This book presents the basic physics needed to model the past, present and future of large continental ice sheets. Minimal mathematical ability is needed. Simple triangles and rectangles allow a visual treatment of the force balance for stresses driving and opposing glacier flow. The holistic aspect of the book recognises that ice flow in ice sheets begins as slow sheet flow from high convex ice domes near the centre of an ice sheet, with most sheet flow converging on fast concave currents of ice called ice streams near the ice-sheet margin, and ends as relatively thin and flat shelves of ice floating in water or lobes of ice grounded on land.