They were looking for water, but stumbled upon one of the richest shallow alluvial gold deposits ever found.他们当时在找水，却意外发现了迄今为止储量最为丰富的浅层冲积砂金矿床之一。Lowered sea levels exposed the shallow continental shelf beneath the Bering Sea.海平面下降使白令海底部的浅层大陆架暴露出来。The shallow sea bed yields up an abundance of food.浅层海底物产丰饶。