Grade Level: 4th to 8th; Type: Geology
Create your own miniature salt flats at home.
Evaporites are rocks that are formed by the minerals left behind when the water they were dissolved in evaporates. This is the process that created the great salt flats in Utah, for example--those are mostly made up of evaporates.
- How do salt flats form?
Terms to Know
- Glass or ceramic pie dish or casserole (if you must use metal, make sure it’s a disposable pan or dish; the salt will wreck metal)
- 4 cupshot water
- 2 cups salt
- 2 tablespoons baking soda
- 2 tablespoonssoil
- Slowly stir a half cup of salt, one tablespoon of baking soda, and one tablespoon of dirt into one cup of hot water until the salt dissolves completely. Let it sit for a minute, then stir it again and let it sit for another minute.
- Pour the mixture into your pie dish and set it somewhere out in the open where it won’t be disturbed. Wait for the water to evaporate completely. This may take only a day or so, or it may take several days, depending on conditions. What you’ve got in the bottom of your pan is like a layer of sedimentary rock that is left after the water that brought the minerals somewhere has evaporated.
- Repeat steps one and two, but this time just use half a cup of salt, no baking soda or soil. Now you should get a layer that looks cleaner and has larger crystals.
- Repeat steps one through three. Now you should have your own model salt flats that alternate “dirty” and “clean” strata, or layers, showing clearly how the layers are formed. Salt flats are formed in much the same way, with water that has a lot of salt and other minerals in it evaporating and leaving the minerals behind as sediments that form layers over time as the process repeats itself.
Dig It!: Over 40 Experiments in Geology, by Lockwood DeWitt and B. K. Hixson, pp. 175-180 (Loose in the Lab Science Series, 2003).