Chunks of the overlying rock may break off and become a part of a sill. 上復岩石的碎塊可能破裂並成為岩床的一部分。
In fact, this period of Canada's underground rock Chuangpi area of great scientists of the Earth's surface known as the oldest known. 事實上,加拿大的這段地下面積很大的岩床被科學家稱之為地球表面已知的最古老的地方。