Chapter review Chapter 8 - Rocks

Chapter 8.1 Review Questions Q1 Name the outer layer of the Earth CRUST Q2 Name the hot molten rock that: (a) pours out of volcanoes: LAVA (b) has not reached the surface: MAGMA Q3 Name two igneous rocks that are: (a) extrusive  BASALT, PUMICE, SCORIA, OBSIDIAN (b) intrusive  GRANITE AND DOLERITE Crust – Mantle – Outer Core – Inner Core

Chapter 8.1 Review Questions Q5 List the main characteristics of igneous rocks: interlocking crystals generally very hard and strong Q6 Define the following terms. (a) Geology  the study of rocks, their history, and the processes that form and change them (b) igneous rock  rocks formed from cooling magma or lava (c) extrusive igneous rock  igneous rocks that form on the surface of the Earth (d) lithosphere  the Earth’s outer layer of solid rock, which includes the crust and upper mantle

Chapter 8.1 Review Questions Q7 Explain how and why crystal size is affected by how fast rocks cool. Crystals that form in fast-cooling rock are often very small, and sometimes they do not form at all. Fast cooling does not give crystals enough time to grow to a large size. Slow cooling will produce larger crystals because the crystals will keep growing for longer. The liquid particles can move around, and keep adding to a nearby growing crystal. Slow-cooling rock usually has crystals large enough to see

Chapter 8.1 Review Questions Q12 Contrast the mineral composition of dark- and light-coloured igneous rocks. Dark-coloured igneous rocks usually have a high proportion of heavy minerals such as olivine that contain heavy elements like iron. Light-coloured igneous rocks tend to have a greater proportion of light elements such as aluminium and silicon. Q14 Compare the ways in which intrusive and extrusive igneous rocks form by listing their similarities and differences. Both types of rock form from magma that rises up from the mantle. Intrusive rocks form by magma cooling very slowly below the ground. Extrusive rocks form by rapid cooling of magma that reaches the surface of the crust.

Chapter 8.2 Review Questions Q1 List the main agents of: physical weathering: temperature change Water, ice and wind crystallisation of salts living plants (b) chemical weathering water acids gases

Chapter 8.2 Review Questions Q3 List the agents of erosion. Water Wind Ice Q4 Define the following terms. (a) Weathering  Weathering is the physical and chemical processes that break rocks into smaller pieces. (b) Sedimentation  Sedimentation is the process of wind or water depositing eroded rock particles.

Chapter 8.2 Review Questions Q5 Explain why igneous rocks exposed at the Earth’s surface are not identical to how they were just after they were formed. Exposed rock weathers, so the characteristics change. Q6 Explain how temperature change and water can split a rock. If the temperature changes rapidly between day and night, the rock can crack. If water enters the crack and freezes it expands, and pieces of rock can break off.

Chapter 8.2 Review Questions Q7 Explain why sediments carried by a river will be deposited when the river flows into a lake or sea. The river slows down and stops flowing when it enters a lake or sea. The particles cannot be carried unless the water is flowing, so they sink to the bottom. Q13 Compare erosion and weathering. Weathering is the breakdown of rock into smaller pieces. Erosion is what happens after weathering. Erosion is the removal of these weathered rock particles from the site where they formed.

Chapter 8.3 Review Questions Q1 Name the three main types of sedimentary rock. Clastic Chemical Organic Q3 State the general characteristics of clastic sedimentary rocks. layers like a stack of pages or books; grains do not interlock because they are cemented together; may contain fossils

Chapter 8.3 Review Questions Q4 List five sedimentary rocks and their uses. sandstone — buildings, ornamental work, paving, glass-making limestone — buildings, ornamental work, paving, glass-making gypsum — plaster-making, gardening coal — electricity generation, home heating haematite — source of iron bauxite — source of aluminium rock phosphate — plant fertiliser rock salt — table salt

Chapter 8.3 Review Questions Q5 Explain how pressure from overlying sediments contributes to the formation of clastic sedimentary rocks. Pressure from overlying sediment compresses the lower sediments and helps expel water. This allows natural cements to set and bind the rock particles together. Q6 Explain the reasons for the general characteristics of clastic sedimentary rocks. Layers — The sediments build up this way because they are deposited layer after layer. There are often time gaps in between. Grains not interlocking — The particles did not crystallise and grow together in the rock. They are cemented together. Fossils — Dead organisms often sink into sediments, especially in water, then become covered by them and are preserved when the sediments become rock.

