The surface of Mars : an unusual laboratory that preserves a record of catastrophic and unusual events / Mary G. Chapman -- Effect of impact cratering on the geologic evolution of Mars and implications for Earth / Nadine G. Barlow -- Megafloods and global paleoenvironmental change on Mars and Earth / Victor R. Baker -- Effects of megascale eruptions on Earth and Mars / Thorvaldur Thordarson ... [et al.] -- Terrestrial subice volcanism : landform morphology, sequence characteristics, environmental influences, and implications for candidate Mars examples / John L. Smellie -- Megascale processes : natural disasters and human behavior / Susan Werner Kieffer ... [et al.]