Ch. 6 - Sedimentary & Metamorphic Rocks

1. Ch. 6 - Sedimentary & Metamorphic Rocks What are sediments? Deposits of solid material due to wind, water, ice, gravity, or chemical precipitation. Physical & chemical changes occur to produce sediments. How does this happen? Clastic sediments are rock and mineral fragments produced by weathering. Table 6-1 (pg. 122) The four main agents of erosion are wind, moving water, gravity, and glaciers. Video

2. Sediments that sink to the bottom of water are called… • Deposition or deposits • Lithification – the chemical or physical processes that transform sediments into sedimentary rocks. • 1st step to this is compaction due to lots of weight. • Open spaces may form between these compaction zones in which oil, natural gas, and water may form in these spaces. • 2nd step is cementation in which the sediments heat up the deeper they get (30° per km). • 2 types of cementation (fig. 6-5  pg. 125)

3. The term bedding refers to the horizontal layering of sedimentary rocks. • Graded bedding occurs when the particles become heavier and coarser toward the bottom layers. • Ex. Usually marine sedimentary rocks. • Cross-bedding occurs when inclined layers of sediment move forward across a horizontal surface. • Ex. Sandy beaches and sand dunes • Ex. Fig. 6-6A & 6-6B (pg.126) • Fossils are typically found in the sedimentary rocks that form in layers and other ways.

4. Types of Sedimentary Rocks • 1. Clastic Sedimentary Rocks – form from deposits of loose sediments among the Earth’s surface. • A. Course-grained  fig. 6-8 (pg. 129) • Conglomerate or breccia • B. Medium-grained • Sandstone • C. Fine-grained • Shale • 2. Chemical Sedimentary Rocks – chemical weathering causes minerals to dissolve & as the water evaporates the minerals are left behind.

5. A. Calcite  CaCO3 • Limestone • B. Halite  NaCl • Rock salt • C. Gypsum  CaSO4 • Rock gypsum • 3. Organic Sedimentary Rocks – form from the remains of once-living organisms. • A. Calcium Carbonate Shells • Limestone • B. Plant matter • Coal

6. Sedimentary Rock Uses • Oil, natural gas, coal • Uranium in sandstone • Phosphate for fertilizers • Iron for steel • Limestone used for cement, buildings, sculptors, etc. • Table 6-2 (pg. 128)

7. Metamorphic Rocks • Metamorphic rocks form at deeper depths than sedimentary rocks, which means that the temperature and pressure is greater. • Types of metamorphic rocks occur with different combinations of temperature and pressure. • Fig. 6-12 (pg. 133) • Regional metamorphism is a large region of high temperature and pressure with low grade, intermediate, and high grade regions. • Fig. 6-14 (pg. 134) • Video

8. Contact metamorphism occurs when molten rocks comes into contact with solid rock. • Hydrothermal metamorphism occurs when very hot water reacts with rock and alters its chemistry and mineralogy. • Hydrothermal fluids can dissolve some minerals, break down others, and deposit new minerals. • Metamorphic Textures • 1. Foliated – wavy layers and bands of minerals • Fig. 6-17 (pg.136) • Schist, slate, and gneiss are more of the common ones. • Fig. 6-18 (pg. 136)

9. Nonfoliated are metamorphic rocks that lack mineral grains with long axes in one direction. • Fig. 6-19 (pg. 137) • Quartzite and marble are common examples. • Porphyroblasts are new metamorphic minerals that grow large crystals. • Fig. 6-20 (pg. 137) • Most metamorphic rocks resemble their original chemical composition. • Ex. Gneiss has similar chemical compositions to its parent rock (granite).

10. Rock Cycle • This is the continuous changing and remaking of rocks. • There are several paths in the rock cycle. • The process is split into external and internal processes from igneous rocks, sedimentary rocks, and metamorphic rocks. • Fig. 6-21 (pg. 139) • Video