The 2022 schedule's own evidence ladder escalates through exactly these three verbs — describing the variation, then explaining the interaction, then analysing WHY it happens where it does.
What each word demands, per the schedule's own escalation
Word
What it demands
Describe
State what the variation or feature IS, with evidence — no reasons required yet.
Explain
State the mechanism connecting two processes — WHY one produces or enables the other.
Analyse (comprehensively, with insight)
Explain WHY the processes operate differently in different places or times, integrating case study evidence throughout, and ideally naming a two-way feedback loop.
✓
The schedule literally shows this progression
The 2022 marking schedule's own achievement-to-excellence ladder moves from "describes interaction between processes" (Achieved) to "explains interaction between processes" (Merit and above) — the SAME content, described at Achieved and explained at Merit, is a real, examined distinction, not a stylistic preference.
A fast self-check on command-word level
Have I stated a mechanism (WHY), not just a fact (WHAT)?
Does at least one sentence explain why the process differs BETWEEN places or times, not just that it does?
Exam-style The same fact, written at three different command-word levels Take one fact — a braided river — and write it as describe, explain, and analyse. DESCRIBE: "The Waimakariri River braids into multiple shifting channels across a wide gravel bed." EXPLAIN: "It braids because glacial and mountain erosion supply far more sediment than the river can carry at low flow, forcing it to split into multiple shallow channels rather than one deep one." ANALYSE (with insight): "The degree of braiding varies along the river's length because sediment supply and channel gradient both change from the upper catchment to the coast — braiding is most extreme where a steep, sediment-rich upper reach meets a sudden drop in gradient, exactly the pattern shown by comparing the upper Waimakariri gorge with its lower plains reach." ✓ The SAME underlying fact escalates through three genuinely different depths of treatment — this is exactly what separates Achieved, Merit and Excellence answers built on identical content.