Chapter 8.3 Review Questions Q9 Gneous rocks and chemical sedimentary rocks often have crystals in them. Distinguish between them. The crystals in igneous rocks are likely to be much harder and stronger than chemical sedimentary rocks. The igneous crystals should be interlocking, while the chemical sedimentary ones usually are. Q10 Classify each of the following sedimentary rocks as clastic, chemical or organic. (a) Mudstone – CLASTIC (b) Coal -- ORGANIC (c) Chalk -- ORGANIC (d) Gypsum -- CHEMICAL (e) Sandstone -- CLASTIC coal mudstone

Chapter 8.4 Review Questions Q1 State where metamorphic rocks form. Metamorphic rocks form where magma contacts rock below the surface. Some rocks form in the lower crust and mantle, and some form in the crust. Q2 List the two main factors involved in forming metamorphic rock. Heat and pressure

Chapter 8.4 Review Questions Q3 state the types of change that occur in rocks as they become metamorphic rock. Physical or chemical changes occur. Crystals can melt and then reform into new crystals (recrystallisation). New minerals can form. Bands can form as minerals are squashed flat under pressure and while they are hot. Q5 Outline the factors that affect the pressure acting on a metamorphic rock as it forms.

Chapter 8 Review Questions Q1 Recall how each of the main types of rocks form by matching them with the best descriptions below: igneous: volcanoes sedimentary: layers metamorphic: change Q2 Name two igneous rocks that are: (a) Intrusive -- granite, dolerite (b) Extrusive -- basalt, scoria, pumice (c) dark-coloured -- basalt, scoria, obsidian

Chapter 8 Review Questions Q5 List the general characteristics of igneous rocks. Hard and strong Interlocking crystals (if visible) Q6 Name two sedimentary rocks that are: (a) Clastic -- shale, mudstone, siltstone, sandstone (b) Chemical -- limestone, gypsum, halite (c) Organic -- coal, limestone, chalk

Chapter 8 Review Questions Q8 Choose three igneous, three metamorphic and three sedimentary rocks and state a use for each rock.

Chapter 8 Review Questions Q10 Explain the difference in crystal sizes of intrusive and extrusive igneous rocks. Extrusive igneous rocks have smaller crystals because they have cooled fast and the liquid particles cannot keep adding to the crystals. Intrusive igneous rocks have larger crystals because they cool slowly and the mineral particles can keep moving to add to the crystals which are forming. Q11 Outline the weathering processes that act on rocks. Weathering is caused by physical and chemical processes. Physical processes involve temperature change, water, ice, crystallisation of salts wind or living plants. These physically break the rock into smaller pieces. Chemical processes involve gases, water or acids. These cause the rock to crumble as the chemicals change the particles in the rock.

Chapter 8 Review Questions Q12 Describe the process of sedimentation. Sedimentation occurs where an agent of erosion (water, wind or ice) carrying rock particles meets a barrier or slows down. When this happens the particles can no longer be carried along, and they sink to the bottom or fall onto the ground and form sediments. Q13 Outline the formation of clastic sedimentary rocks. Clastic sedimentary rocks are rocks made from sediments which have been stuck together. This occurs through pressure and from substances in rocks and soil that act as natural cements.

Chapter 8 Review Questions Q16 Compare the formation of igneous, sedimentary and metamorphic rocks. The formation of igneous and metamorphic rock are similar in that both form by cooling of heated rock. Sedimentary rocks are rarely formed by heating, although chemical sedimentary rocks form by the evaporation of water from a solution. Sedimentary rocks and metamorphic rocks are similar in that they are formed under pressure. The (clastic) sedimentary rocks are formed by pressure of sediments above squashing the water out of the rock which helps the cement dry. Most metamorphic rocks form under pressure deep in the Earth. The pressure squashes the minerals into flat sheets. Igneous rocks are not formed by pressure, although pressure will affect how they cool.

Chapter 8 Review Questions Q20 (a) Construct a diagram of the rock cycle (b) Explain why it is a useful model in geology It is a useful model because it explains the endless cycle of change that rocks undergo.