The biggest volcano in the Solar System, Mars' Olympus Mons, stands 26 km (16 miles) high and is 600 km (375 miles)
across-dwarfing even Earth's largest volcano, Mauna Kea, and rising three times as high as Mt. Everest. This
experiment will show you how Olympus Mons got so big.
- Label one piece of posterboard "Olympus Mons" and the other "Mauna Kea".
- On "Olympus Mons" use the compass to draw a circle 30 cm (12 inches) in diameter. Draw another circle on "Mauna Kea" 10cm (4 inches) in diameter.
- Cut a half inch wide strip off of the long edge of the index card. Cut the strip in half, and tape one half to each circle's center, so that each strip stands upright right in the middle. Trim the strips so that the "Olympus Mons" strip stands 12mm (one-half inch) high, and the "Mauna Kea" strip stands 5mm (one-quarter inch) high.
- Use the plaster of paris to make your volcanoes, spreading out the plaster to match the height of each strip and diameter of the circles. Spray water onto the volcanoes to keep them damp while you work on them.
- Once dry, you can paint Olympus Mons and Mauna Kea to look like the real volcanoes.
- Weigh each volcano.
- Compare the heights, diameters and weights of the two volcanoes.
Many scientists believe that Olympus Mons last spouted lava an estimated 100 million years ago. All that lava
flowed up through the Martian crust and out and over the lava from previous eruptions - to the edges of the
enormous mountain. All that lava has nowhere else to go. On Earth, however, volcanoes sometimes form on the
edges of moving parts of the Earth's crust called tectonic plates. The movement of the plates pulls away some
of the mass of lava around volcanoes, limiting how high they can grow!