Igneous rocks:
1. Basalt: A dark, fine-grained volcanic rock formed from the rapid cooling of lava on the Earth's surface.
2. Granite: A light-colored, coarse-grained intrusive rock formed from the slow cooling of magma beneath the Earth's surface.
3. Rhyolite: A light-colored, fine-grained volcanic rock formed from the rapid cooling of lava on the Earth's surface.
Sedimentary rocks:
1. Sandstone: A rock composed of sand grains that have been cemented together over time.
2. Limestone: A rock composed mainly of calcium carbonate (CaCO3), which is formed from the accumulation and compaction of marine organisms such as corals and shellfish.
3. Shale: A fine-grained sedimentary rock composed of clay minerals that are formed from the compaction and cementation of mud.
4. Coal: A black or brown sedimentary rock formed from the accumulation and compaction of plant matter, which has been subjected to heat and pressure over time.
Metamorphic rocks:
1. Marble: A metamorphic rock formed from the recrystallization of limestone under high temperature and pressure.
2. Slate: A fine-grained metamorphic rock formed from the recrystallization of shale under high temperature and pressure.
3. Gneiss: A coarse-grained metamorphic rock formed from the recrystallization of igneous or sedimentary rocks under high temperature and pressure.
These are just a few examples of rock layers, and there are many other types that can be found in different geological settings around the world. The study of rock layers, known as stratigraphy, helps geologists understand the history of the Earth and the forces that have shaped it over time.