Evaporites are rocks that are formed when minerals are left behind when water evaporates. This is how salt flats are formed. The earth was once covered by giant inland salt lakes. Over time these lakes dried up, but when the water evaporated the salt had nowhere to go, what is left behind is a wide expanse that is incredibly flat, and is comprised of a thick layer of salt (and other minerals).
Because of this high concentration of salt almost nothing will grow on these flats, making them seem almost like a giant white desert.
This experiment will show you how a salt flat is formed.
- One large glass or ceramic pie dish or baking dish.
- Four cups of hot water (be careful not to get burnt).
- Two cups of salt.
- Two tablespoons of baking soda.
- Two tablespoons of soil.
1. Stir one cup of salt as well as one tablespoon of baking soda and dirt into one cup of hot water. Stir the mix slowly until all the salt dissolves completely, let this sit for one minute, then slowly stir it again and let it sit for one minute.
2. Pour the mixture into your dish and let it sit somewhere that it will not be disturbed. Placing it in the sun or another heat source will speed up the process. Once the water evaporates completely you will have a layer of sedimentary rock on the bottom of your dish.
3. Repeat step one and two without using any baking soda or soil and using only half a cup of salt. Once this evaporates you should have a heavier layer of sediment that looks cleaner and is comprised of larger crystals.
Finally, complete steps one through three again.
You should now have your very own model of a salt flat. You will notice layers of clean and dirty “strata” or layers of sediment. It is in this way that many of the worlds salt flats have been formed.