what is a delta plain

http://www.answers.com/topic/delta-plain

http://images.google.com/images?hl=en&rlz=1G1GGLQ_ENUS342&q=delta+plain&um=1&ie=UTF-8&ei=iTO-SuW2M8jd8Qad5NG5AQ&sa=X&oi=image_result_group&ct=title&resnum=5