Teacher: One page per learner, printed A4. Sections <b>A</b> to <b>C</b> count toward <b>Written Works</b>; see <code>assessment.md</code> §1. Item <b>★</b> is the diagnostic — it asks why two convergent boundaries can build opposite things, and a learner who has memorised <i>convergent means trench</i> cannot answer it. The key below is screen-only and will not print.
A Name the boundary — apart, toward, or past — write <em>divergent</em>, <em>convergent</em> or <em>transform</em>
What is described
The boundary
A deep trench beside a chain of volcanic islands
An undersea ridge with the youngest rock at its centre
A fault with a stream bed offset sideways across it
The highest mountains on Earth, with no trench
A rift valley opening on land, with runny lava
B Fill the table — movement, structure, events — one row per boundary type
Boundary
Which way the plates move
What forms
What happens there
Divergent
Convergent
Transform
C The paper and the books — the two models from Day 1
What the paper and books did
What each one is a model of
The two boxes are the same size on purpose. Describing a model correctly and saying what it stands for are separate achievements, and the second one is the science.
D Three kinds of convergence — one line each
What is arriving
What forms
Ocean meets continent
Ocean meets ocean
Continent meets continent
★ The challenge — two convergent boundaries, two opposite results
The Andes have a trench beside them. The Himalayas do not. <b>Both are convergent boundaries.</b> Explain the difference. <span class="blank lg"></span> <span class="blank lg"></span>
What <b>one question</b> would you ask about any convergent boundary to predict which of the two it will be? <span class="blank lg"></span>
The plates move on the asthenosphere. Is the asthenosphere liquid? <span class="blank"></span> <b>How do we know?</b> <span class="blank lg"></span>
Answer key — screen only, not printed.
<b>A</b> · convergent (ocean–ocean) · divergent · transform · convergent (continent–continent) · divergent.<br><b>B</b> · <b>Divergent:</b> apart · ridge or rift valley, new crust · shallow quakes, gentle frequent eruptions. <b>Convergent:</b> toward · trench and volcanoes, <i>or</i> mountains with neither · quakes at all depths, explosive eruptions where a plate subducts. <b>Transform:</b> past · a fault, offset features, nothing built · shallow quakes, sometimes very large.<br><b>C</b> · the two sheets pushed together buckled upward with no trench — continent meeting continent; the paper slid under the book — ocean meeting continent, subduction.<br><b>D</b> · trench offshore and a volcanic mountain range inland · trench and an island arc · very high mountains, no trench, no volcanoes.<br><b>★ This is the diagnostic.</b> Item 1: the Andes have oceanic crust arriving, which is dense and subducts, so there is a trench and there are volcanoes; the Himalayas have continental crust on both sides, neither will sink, so both crumple and there is no trench. Item 2: <b>what kind of crust is on each side?</b> Item 3: <b>no</b> — S-waves cannot travel through a liquid and they cross the asthenosphere, so it is solid rock that flows. <b>A learner who answers item 1 with "one is older" or "one is bigger" has learned convergent as a single thing</b>, and that is the error this week exists to prevent.