1. Chapter 3 - Rocks Notes January 2013

2. 3-1 What are rocks? Rocks in Earth’s Crust 1.Petrologists study rocks & minerals. 2.Rocks are made of minerals (2000). Classification of Rocks 1.Classification is the grouping of things that are alike. 2.Petrologists classify rocks & minerals. Classes of Rocks 1.Petrologists classify rocks by the way they form. 2.The THREE classes of rocks are: igneous, sedimentary, and metamorphic.

3. Section 3-2 How are igneous rocks formed? Heat Inside Earth 1.The deeper you dig, the hotter it gets 2.Molten rock is made of melted minerals. Magma and Igneous Rock 1.When molten rock cools and hardens, igneous rock is formed. 2.Igneous rock can take thousands of years to form from magma inside Earth. Lava and Igneous Rock 1.Igneous rocks form quickly from lava above Earth’s crust.

4. Section 3-3 How are igneous rocks classified? A Combination of Minerals 1.The SIX most common minerals in igneous rocks are Quartz, Mica, Amphibole, Feldspar, Olivine, & Pyroxene Crystal Size 1.Crystal size depends on the amount of time it takes the molten rock to cool. 2.Magma = large crystals; Lava = small or none Texture 1.Texture can be used to identify rocks. 2.Large crystals are coarse; small crystals are fine; no crystals are glassy

5. 3-4 How are sedimentary rocks formed? Sediments 1.The heaviest sediment sinks first. Natural Cement 1.As more layers form, water is squeezed out. 2.Dissolved minerals act as cement. Sedimentary Rock From Living Things 1.Rock can be formed from the remains of living things.

6. 3-5 Classifying Sedimentary rocks Groups of Sedimentary Rocks 1. Clastic rocks are made from rock particles. 2. Nonclastic rocks are made from dissolved minerals or the remains of living things. Particle Size 1. Sandstone and Shale are clastic rocks Dissolved Minerals 1. Limestone and halite are nonclastic rocks. Plants and Animals 1. Coals are nonclastic rocks formed from the remains of plants.

7. 3-6 How are metamorphic rocks formed? Changed Rocks 1. Heat & pressure inside Earth change rocks over time. Heat and Pressure 1.Too much heat will melt a rock or mineral. 2. Extreme pressure will cause flattening (layers). Magma 1. All rock types can be changed into metamorphic rocks.

8. 3-7 How are metamorphic rocks classified? Classifying Metamorphic Rocks 1. Metamorphic Rocks can be foliated or nonfoliated depending on their mineral crystal bands. Banded Metamorphic Rocks 1. Foliated rocks have crystals arranged in bands. 2. Gniess (from granite) and schist (from shale) are examples of foliated rocks. Metamorphic Rocks Without Bands 1. Nonfoliated do not have minerals arranged in bands. 2. Quartzite is an example (from sandstone).