stratigraphy geology

例句：

1. 1. The study of rocks and their layers is called stratigraphy.
   研究岩石及其层次被称为地层学。
2. 2. This fossil record tells us about the history of life on Earth.
   这个化石记录告诉我们地球上生命的历程。
3. 3. Geologists use tools to study the layers of rock in a region.
   地质学家使用工具来研究一个地区的岩石层次。