--- marp: true theme: default html: true --- # Quick check: sedimentary, metamorphic and the rock cycle Year 8 Earth and space · The rock cycle --- ## Today **We are learning to** a few quick questions on how sedimentary and metamorphic rocks form, how rocks change from one type to another, and why properties decide how rocks are used. Taught in class; use this to check yourself. - I can put sedimentary rock formation in order. - I can say how metamorphic rock forms and give a parent and its product. - I can trace a rock-cycle pathway and say how plate tectonics drives it. - I can link a rock property to its use. --- ## Why it matters > The same atoms have been rock, sand, mud and lava many times over. How do rocks change from one kind to another? --- ✅ Check ## The sequence **Which is the correct order for forming a sedimentary rock?** - Erosion, lithification, weathering, deposition - Deposition, weathering, lithification, erosion - Weathering, erosion and transport, deposition, lithification - Lithification, deposition, weathering, erosion * Answer: Weathering, erosion and transport, deposition, lithification --- ✅ Check ## Layers and fossils **Why are fossils found in sedimentary rock but hardly ever in igneous rock?** - Only sedimentary rock is old enough - Igneous rock is too soft - Sediment gently buries dead organisms and preserves them, while molten rock would destroy them - Fossils are made by volcanoes * Answer: Sediment gently buries dead organisms and preserves them, while molten rock would destroy them --- ✅ Check ## Properties and formation **Which sedimentary property comes from which step?** Groups: Deposition · Lithification Visible layers (strata) · Grains stuck together by cement · Sorted grains of similar size · Hardened, compacted rock * Answer: Visible layers (strata) → Deposition; Grains stuck together by cement → Lithification; Sorted grains of similar size → Deposition; Hardened, compacted rock → Lithification --- ✅ Check ## How they form **How does a metamorphic rock form?** - Rock is worn down by wind - Rock melts and then cools - Sediment settles in layers - Existing rock is changed by heat and pressure without melting * Answer: Existing rock is changed by heat and pressure without melting --- ✅ Check ## Banding **Many metamorphic rocks, such as gneiss, show bands. Why?** - They contain fossils - They were deposited in layers - Pressure in one direction squashes and lines up the minerals - They cooled quickly * Answer: Pressure in one direction squashes and lines up the minerals --- ✅ Check ## Parent and product **What does it become with heat and pressure?** Groups: Marble · Slate · Quartzite Limestone · Shale (mudstone) · Sandstone * Answer: Limestone → Marble; Shale (mudstone) → Slate; Sandstone → Quartzite --- ✅ Check ## A pathway **How could a sedimentary rock become an igneous rock?** - It is buried deep, melts into magma, then cools and crystallises - It cannot - It is weathered into sediment - It is squashed without melting * Answer: It is buried deep, melts into magma, then cools and crystallises --- ✅ Check ## How long? **Which process usually takes the longest?** - A flood carrying sand downstream - Lava cooling into basalt - Frost cracking a rock - Sandstone turning into quartzite deep underground * Answer: Sandstone turning into quartzite deep underground --- ✅ Check ## What drives it **How does plate tectonics keep the rock cycle going?** - It only affects the oceans - It buries rocks to where they melt or change, and lifts others up to be weathered - It stops rocks from melting - It makes rocks magnetic * Answer: It buries rocks to where they melt or change, and lifts others up to be weathered --- ✅ Check ## A second pathway **How could an igneous rock become a sedimentary rock?** - It melts and cools again - It is weathered and eroded into sediment, which is deposited in layers and lithified - It is heated and squashed without melting - It can't: igneous rock is too hard to change * Answer: It is weathered and eroded into sediment, which is deposited in layers and lithified --- ✅ Check ## A benchtop **Granite is used for kitchen benchtops. Why is it suitable?** - Its minerals, mainly quartz and feldspar, are hard, and slow cooling locked them into large interlocking crystals - It is made of layers - It is soft and easy to cut - It cooled quickly, so it has no crystals * Answer: Its minerals, mainly quartz and feldspar, are hard, and slow cooling locked them into large interlocking crystals --- ✅ Check ## Marble outdoors **Marble is used for statues but wears away faster outdoors in acid rain. Why?** - Rain wears every rock away at the same rate - Marble is a soft sedimentary rock - Marble is made of calcium carbonate, which reacts with acid - Marble is full of holes that let water in * Answer: Marble is made of calcium carbonate, which reacts with acid --- ✅ Check ## Choosing stone **For thousands of years Wurundjeri people quarried greenstone at Wil-im-ee Moor-ring (Mount William, Victoria) to make axe heads, which were traded across south-eastern Australia. Why choose that stone?** - Its green colour made it easy to find - It is hard and tough, with fine, tightly locked grains, so a ground edge stays sharp and doesn't shatter - It is soft, so it is quick to shape - Any nearby stone would have worked as well * Answer: It is hard and tough, with fine, tightly locked grains, so a ground edge stays sharp and doesn't shatter --- ✅ Check ## Exit ticket **Name one rock type, how it forms, and one use that depends on its properties.** * For example granite: cools slowly underground, hard interlocking crystals, benchtops.