A friend of mine gave me this recipe about 20 years ago. Its a fun and creative way to entertain kids at birthday parties and other fun events! It's also great for family projects, because everyone will enjoy the entire process of making it, quaking it and eating it!
Buy a can of pressurized whipped cream and take it to a hardware store. Buy 2-3 feet of plastic hose that will fit snugly onto the plastic nozzle of the whipped cream can. If you can't find a hose that fits tightly, come as close as you can. You can build up the width of the nozzle of the can by wrapping tape around the nozzle until the hose fits.
Now take the cardboard base of the cake and cut it into two equal pieces lengthwise. Take can of whipped cream and holding upside down, empty about half of the contents into a bowl for additional frosting.
Now take balloon and fasten securely on one end of the hose, taping or tying so that no air can escape. Lay the balloon and hose on table where you want to display the cake. The other end of hose should be over the edge of the table, attached to the top of the whipped cream can nozzle, sitting on a chair. Place cardboard base on the table over the balloon so that each half of the cardboard rests on top of balloon, with hose under a full piece of cardboard.
Next, place whole sheet cake on cut cardboard base so cut line is in center of cake. Now make a jagged cut across center of cake, cutting it into two pieces along the cut line of the cardboard base. Frost the cake and decorate it with small plastic Monopoly buildings, trees, etc. Make it look like a city-scape. You are now ready for the special effect. Sit in the chair and hold the whipped cream can in one hand in an upright position. Hold the hose firmly on the nozzle with the other hand. Announce that you think you feel an earthquake and depress the nozzle for 1 to 2 seconds, two to three times. This will partially inflate the balloon enough to make the cake slightly rise up. Then depress nozzle again for 3 to 5 seconds and the balloon will push up the center of the cake, revealing the jagged edges and pulling and stretching the frosting across the gap. Pull the hose away from the nozzle slightly and the cake slowly sinks back into position. Repeat as long as your pressurized can lasts. Most folks want to see it several times, so have fun!