A History of Agriculture in India v1.c12.7

v1.c12.7

Fig. 21. The world in the middle part of the Quaternary period. The darker areas were glaciated. The Himalayan glaciers descended into lower valleys Fig. 27. Important sites from which Palaeolithic tools have been discovered in India and Pakistan. Apart from the sites shown in this map, stone tools have been discovered from numerous other places The presence of ice in the past is inferred from the occurrence of boulder clay or glacial boulders which are often scratched and angular, the polished and striated pavements caused by the movements of glaciers over them, and the glacial moraines left behind after the recession and melting of ice. Other indicators are the U-shaped valleys carved out by glaciers, the widespread glacial debris over most of the glaciated area, the terraces formed along the banks of rivers by the fast-moving waters released from the melting glaciers, and the fluctuations in the sea-level, if not due to tectonic movements. Together with these physical evidences, the alternation of the cold-loving and warmth-loving plant and animal populations in response to climatic changes provides ancillary proofs of past glaciation.