Observations and results
Could your geodesic dome easily support your hand as you pressed it down on the dome, even when you increased the pressure?
A geodesic dome's design allows it to support a surprisingly large amount of mass compared with the structure's mass itself. Because of this you should have seen that the geodesic dome could easily support your hand as you pressed down on the top of the dome, even when you increased the pressure a little. You would need to apply a lot of pressure before the dome would fail. The struts of a geodesic dome—made here by toothpicks—are arranged to make triangles, which overall create a rigid network that disperses any stress forces applied to the top of the dome through the rest of the structure.
Because the geodesic dome approximates a sphere, it has a relatively low surface-area-to-volume ratio (that is, its volume is relatively large compared with its surface area) and it can enclose a large amount of volume when compared with the mass of the structure itself.
More to explore
Chapter 9: Mathematics, Geodesic Dome, from Science Toys
Dome Basics, from Building Big, PBS Online
Fun, Science Activities for You and Your Family, from Science Buddies
Dome Sweet Dome, from Science Buddies