4. Obsidian - rapid cooling when lava flows into water.
Granite - very slow cooling such as what occurs when magma is trapped beneath Earth's surface.
Basalt - cooling when lava flows over land
5. They are slightly simplistic and rock formation is not limited to only these methods.
6. They give a general overview of how a certain type of rock may be formed and how to identify them from a basic level based on their location.