Sparkling beaches, tidal estuaries, and granite headlands ornament the Massachusetts coast, while giant folds of gneiss and schist crisscross the interior, squeezed up between colliding continents like toothpaste from a tube. James Skehan explains the geologic history behind the rocks and landforms visible from the state's highways, including such well-known historic features as Bloody Bluff, Beacon Hill, Plymouth Rock, and Walden Pond. Interspersed through the guidebook are tales of pioneering geologists such as Harvard's Louis Agassiz, the first to propose that continental glaciers--not the remnants of Noah's Flood as early settlers had imagined--polished the state's bedrock and deposited its enormous boulders and sand plains. Numerous maps and photographs reveal ancient volcanoes, marble potholes, colorful minerals, dinosaur footprints, and America's first commercial railroad--built with blocks of Quincy granite. Geologic roadguides include tours of Boston Harbor Islands National Recreation Area, Cape Cod National Seashore, Nantucket, Martha's Vineyard, and Mount Greylock State Reservation.