I know you have seen these before. I remember playing with bottles to make the swirling tornado just by doing a quick swirling motion with the bottle. I loved that and my kids always love anything that involves a good mess.
1. Plastic Bottle
4. Food Coloring
Fill the bottle 3/4 full with vegetable oil.
Fill the rest of the bottle with water (almost to the top but not overflowing).
Add about 10 drops of food coloring of your choice. Be sure to make the water fairly dark in color.
*~*~Notice that the food coloring only colors the water and not the oil. COOL
Another Super Neat option for a lava bottle is to drop in a alkaseltzer tab and place a flashlight under it and watch it bubble.
Alkaseltzer Bubbling Lava Bottle:
** We used a recycled water bottle which takes less liquid than the vase used in the above video; making the liquid measurements different.
CON: After going through a few runs of putting a tab in to watch it bubble the oil starts to turn cloudy. I only had the orange alkaseltzer tablets here, so I don't know if that is why. The flashlight under the bottle was a really great idea.