Guided Notes About Sedimentary Rocks

1) What are sediments, and how do they form sedimentary rocks? Sediments are pieces of solid material that have been deposited on Earth’s surface. When sediments become cemented together, they form sedimentary rocks.

2) What is chemical weathering? Chemical weathering occurs when the minerals in a rock are dissolved or otherwise chemically changed.

3) What is physical weathering? Physical weathering occurs when rock fragments break off the solid rock along fractures or grain boundaries. The minerals remain chemically unchanged.

4) Describe clastic sediment and state how it forms. Clastic sediments are produced by weathering. They have worn surfaces and rounded corners caused by physical abrasion during erosion and transport.

5) What is erosion? What are the 4 main agents of erosion? Erosion is the removal and movement of surface material from one location to another. Wind Moving water Gravity Glaciers

6) In which direction does erosion almost always carry materials? Downhill

7) What is deposition? When are sediments deposited? Deposition occurs when sediments are laid down on the ground or sink to the bottom of bodies of water. Sediments are deposited when transportation stops.

8) Why do sediments deposit in sorted layers? Faster moving water can transport larger particles. As water slows down, the largest particles settle out first, then the next-largest, so that different-sized particles are sorted into layers.

9) Which erosional forces do NOT deposit sediment in layers? Glaciers Landslides

10) What is lithification, and where does it occur? Lithification is the physical and chemical processes that transform sediments into sedimentary rocks. It occurs in sedimentary basins, where the bottom layers are subjected to increasing temperature and pressure.

11) What are the 2 steps of lithification?... Compaction—the weight of overlying sediments forces sediment grains closer together Cementation—temperatures are high enough to cause mineral growth, which cements sediment grains together into solid rock

12) Describe the 2 types of cementation. A new mineral, such as calcite or iron oxide, grows between sediment grains as dissolved minerals precipitate out of groundwater. Existing mineral grains grow larger as more of the same mineral precipitates from groundwater and crystallizes around them.

13) What determines the primary feature of sedimentary rocks? The primary feature of sedimentary rocks is bedding, which is determined by the method of transport

14) What is graded bedding, and where is it most observed? Graded bedding is bedding in which the particle sizes become progressively larger and coarser towards the bottom. It is most often observed in marine sedimentary rocks that were deposited by underwater landslides.

15) How is an organism preserved as a fossil? If an organism is buried before it decomposes and is further buried without being disturbed, then it will become a fossil.

16) What happens to a fossilized organism during lithification? During lithification, parts of the organism can be replaced by minerals and turned into rock.

17) What 3 important pieces of information do fossils provide? The types of organisms that lived in the distant past The environments that existed in the past How organisms have changed over time

18) How are sedimentary rocks classified? What are the 3 classes? Sedimentary rocks are classified by how they were formed. Clastic Chemical Organic

19) What is the difference between conglomerate and breccia? Conglomerates have rounded particles while breccias contain angular fragments of rock.

20) How and where do sandstones form? Sandstones form when sand-sized rock and mineral fragments are buried and lithified. This often occurs in stream channels, beaches, oceans and deserts.

21) What is porosity, and how does the porosity of sandstone… Porosity is the % of open space between grains in a rock. Sandstones have high porosity, which allows liquids such as water or oil to flow through them.

22) Why doesn’t shale or siltstone have high porosity? Neither shale nor siltstone have high porosity because their particles are compacted very closely together, resulting in little open space between grains.

23) What are evaporates, and how do they form? Evaporates are the layers of chemical sedimentary rocks that result when minerals precipitate out of saturated bodies of water.

24) How does limestone form from ocean animals? Some ocean animals use calcium carbonate dissolved in seawater to make their shells. When these animals die, their shells settle to the bottom and form thick layers of calcite, which is buried and lithified to form limestone.

25) How does coal form? Coal forms when thick layers of vegetation slowly accumulate in swamps or coastal areas. This plant material is slowly buried and compressed, which lithifies it into coal.

26) List the major resources provided by sandstone and limestone Sandstone: uranium, oil, natural gas, groundwater, building materials Limestone: cement materials, blocks for construction phosphate