| San Andreas Fault, Alpine Fault |
Tectonic Clash Answer Key • Teacher Manual Page 1 of 2 • Solutions Continued on Page 2
Section B Solutions |
Page 2: 16 Points Total
3
6 Points (2 pts per case)
Case Study 1: The Afar Depression Divergent (Continental Rift)
Correct Boundary: Divergent (Continental rifting / developing ocean basin)
Accepted Tectonic Evidence: Widening rift valleys indicate tension/pull-apart motion; upwelling basaltic magma demonstrates constructive new crust creation.
Case Study 2: The Mariana Region Convergent (Ocean–Ocean Subduction)
Correct Boundary: Convergent (Oceanic–Oceanic Subduction Zone)
Accepted Tectonic Evidence: Presence of a 10,000 m trench confirms downward slab bend; sinking of dense seafloor melts asthenosphere to fuel submarine island volcanoes.
Case Study 3: The Carrizo Plain Transform (Strike-Slip Fault)
Correct Boundary: Transform (Strike-Slip / Conservative Boundary)
Accepted Tectonic Evidence: Horizontal stream offset confirms lateral shearing; absence of volcanism proves crust is neither tearing open nor plunging into mantle.
4
10 Points Total
Question 1 Solution Correct: B (2 pts)
Rationale: Transform boundaries involve lateral shearing without crustal divergence (which allows mantle decompression) or subduction (which drives flux melting). Magma rarely forms.
Question 2 Solution Correct: A (2 pts)
Rationale: Continental crust is granitic, buoyant, and thick (~2.7 g/cm³), resisting subduction into the denser asthenosphere (~3.3 g/cm³). Instead, the crust folds upward into mountains.
Question 3: Synthesis Extended Response (6 pts) Exemplar & 3-Tier Rubric
Model Exemplar Response: "Although new basaltic crust continuously forms at divergent boundaries (such as mid-ocean ridges), Earth's surface area remains constant because an equal volume of old crust is destroyed at convergent subduction zones. In subduction zones, the cold, dense oceanic lithosphere sinks back into the semi-fluid asthenosphere, where high heat and pressure cause it to melt and assimilate back into mantle convection cycles, creating a dynamic equilibrium."
Full Credit (5-6 pts)
Explains equal balance of crust formation and destruction; accurately connects subduction to recycling in the asthenosphere; uses scientific terminology.
Partial Credit (3-4 pts)
Mentions that crust gets destroyed at convergent boundaries or mentions subduction, but omits the mantle/asthenosphere role or leaves recycling vague.
Minimal Credit (1-2 pts)
States only that plates collide or move without explaining why total surface area remains constant or how crust enters the mantle.
Tectonic Clash Answer Key • Teacher Manual Page 2 of 2 • Scoring & Rubric Complete
