1Geology 200, Questions for Test 2, November 8, 2007 Matching: what type of rocks or sediments would you most likely find in each of the following environments? Use each answer only once. Matching: write the correct letter next to each term (1 pt. Each) Use each answer only once. 1. Fluvial/stream ____ A. limestone with large fossils 2. Regolith ____ B. associated with freeze/thaw 3. eolian ____ C. unsorted clastic sediments 4. barrier island ____ D. thick, cross-bedded sandstones 5. A horizon ____ E. decayed rock 6. glacial ____ F. well-sorted, flat sandstones 7. alluvial fan ____ G. coal 8. Wedging ____ H. topsoil 9. lagoon or swamp ____ I. conglomerate and breccia 10. organic reef ____ J. cross-bedded channel sandstones Explain why joints are important in weathering processes. How does soil originate? Describe how it forms. Why are mudrocks the most common sedimentary rocks? (Hint: think of weathering products.) Why is quartz sand so abundant in clastic sedimentary rocks? (Hint: think of weathering products.) Put these rock types in the order (starting with 1) by which they would weather the fastest: ____ Granite ____ Rock salt ____ Gabbro ____ Sandstone ____ Schist ____ Shale ____ Gypsum Which rock type would weather to form the most clay? A. limestone B. granite C. basalt D. sandstone Which of the following rocks would be most susceptible to chemical weathering? A. sandstone B. slate C. granite D. shale E. limestone Chemical weathering would progress most rapidly in: A. Colorado B. Brazil C. West Virginia D. Greenland Ice wedging is important in preparing rocks for chemical weathering because it: A. keeps rocks from moving down slope B. produces swelling as certain minerals are altered to clay C. enlarges fractures and cracks, thereby increasing the surface area of the rock D. reduces the rock to its constituent minerals2Ice wedging would be most effective in: A. permafrost areas of Alaska B. areas where freezing and thawing occur many times a year C. areas beneath the glaciers in Greenland D. latitudes where strong heating occurs Which of the following minerals is most resistant to chemical weathering: A. plagioclase B. quartz C. olivine D. amphibole Which of the following rock-forming minerals weathers to form most of the clay found in soils? A. quartz B. olivine C. mica D. feldspar The general term for the blanket of loose rock debris that covers large areas of the Earth’s surface is A. regolith B. bedrock C. outcrop D. laterite A talus accumulation consists largely of: A. soil B. a mixture of silt and ice C. alternating layers of clay and sand D. coarse, angular rock fragments Physical weathering would progress most rapidly in: A. the Rocky Mountains B. Brazil C. West Virginia D. Antarctica Which of the following minerals is most stable at Earth’s surface? A. plagioclase feldspar B. olivine C. pyroxene D. hematite The products of ice wedging often accumulate at the base of cliffs to form piles of angular rock fragments called: A. soil B. talus C. bedrock D. exfoliation domes Which environment has the strongest chemical weathering? A. Polar climates B. Temperate climates C. Deserts D. Tropical climates Because of differential weathering, most of the ridges of the Appalachians are capped by what type of sedimentary rock? Which of the following is the most effective process of physical weathering. A. Ice wedging B. Exfoliation C. Thermal expansion and contraction D. Plant roots3 What are the two most important variables in chemical weathering? (2 pts.) ___________________________ ________________________________ Where are the two regions on the Earth where the thickest regolith be found? (2 pts.) ___________________________ ________________________________ This chemical reaction: 2Fe2SiO4 + 4H2O + O2 = 2Fe2O3 + 2H4SiO4, is an example of: A. dissolution B. hydration C. oxidation The susceptibility of weathering of silicate rocks follows the same path as ___________________________________. (2 pts.) Which of the following elements are concentrated in clays during chemical weathering: A. Ca and K B. Na and Mg C. Fe and Mn D. Al and Si The zone of accumulation is called the ____ horizon of the soil/regolith. Ions of which element are most readily carried by river water to the ocean? A. Fe B. Al C. Ca D. Si Where do laterites occur, and what is their composition? What is the principal cause of grain-size variations in clastic sedimentary rocks? In which environment are graded beds most likely to form? E. delta F. beach G. continental slope H. tidal flat What are the two major categories of sedimentary rocks? _______________________________ _______________________________ Give two examples of each type and indicate which category they belong in. What is the difference between a breccia and a conglomerate? What is the upper size limit of sand grains? A. 1/8 mm B. 1/2 mm C. 2 mm D. 4 mm4What is the lower size limit for boulders? A. 6 inches B. One foot C. Three feet D. 10 feet Which of the following is texturally most similar to sandstone? A. gypsum B. fossiliferous limestone C. carbonate grainstone D. carbonate mudstone The most universal feature of sedimentary rocks is: A. cementing material B. uniform grain size C. fossils D. stratification Which of the following would a geologist call a formation? A. a distinctive layer of sedimentary or volcanic rock B. a unique landscape feature such as a steep spire C. a stalactite in a cave D. a naturally formed staircase up a cliff of sedimentary rock A sedimentary rock formed of clastic particles derived from weathering and erosion of rocks is: A. gypsum B. rock salt C. limestone D. chert E. sandstone Which of the following is the most abundant nonclastic rock? A. limestone B. rock salt C. gypsum D. drip stone in caves A clastic sedimentary rock composed of rounded to subrounded gravel is called a: A. breccia B. conglomerate C. sandstone D. siltstone Transportation and deposition of sediment by turbidity currents is commonly indicated by: A. mud cracks B. cross bedding C. ripple marks D. graded bedding E. horizontal layers In graded bedding, the size of the sediment particles in a single layer: A. is uniform from top to bottom B. ranges from coarsest at the top to finest at the