⭐ BONUS – 🌍 Science – Earth Science: Rocks, Climate & Tectonics – Not on Level 1 Exam
ACER Level 1 · Bonus early-prep content
📋 What You’ll Learn in This Lesson
- The rock cycle and 3 rock types with formation processes
- Plate tectonics: 3 boundary types and what each produces
- Earthquakes and volcanoes: how and why they occur
- The greenhouse effect and climate science
- The water cycle and carbon cycle
⭐ BONUS – Not on ACER Level 1 Exam. Earth Science is a distinct topic within ACER Mathematical Reasoning Science from Level 2. These are questions where preparation pays off quickly.
🪨 The Three Rock Types
| Rock type |
Formation process |
Common examples |
Key features |
| Igneous |
Magma (underground) or lava (surface) cools and solidifies |
Granite (slow cooling, large crystals), Basalt (fast cooling, small crystals) |
No fossils (too hot) |
| Sedimentary |
Layers of sediment compressed and cemented over time |
Sandstone, limestone, shale, coal |
May contain fossils. Shows layering (strata). |
| Metamorphic |
Any rock changed by intense heat and/or pressure (not melting) |
Marble (from limestone), Slate (from mudstone), Quartzite (from sandstone) |
Often have banding or crystals. No fossils. |
Rock Cycle arrows: Igneous → Sedimentary (weathering + deposition). Sedimentary → Metamorphic (heat + pressure). Metamorphic → Igneous (melting). Any rock → any other rock over geological time.
🌍 Plate Tectonics – 3 Boundary Types
| Boundary type |
Movement |
What forms |
Hazards |
| Convergent (collision) |
Two plates push toward each other |
Subduction (oceanic plate goes under continental) = deep ocean trenches + volcanic arcs. Two continental plates = fold mountains (Himalayas, Andes). |
Earthquakes, volcanoes, mountain chains |
| Divergent (spreading) |
Two plates pull apart |
Mid-ocean ridges form as magma fills the gap. Rift valleys on land (East African Rift). |
Earthquakes, new ocean floor, rift valleys |
| Transform (sliding) |
Two plates slide horizontally past each other |
No crust is created or destroyed. Fault lines (San Andreas Fault, California). |
Earthquakes (often severe) |
🌋 Volcanoes – Two Types
| Type |
Lava type |
Shape |
Behaviour |
| Shield volcano |
Low viscosity (runny) basaltic lava |
Wide, gently sloping, broad shape |
Less explosive. Hawaii. |
| Stratovolcano (composite) |
High viscosity (thick) lava, gas-rich |
Steep, cone-shaped, symmetrical |
Explosive eruptions. Mt Fuji, Mt Pinatubo. |
🌡️ The Greenhouse Effect
Natural greenhouse effect (essential for life)
Greenhouse gases (CO2, H2O, CH4, N2O) in the atmosphere absorb outgoing infrared radiation from Earth’s surface and re-emit it back, keeping Earth ~33°C warmer than it would otherwise be.
Enhanced greenhouse effect (human-caused warming)
Human activities (burning fossil fuels, deforestation) increase CO2 and CH4 concentrations, trapping more heat. Global average temperature rises, causing climate change.
| Greenhouse gas |
Main human sources |
| CO2 (Carbon dioxide) |
Burning fossil fuels, deforestation, cement production |
| CH4 (Methane) |
Livestock, rice paddies, landfills, natural gas leaks |
| N2O (Nitrous oxide) |
Agricultural fertilisers, combustion |
| H2O (Water vapour) |
Natural. Amplifies other greenhouse gases. |
💧 The Water Cycle
💧 Water Cycle Process Chain
☀️ Evaporation
liquid → gas
→
☁️ Condensation
gas → droplets
→
🌧️ Precipitation
rain/snow/hail
→
🏔️ Runoff/Infiltration
to rivers/groundwater
→
💧 Collection
ocean/lakes/rivers
📝 Worked Example — Rock identification from description
Question
A geologist finds a rock with clear layering, small shell fragments embedded in it, and a rough, gritty texture. Which rock type is this?
Clue 1 – Layering (strata)
Characteristic of sedimentary rocks formed from compressed layers.
Clue 2 – Fossils (shell fragments)
Fossils only form in sedimentary rocks – other types are too hot.
Clue 3 – Gritty texture
Consistent with sandstone or shale (compacted sand/mud particles).
✅ Answer: Sedimentary rock (likely sandstone or limestone)
⭐ ACER Examiner’s Trick: ACER Earth Science questions often give you a graph of temperature and CO2 levels over thousands of years showing correlation. The question asks for a conclusion. Never say ‘CO2 causes temperature rise’ from correlation data alone – say ‘the data shows a strong positive correlation between CO2 and temperature.’
📌 Quick Reference Card — Earth Science
| Rock with fossils |
Always sedimentary. Igneous and metamorphic are too hot/altered. |
| Convergent boundary |
Plates collide → mountains OR subduction → volcanoes + trenches. |
| Transform boundary |
Plates slide past → earthquakes (no volcanoes, no mountains). |
| Shield vs composite volcano |
Shield = runny lava, gentle slopes. Composite = thick lava, explosive. |
| Greenhouse effect |
Natural = essential. Enhanced = human CO2 increase → warming. |
| Correlation vs causation |
ACER data questions: say ‘shows correlation’, not ‘proves cause’. |
