These varieties included Norin 10 wheat and Yukara rice, which were bred by Japan in the 1950s and successfully contributed to heavier yields of tropical wheat and rice, an event called the Green Revolution. Because this was partly a product of revolutions in engineering technology and biotechnology, it can also be described as the industrialization of agriculture, which subsequently promoted the twentieth-century agricultural revolution in the world’s most industrialized nations. Because this revolution involves petroleum-dependent agriculture, flat topographical conditions have made an extremely important contribution to its progress.