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

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)

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.

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.

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 B. Plant matter Coal

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)

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

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)

Porphyroblasts are new metamorphic minerals that grow large crystals. 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).

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