Volcanology of Mars through the crust to produce volcanic mountains. However, the largest volcano on the planet, Olympus Mons, is thought to have formed when the plates were not moving. Olympus Mons may have formed just after the plate motion stopped. The mare-like plains on Mars are roughly 3 to 3.5 billion years old. The giant shield volcanoes are younger, formed between 1 and 2 billion years ago. Olympus Mons may be "as young as 200 million years." Norman H. Sleep, professor of geophysics at Stanford University, described how the three volcanoes that form a line along the Tharsis Ridge may be extinct
The Angry Red Planet find a recording of an alien voice, which announces that the ship's crew were allowed to leave Mars so they could deliver a message to their home planet. The voice then states that "we of Mars" have been observing human development on Earth for many thousands of years and have determined that humanity's technology has far outpaced progress in cultural advancement. The alien then accuses humankind of invading Mars, warning that if future expeditions ever return to the Red Planet, the Earth would be destroyed in retaliation. "The Angry Red Planet" began as "The Planet Mars", a treatment written by