Veneer of mixed sand and gravel mantling a Saharan plain and transported originally by sheetwash and braided-stream activity. Subsequently it was weathered and modified under more arid conditions.
科学参考收录了60776条科技类词条，基本涵盖了常见科技类参考文献及英语词汇的翻译，是科学学习和研究的有利工具。