.  What do they remember about the weathering and erosion from those lessons? I expect to hear we had rain and wind. 

I draw raindrops and snowflakes on the chart. I next add the water flowing downhill leading into the water at the bottom of the chart.  I go back and draw in large 'boulders' and then ask the children to tell me what happens to those boulders during all this weather?  I expect to hear them explain the weathering process of breaking down the rocks.  I follow up with one more question....what happens to the smaller rocks after this? I want to hear them explain to me that the wind and other elements will move the rocks to other places. 

I complete my anchor chart with the information the children have shared with me and allow them time to finish their charts as well.  When all the sketching is completed, I add three more pieces of information.  The language of the chart.  This is the most important part.  


10 minutes

Next, I show this short video clip to the students. This may happen the following day depending on time.

I tell them to focus on the rocks that are on the beach.  The video clip is a time lapsed view of what happens to a beach when the waves continue to move and redeposit the sand and rocks.

I ask the children to turn to their shoulder buddy and have a conversation about what we discussed and learned the day before about beach erosion.  I want to know if the information has remained with them.  

I am hoping to hear them explaining to each other the process it takes for the rocks to be broken down through weathering and erosion and eventually deposition.  I leave the anchor chart up for those students who might need reminders. 


10 minutes

When all the charts have been completed, I instruct the children to return to their tables and glue their sketches into their journals.  I also ask them to write in their journals what they have learned about the process of the deposition. I circulate through out the classroom as the children are working and writing.