Try some red lava in a cup and see what's going on?
Steps to be taken
Fill the glass about 3/4 full of water.
Add about 5 drops of food coloring - I like red for the lava look.
Slowly pour the vegetable oil into the glass. See how the oil floats on top - cool huh? It gets better.
Now the fun part: Sprinkle the salt on top of the oil.
Watch blobs of lava move up and down in your glass!
If you liked that, add another teaspoon of salt to keep the effect going.
How it happen?
Of course, it's not real lava but it does look a bit like a lava lamp your parents may have had. First of all, the oil floats on top of the water because it is lighter than the water. Since the salt is heavier than oil, it sinks down into the water and takes some oil with it, but then the salt dissolves and back up goes the oil!