Rocks, tectonics and changing landscapes
Connect geological processes with evidence while distinguishing movement, breakdown and transport.
What you will tackle
- Classify rocks and minerals from properties
- Relate plate boundaries to earthquakes and volcanoes
- Distinguish weathering, erosion and mass movement
- Evaluate distributions and geological-process evidence
Materials record processes
Minerals have characteristic compositions and structures; rocks are aggregates of one or more minerals or other material. Hardness describes scratch resistance, streak is the colour of a mineral's powder, and cleavage is a tendency to break along particular flat planes. Combine properties to compare candidates; one property rarely identifies a real mineral uniquely. The candidate-property table below is an invented classification model. Igneous rocks form from cooling melt, sedimentary rocks from deposited material and lithification, and metamorphic rocks from change under heat/pressure without complete melting. Weathering breaks material down in place; erosion removes/transports it. A rock cycle describes possible transformations rather than one compulsory sequence.
Motion at different scales
Moving plates can diverge, converge or slide past one another. Their boundary processes help explain concentrated earthquakes, some volcanic activity and mountain building; not every boundary has every feature. Earthquakes involve sudden fault movement and released energy; volcanoes involve magma reaching the surface. Mass movements move slope material mainly under gravity; water, slope angle and material strength can influence stability.
| Candidate | Hardness | Streak | Cleavage |
|---|---|---|---|
| A | 2 | White | Flat planes |
| B | 4 | Dark | Flat planes |
| C | 7 | White | No flat planes |
Build your notes, then practise
Work on paper before opening an explanation. Guided tasks provide a starting point; independent tasks remove the scaffolding; application tasks ask you to justify a method or interpretation in context.
Guided practice
Guided 1
Classify cooled lava, compacted sandstone and rock altered by heat without melting. Distinguish a boulder cracking in place from fragments carried downstream. A map clusters earthquakes along a narrow belt: what plate-related hypothesis does it support?
Show a starting hint
Separate the material description from the process inferred.
Compare with the explained answer
- The examples are igneous, sedimentary and metamorphic respectively.
- Cracking in place is weathering; downstream transport is erosion.
- A plate-boundary hypothesis fits a concentrated earthquake belt, but mapping alone does not specify every boundary process.
Answer / response criteria: Igneous, sedimentary, metamorphic; weathering versus erosion; a qualified boundary hypothesis.
Guided 2
Use the supplied invented mineral-candidate table: A hardness2/white streak/flat cleavage, B hardness4/dark streak/flat cleavage, C hardness7/white streak/no flat cleavage. An unknown scratches a hardness3 reference but not a hardness5 reference and has a dark streak. Which listed candidate fits?
Compare with the explained answer
- Under the supplied scratch rule, its hardness exceeds3 but does not exceed5.
- Only candidate B's hardness4 lies in that range, and B also matches the dark streak.
- This identifies B within the limited supplied candidate set; it does not uniquely identify a named real mineral.
Answer / response criteria: Candidate B within the supplied model.
Independent practice
Independent 1
A supplied model says plates move apart at Boundary A and slide past at B. Which is divergent and which transform? Why need earthquakes at B not imply a volcano? Predict how added water could increase a loose slope's movement risk without making it certain.
Compare with the explained answer
- A is divergent and B is transform in the supplied model.
- Fault movement releases seismic energy without requiring magma to reach the surface.
- Water can add weight or reduce friction/strength; the result also depends on drainage, material and slope geometry.
Answer / response criteria: A divergent, B transform; earthquake and magma processes differ; risk depends on stated slope conditions.
Independent 2
An unknown in the same supplied model scratches a hardness5 reference, has a white streak and shows no flat cleavage planes. Which candidate fits? Could white streak alone distinguish A from C?
Compare with the explained answer
- Scratching the hardness5 reference requires a higher hardness under the stated model.
- C has hardness7 and matches white streak with no flat cleavage.
- A and C both have white streaks, so streak alone cannot distinguish them.
Answer / response criteria: Candidate C; white streak alone is insufficient.
Application practice
Application 1
A claim says a sedimentary rock can become igneous simply through pressure with no melting. Assess it. A valley contains rounded transported stones beside fractured bedrock: propose evidence for both weathering and erosion. Design a comparison to test water's role in mass movement.
Compare with the explained answer
- Igneous formation requires melt cooling; pressure without complete melting can instead contribute to metamorphism.
- Fractured bedrock can indicate breakdown in place; transported/rounded material supports transport and abrasion, with context needed.
- Compare matched slope angle and material with controlled water conditions, repeated measurements and recorded movement; use an appropriate supervised model rather than an unsafe real slope.
Answer / response criteria: The rock claim omits melting; distinguish in-place breakdown from transport; use controlled comparisons for slope movement.
Application 2
A report identifies a real mineral solely because it scratched one reference object. Explain why this overstates the supplied candidate exercise. Propose further non-destructive observations and distinguish mineral identification from calling a rock igneous.
Compare with the explained answer
- A scratch comparison supplies a hardness constraint, not a unique composition or structure; many real minerals can share a hardness range.
- Compare existing streak records, cleavage/fracture appearance and other supplied physical observations without performing an unsupervised test.
- Igneous describes a rock's formation from cooling melt; it is a rock-process classification, not the identification of a single mineral.
Answer / response criteria: Use multiple properties and a stated candidate set; rock origin and mineral identity are distinct questions.
What can you explain now?
A report identifies a real mineral solely because it scratched one reference object. Explain why this overstates the supplied candidate exercise. Propose further non-destructive observations and distinguish mineral identification from calling a rock igneous.
Compare with the explanation
Use multiple properties and a stated candidate set; rock origin and mineral identity are distinct questions.
Explain the reasoning before comparing. This review records your self-assessment rather than an official score or mastery decision.
After trying it yourself, choose your next review. This is your self-assessment.
Your review choice appears on Today. Sign in to sync it across devices.
Source and review status
Coverage follows the named requirements and examples in the 2026–2027 ACT test guide and subject descriptions. That guide explicitly does not list every possible topic. The broader coded College and Career Readiness Standards are also mapped to conceptual teaching and practice; this does not calibrate a learner to a score band. The separate scientific-background context list and reading-complexity rubric have their own stated limits.
Original teaching and explained self-check practice are available. Specialist review and difficulty calibration remain pending. Essays require self-check or teacher review and are not automatically marked or awarded official scores.
Official source specification / guide