Teased by his friends for having an imaginary playmate, Chad tries to bid Pingo farewell but Pingo refuses to leave.

When Chad and his friends hold a competition to see whose imaginary friend is the best, the schoolyard bully says his is the best, but in the end everyone learn

Geomorphology, the discipline which analyzes the history and nature of the earth's surface, deals with the landforms produced by erosion, weathering, deposition

Plate tectonics - Earthquakes and volcanoes - Weathering and slopes - Glaciation - Coasts - Deserts - Weather and climate - Soils - Biogepgraphy - Population -

The seven volumes in this series contain reproductions of papers that the individual editors regarded as the initiators of critical concepts in geomorphology.