Earth and Rock Cycle Cheat Sheet

Name:

Date:

🌏 Earth’s Layers and Geological Time

Crust: The thin, solid outer layer made of rock. It is about 5–70 km thick and is thickest beneath continents.

Mantle: The thickest layer, made of solid and partly molten rock. Mantle material can move slowly because of heat.

Outer core: A liquid mixture mainly of iron and nickel. Its movement helps generate Earth’s magnetic field.

Inner core: A solid mixture mainly of iron and nickel. Extreme pressure keeps it solid, even at very high temperatures.

Memory cue: C-M-O-I = Crust, Mantle, Outer core, Inner core.

With increasing depth: Temperature and pressure generally increase. Pressure is caused by the weight of the material above.

Geological time: Earth’s history is divided into very long intervals called eons, eras and periods. Relative dating compares the ages of rocks and layers rather than giving an exact numerical age.

Law of superposition: In undisturbed sedimentary layers, lower layers are generally older than the layers above them. Folding, faulting, erosion or volcanic activity can disturb this order.

1. Match each Earth layer with its key description by writing the correct layer name.

Solid iron–nickel centre: ____________________

Liquid iron–nickel layer: ____________________

Thin outer rock layer: ____________________

Thick layer of hot rock: ____________________

2. Describe how temperature and pressure change as depth below Earth’s surface increases.

🪨 Rocks and the Rock Cycle

Igneous rocks: Form when magma or lava cools and crystallises. They are often hard and may contain visible crystals. Examples include granite and basalt. Uses include building stone, roads and kitchen benches.

Sedimentary rocks: Form when sediment is deposited, then compacted and cemented. They commonly have layers and may contain fossils. Examples include sandstone, shale and limestone. Uses include building materials, cement and some sources of fossil fuels.

Metamorphic rocks: Form when existing rock is changed by heat and pressure without melting. They may have bands, flattened crystals or a new texture. Examples include marble and slate. Uses include tiles, roofing and sculptures.

Magma is molten rock below Earth’s surface. Lava is molten rock that reaches the surface.

Key processes: Weathering and erosion break down and move rock. Deposition drops sediment. Compaction and cementation form sedimentary rock. Cooling and crystallisation form igneous rock. Heat and pressure cause metamorphism. Melting forms magma.

Rock-cycle flow diagram:

Existing rock → weathering and erosion → sediment → deposition, compaction and cementation → sedimentary rock

Any rock → heat and pressure → metamorphic rock → melting → magma

Magma → cooling and crystallisation → igneous rock

The arrows can go in many directions. The rock cycle is not a one-way process: any rock type can be changed into another through different processes.

3. Choose the correct answer: Which process forms an igneous rock?

Compaction and cementation

Cooling and crystallisation

Weathering and erosion

Heat and pressure without melting

4. Explain why the rock cycle is described as non-linear. Include one example of a possible pathway.

5. Complete the sentence: Molten rock below Earth’s surface is called ____________, while molten rock at the surface is called ____________.

🔎 Apply Your Knowledge: Hazards and Rock Identification

Natural hazards: A landslide is the rapid movement of rock, soil or debris down a slope. A lahar is a fast-moving volcanic mudflow containing water, ash, mud and rock. Both can transport and deposit sediment.

6. A lahar leaves a layer of mud and rock, and sedimentary layers are later deposited above it. Which layer is generally older, and why?

7. Observe a rock sample and record useful evidence.

Colour: ____________________ Grain or crystal size: ____________________

Layers or bands: ____________________ Texture: ____________________

Hardness: ____________________ Fossils: ____________________

Holes or vesicles: ____________________

8. Use your observations to suggest a rock type and justify your choice.

Sentence starters for strong explanations

“The rock’s __________ property suggests it formed when __________.”

“Because this rock has __________, it is likely to be __________ rock.”

“Its formation explains its use because __________.”

“The rock is suitable for __________ because it is __________.”

Remember: Link formation → properties → use. For example, slow cooling can produce large crystals, which may make a rock strong and useful as a building material.

Australian Curriculum: AC9S8U04