Cyclic hot water fountain

Natural geysers form when underground chambers fill with water and are heated geothermally. When the water is heated to its boiling point, the geyser erupts, spewing its contents, and the cycle starts again.

 Ring stand

 Metal ring

 Hot plate or other heat source

 Plastic food container

 Glass tubing (.5 to 1 meter in length)

 Boiling or Erlenmeyer Flask

 One-hole rubber stopper

 Plumber's putty

 Timing device (stopwatch or clock)

1) Drill a hole in the center base of your plastic container (a sharp, pointed knife twirled in a circle makes a great drill). The hole should be just large enough for the glass tubing to be snugly inserted.

2) Position an unplugged hot plate next to the base of a ring stand and set a boiling flask filled with water on top of the heating unit.

3) Carefully insert one end of the glass tubing into the top of a one-hole rubber stopper. Slide the glass tubing until it is flush with the bottom of the stopper.

4) Cap the flask with the assembled stopper and glass tubing.

5) Slide a metal ring onto the ring stand and over the glass tubing (no need to tighten yet).

6) Insert the opposite end of the glass tubing into the base of the plastic container. Adjust the glass tubing so that the end extends several centimeters above the bottom of the container, but well below the container's rim. To prevent leakage, seal any gaps where the glass tubing and container meet with plumber's putty.

7) Place the center of the ring directly under the plastic container and tighten securely. This ring will be supporting the weight of the container and several cups of water.

8) Pour cool water into the plastic container. Fill the container with enough water so that the top of the glass tubing is a centimeter or two below the water's surface.

9) Turn on the heating element and stand back.

10) After the geyser "blows," it will reset itself by sucking the cool water from the plastic container back into the flask. Several eruptions will occur before the plastic container of water gets too hot and the temperature difference between the water in the flask and the water in the plastic container is not great enough to refill the system. When this happens, turn off or unplug the heating element and wait until the water in the plastic container cools.

From a safe distance, watch what happens as the water heats and boils.
How many different cycles can you discover in this geyser?
Use your stopwatch to time and record the duration between eruptions and any other cycles you observe.

There are three main phases to this geyser's cycle: Heating, Erupting and Refilling.

The heating time required to cause an eruption is based on two main factors: The energy output of the heat source and the length of glass tubing. The longer the glass tube, the more pressure there is on the flask of water. The more pressure there is, the more heat it takes for the water to boil and the longer it takes for the geyser to erupt.

Steam expands to over 1500 times its original volume and launches water out of the geyser (As the liquid begins to flow up the tube, it reduces the pressure in the chamber below. This in turn reduces the boiling point of the water causing a rapid conversion of liquid into steam).

After the eruption slows, a small amount of cool water in the upper container will flow down into the flask, causing the steam in the tube and flask to condense. This decreases the pressure inside the apparatus, allowing the atmosphere outside to push more water down into the flask.

Yellowstone National Park in northwestern Wyoming contains approximately 400 of the world's 700 geysers. Steamboat Geyser, located in Yellowstone's Norris Basin, is currently the world's tallest erupting geyser. Major eruptions can be over 350 feet tall.

Eric Muller (with help from Paul Doherty)



©1997 The Exploratorium, 3601 Lyon Street, San Francisco, CA 94123