Many of us have seen old lava flows and volcanoes - but did you know that you can make a yolk volcano? I didn't until I discovered it by accident (... and despite my best efforts I have not been able to replicate it).
How to find it
You will know one of your hard boiled eggs harbors a yolk volcano if you find the following yolk strings in the water:
The source of the flow
Follow the strings until you find the source, you guessed it, a hole in the side of the egg where the shell broke and the yolk slowly oozed out, boiling along the way.
Peeling away the outer layers shows the structure of the volcano where the yolk (magma) broke to the surface of the white (crust).
Splitting open the yolk you can see the stress fractures in the direction of maximal ooz.
But what pushed it out?