Modeling volcanoes

From: "Gloria D. Rall" <>
Subject: Modeling volcanoes
Date: Fri, 11 Jul 1997 20:09:21 -0700

We have been experimenting a lot with modeling volcanoes and we
thought you might like to know what we've learned.  We make our
volcanoes with clay and with shallow craters.  We give the
students a very good picture of Olympus mons that really shows
the shape of the volcano in a close-up view, and ask them to make
the models as realistic as possible.  That works fine, but we
were unhappy with getting it to erupt.  We used vinegar and
baking soda.  It works well but the action is much more like an
eruptive volcano.  Olympus mons is a shield volcano where the
lava gently bubbled over the sides to give that gentle slope.  We
discovered that a tablespoon of water, enough cornstarch to
thicken it, and an Alka Seltzer tablet works well. This bubbles
like a shield volcano and the "lava" just spills over the sides.
We add food coloring to make it more realistic.  The cornstarch
hardens rapidly, and if you do this several times you can see how
the volcano shapes itself somewhat like Olympus mons.