Unformatted text preview: a. Rapid cooling = obsidian b. Can be extrusive (volcanic) formed on surface c. Can be intrusive (plutonic) formed from magma injected into crust d. How igneous rocks help us understand prehistoric life. 3. Sedimentary rocks. Forms on earths surface, different kinds: a. Detrital SR – made up of solid particles (i.e. gravel, sand, derived from preexisting rocks) b. Chemical SR – made up of minerals in solution and extracted by inorganic or organic processes. 4. What features of sedimentary rocks can we use to understand the environment in which the sediment was deposited? a. What else can sedimentary structures be used for?...
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- Igneous rocks, Sedimentary rocks