Chocolate Pillow Lava

When lava erupts under the sea it forms pillow lava.


Hershey's "Shell" chocolate syrup, it comes in a squeeze bottle.

A clear plastic container at least as wide as a drinking glass. (e.g. a plastic salad tray from a supermarket or a clear plastic plant tray.)

Ice cold water.


Fill the plastic container with water.

To Do and Notice

Put the mouth of the chocolate syrup under water near the bottom of the container and start to squeeze out chocolate.

Notice that the chocolate flows out easily at first, but when it hits the cold water it solidifies into a crust.

As you continue squeezing the crust cracks and the chocolate flows out of the crack.

The process continues making a stack of crust encased lava-like pillows.

What's Going On?

The cold water causes the outside of the liquid chocolate to chill creating a crust.

Under the pressure buildup from the continuing flow from the squeeze bottle the crust cracks and liquid chocolate flows out of the crack.

This newly exposed chocolate continues the process by cooling to form a crust.

So What?

The same thing has been photographed happening in Hawaiian undersea lava flows.

The molten lava produces pillows when it hits the cold sea water. The outside of the molten lava chills to form a crust. Then this crust cracks under pressure from the lava inside and new lava bulges out of the crsck to create a new pillow.

These pillow lavas are often seen on land when undersea volcanic rocks are uplifted.


Lee Tepley made a movie showing the formation of pillow lava when lava flowed into the sea in Hawaii during a 1971 eruption of the East Rift Zone. The name of the movie is "Fire Under the Sea." Images of undersea lavaflows are also available on the web, do an image search for the term "pillow lava."

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Scientific Explorations with Paul Doherty

© 2002

6 August 2002