Often times when most people think of lakes, they think of a classic 4-season blue lake. But the geographic diversity, mineral and chemical makeup and temperature range of lakes is vast! Learn here about the salt harvest from a lake: Lac Rose in Senegal.
Learning about geography is a great way to integrate a lesson about both science and culture! There are so many different types of lakes: thermal lakes, glacial lakes, volcanic lakes, tectonic lakes, underground lakes, landslide lakes, meteorite lakes… One of the most fascinating types of lakes or bodies of water are high salinity lakes.
There are a lot of high salinity bodies of water out there. Here’s a quick list of some of the most well-known.
1. The Great Salt Lake in Salt Lake City, Utah, USA
2. The Dead Sea bordering Israel and Jordan
3. Lake Hillier, Australia
4. Masazir Lake, Azerbaijan
5. Laguna Colorada, Bolivia
6. Champagne Pool, New Zealand
7. Salina de Torrevieja, Spain
8. Dusty Rose Lake, Canada
Lac Rose, Senegal
I hadn’t heard of pink lakes until my partner had several work trips to Senegal this past year and had the chance to visit the highest salinity lake in the world. Lac Rose (in French) but also known by some as Lake Retba (in Portuguese). Lac Rose is located in Senegal about 30 kilometers northeast of Dakar. The lakes hyper salinity is what gives the lake it’s famous pink hue that ranges from a slightly tinted rose to an ultra-vibrant pink during the dry season when salinity is at its highest.
The high salt content draws local salt harvesters to its banks. First, to protect their skin from the salt, they rub raw shea butter on their bodies before entering the water with woven baskets made from reeds with a rope attached. Once in the water, they place the basket in between their legs under water and using a shovel, they drag the salt into the basket.
More fun with salt? How about making a salt dough map?
Salt harvest in Senegal
There are three different kinds of salt. There’s a very powdery salt that is only in the lake during the Harmattan- the western winds that blow from the Sahara over West Africa every year. The powdery salt is used mainly for cooking. It’s seen as the finest or highest grade of salt. This type of salt is harvested using the basket and shovel method.
The second type of salt is a coarser salt that is always present at the bottom of the lake. This type of salt is also harvested using the basket and shovel method and is generally used for general cooking as it’s coarse enough to put into a salt grinder. Sometimes this type of salt is even used for roads. It’s also harvested using the basket and shovel method. The third type of salt is the coarsest kind that people prefer for their cosmetic or beauty treatments. To harvest this type of salt, salt harvesters wedge wooden stakes into the bottom of the lake and over time, coarse salt crystals begin to form on the wood. Locally, it’s put into body scrub and soaking treatments.
Lac Rose is considered a world heritage site and the community is generous with sharing the bounty of their local beauty. Everyone takes a little bit of what they need and nothing more.
The healthy, natural regulation of the use of the natural resources of this lake is one of the most impressive aspects of the community surrounding this lake. There are no laws needed to protect it. There is enough for everyone in the local community. This juxtaposition to an often exploitative capitalist and scarcity mentality that we see in many western countries is truly
quite refreshing and a good example of the power of mutual respect and trust in local community.
Science experiment: grow salt crystals
Ready for a science experiment? Time to grow salt crystals just like they do to create the third type of in Senegal at Lac Rose!
For this science experiment, you’ll need:
1. Popsicle sticks
2. Pipe cleaners
4. Sea Salt (table salt if sea salt isn’t available)
5. Hot water
Set up three mason jars 4/5 full of very hot water. While stirring add as much salt as you can until no more salt dissolves to create a saturated solution. By the end you’ll have a clear liquid with a little salt left at the bottom.
In one mason jar, put one popsicle stick in the water and leave it there. This stick method similar to what they do in Senegal at Lac Rose!
For the second mason jar, tie a string around a popsicle stick until there’s two 3 to 4 inch tails dangling off the end. Balance the stick on top of the jar so that the thread hangs down. F
or the third mason jar, use your pipe cleaner to create any shape you’d like such as a star, circle or diamond. Tie the thread to it, attach that thread to the popsicle stick and balance the popsicle stick so that the pipe cleaner is hanging down into the salt water. Cover each mason jar with a small piece of cardboard and wait 3-5 days.
Write down some hypotheses as to which method you think will yield the biggest salt crystals. The longer you wait, the bigger salt crystals you should see form!
Which of your hypotheses correct?
Are you looking for more STEM fun? Take a look at our math and science night.
About the author: Alexandria Scott is a writer, educator and community advocate who helps readers better connect students and educators as well as children and parents to access and internalize multicultural and anti-bias education. She is the editor of Ditto Kids.