Std 3c. Know how to explain the properties of rocks based on the physical and chemical conditions in which they formed, including plate tectonic processes Obj: Explain how sedimentary rocks form, the subclasses, and give examples of each Obj: Explain how metamorphic rocks form, the subclasses, and give examples of each

III. Sedimentary rocks A. Sediment - loose fragments of rock, minerals, + organic materials 1. Characteristics determined by who moves it, how far + how fast it moves 2. 4 main agents of transport - water, ice, wind, gravity a. Wind + water tend to sort by size 3. Well-sorted - all grains are roughly the same size/shape 4. Poorly sorted - many different sizes/shapes 5. The farther sediment travels from its source, the finer + smoother particles become

Decreasing particle size

B. 2 main processes convert sediment into sedimentary rock 1. Compaction - sediment crushed by weight of overlying sediments as it is buried beneath other sediments 2. Cementation - minerals settle into tiny spaces between sediment grains + glue them together C. Stratification - layering of sedimentary rock, also called beds 1. Vary in thickness + composition

Close up of sedimentary rock

Stratification

D. 3 classes 1. Classified by how they form + what they are made of 2. Chemical - water evaporates leaving dissolved minerals behind or concentration of minerals in water too high and some precipitate out of water a. Evaporite - forms from evaporation ex: gypsum, halite

3. Organic - squished remains of plants or animals or their shells ex: coal, limestone

Gypsum - evaporite Gypsum made of sulfate, formed as result of evaporating sea water in massive prehistoric basins. Very soft, used to make Plaster of Paris, casts, molds + wallboards. Limestone - organic Limestone made from calcite which came from beds of evaporated seas + lakes + from sea animal shells. Used in concrete + an excellent building stone for humid regions.

4. Clastic - fragments of preexisting rocks are compacted or cemented together a. Classified by size of sediments they contain b. Conglomerate contains large, rounded pieces c. Breccia contains large, angular pieces Ex: Sandstone composed of sand-sized grains Shale composed of clay-sized particles

Conglomerate - clastic Conglomerate is made up of large sediments like sand + pebbles. The sediment is so large pressure alone cannot hold rock together; it is also cemented together with dissolved minerals. Shale - clastic Shale formed from clay compacted together by pressure. Used to make bricks + other material fired in a kiln.

IV. Metamorphic rocks A. Metamorphism – process where heat, pressure, + hot fluids cause some minerals to change into other minerals 1. Minerals may change size or shape, or may separate into parallel bands giving rock a layered appearance 2. Hot fluids may circulate through rock, changing the mineral composition by dissolving some materials or adding others

3. 2 types of metamorphism a. Contact - contact with magma b. Regional – change over a large area, often a result of tectonic forces

B. 2 classes 1. Foliated – minerals arranged in bands or layers Ex: slate, schist, gneiss 2. Nonfoliated– no bands or layers of minerals a. Often made of only one or two minerals or of round or square grains which don’t line up well Ex: marble, quartzite

Gneiss - foliated Gneiss may have been granite, which is igneous, but heat + pressure changed it. You can see how mineral grains in the rock were flattened through tremendous heat + pressure + are arranged in alternating patterns. Schist - foliated Schist can be formed from basalt, an igneous rock; shale, a sedimentary rock; or slate, a metamorphic rock. Through tremendous heat + pressure, these rocks were transformed into this new kind of rock.

Marble - nonfoliated