ฉันแปลประโยคยาวๆไม่ค่อยออก..ROCKS THAT COME INTO CONTACT with the atmosphere and with water are gradually weathered (pp.50-51) , even the hard lavas and granite. Water seeps in between the mineral grains and chemically reacts with the rock to break it down. Particles of the weathered rock are removed by falling rain, or are blown away by the wind and dropped elsewhere. In the new location, layers of sedimentb are formed, which may become buried by more and more layers. These layers may also contain organic material such as plants and the remains of dead creatures. Eventually the sediments harden and become compacted. Ground water percolates through the sediment, leaving behind minerals which cement the sediment grains together. In this way the sediment is lithified (becomes rock). By understanding how modern sediment forms, it is possible to reconstruct the environment of times gone by - the palaeoenvironment - and to make palaeogeographic maps showing the geography of land masses that existed many millions of years ago.ต้องใช้เวลา..เพราะฉันไม่เก่งภาษาอังกฤษ