Obsidian is a glassy black igneous rock. A sample of obsidian is shown. Which type of rock forms in a similar manner as obsidian but at a slower rate?
1.schist, which forms under extreme heat and pressure
2.conglomerate, which forms when different-sized sediments cement together
3.gypsum, which forms when water evaporates and leaves behind minerals
4.granite, which forms as magma cools deep underground