Sample+Activity+writeup--Earth+Science

__ Activity 1 8/26/09 __ Sedimentary Rocks and the Geologic History of Your Community

__ TIA __ (Think About It) Sediment turns into sedimentary rock by the following steps: 1) It is __deposited__ (often by water or wind) 2) It is __compacted__ by the weight of sediments deposited on top of it 3) It is __cemented__ together with minerals leaching through the sediments, carried by groundwater

__ Part A __ 5a. The bottle of mixed sediments with water was completely clouded due to the silt. Pebbles fell to the bottom immediately After settling, the water was less cloudy. Pebbles could be seen at the bottom, surrounded by sand. A layer of sand with some silt covered the pebbles. The top layer was very fine silt.

6a. (see drawings in lab notebook of model sandstone, siltstone, rock salt, and conglomerate)

__ Part B __ 1a 1b __ Part C 1 __ a. There __are__ sedimentary rocks shown in the legend of the geologic map. These include: sandstone, siltstone, shale, conglomerate, limestone, marlstone, mudstone, coal, tuff and breccia b. The immediate area has unconsolidated deposits of sediments. The closest rocks are in the Denver formation, containing arkosic sandstone, shale, conglomerate and local coal beds. c. The oldest sedimentary rock unit on this map is the Uinta Mountain Group, which includes shale and conglomerates d. The youngest deposits are unconsolidated into rock. The youngest rocks on the map are in the Oglallah formation—cemented sand and conglomerates
 * Arkose || Rough texture, chips of clear and dark in a red background ||
 * Conglomerate || Rough texture, chips of black,brown and white in a pale or yellow/brown background ||
 * Bituminous coal || Shiny black, angular surfaces, crumbled easily ||
 * (organic) limestone || Light brown, fairly smooth texture, streaks and highlights of white ||
 * Dolomite || Pink/brown, fine texture, streaks of brown with white highlights—sharp edges and shiny surface ||
 * Rock Salt || Brownish-red, clear shiny crystal surfaces ||
 * Sandstone || Dull tan, sandy texture, dark spots ||
 * Siltstone || Pale yellow, smooth, dusty surface with rounded edges ||
 * Arkose-- clastic ||
 * Conglomerate-- clastic ||
 * Bituminous coal-- organic ||
 * (organic) limestone-- organic ||
 * Dolomite-- chemical ||
 * Rock Salt-- chemical ||
 * Sandstone-- clastic ||
 * Siltstone-- clastic ||

__ DD __ (Digging Deeper) p U8--Notes Sedimentary Rocks in the Earth’s Crust Distribution Bedrock=solid rock under soil and sediments Sedimentary rocks=rocks made of sediments—clastic, organic, and chemical—often form layers. Sediments flow downhill with flowing water Clastic sediments=rock fragments (clay, silt, sand, pebbles—from sm. to lg.) Include: Conglomerate, sandstone, siltstone, mudstone The larger the clast, the __faster__ the water needs to be to move them. Precipitation=solid chemicals come out of the water they were dissolved in. Chemical sedimentary rocks=formed by precipitation --occurs when water evaporates (hot and dry environments) Rock salt (NaCl), limestone (calcite, CaCO3), gypsum (CaSO4), dolomite (like limestone, but with Mg) Organic Sedimentary Rocks=made from living things Ex: Coal; peat --> lignite --> bituminous --> anthracite

Environments: Rocks you find __now__ indicate the past Limestone—oceans Sandstone—beaches Coal—swamps

Climate: Sandstone shows dunes (or beaches), limestone shows warm shallow (?) ocean. Coal forms with warm climates (PS Coal is found in Antarctica!)

Sediment to Rock: 1) Sediments __deposit__ by water, wind or gravity 2) Sediments are __compacted__ by sediments on top 3) Rock is __cemented__ together (by minerals) Classifying Sed. Rock: Classify as clastic, chemical, or organic Look for __type__ and __size__ of sediments that formed it. (Clues: Color and texture)

__ CYU __ (Checking Your Understanding) 1. The presence of sedimentary rocks indicates that the area may have been below sea level (Sediments move downhill) 2. Gravel is more likely to be found on a river bottom because the size of the pebbles makes it more likely to be dropped in the river than to be carried all the way to the lake 3. Limestone at the top of Mt. Everest indicates that this point was once at the bottom of an ocean. 4. Salt being found in the Great Lakes Region indicates that it was once covered by ocean, and a hotter, dryer environment caused the water to evaporate.

__U&A p U12__ 1. Chemical Sedimentary rocks are deposited by precipitation from (usually ocean) water. Clastic sedimentary rocks are formed by the deposition of sediments. Organic sedimentary rocks are formed from the bodies of once living things, usually plants. In each case: the sediments are compacted by the weight of sediments on top and then cemented together into a rock. 2.a) True—peat and coal are made from the same plants (coal is older peat) b) False—sandstone often indicates shallow water while limestone is formed in deeper water. c) True—sand is found on beaches—also in sandstone d) True—water needs to evaporate to deposit the salt e) False—clay is so small that it will be carried __beyond__ the point where water begin to slow 3.a) The photos represent: 1-conglomerate, 2-sandstone 3-siltstone b) They were formed in: 1-fast moving stream, bottom of a hill 2-shoreline 3-ocean bottom (medium depth) c) We were able to see the sediments, and identify the same sediments in the pictures.