沙砾覆于铁质土层与砂砾层之上.Gravelly - sand over an iron - pan and gravel layer.小石头、砂砾层也可用来做隔绝层,以保持水分,降低土壤的温度.Pebbles and gravel also insulate the soil to keep surface temperatures low and preserve water.古河谷的边缘地带,往往缺失底部的河床相砂砾层.The ed...
在多西特海岸的岩石上,就可以看到数以千计的菊石.Thousands of these can be seen in the rocks on Dorset Coast.随着小菊石的生长,它会长出新的腔,然后将原来的腔封闭起来.As the young grew larger it grew a new chamber and sealed off the previous one....