Q2 — Plate boundary processes

Describe the processes occurring at a destructive plate boundary. [4]

Mark scheme (4 marks — Level-marked):

• Level 1 (1–2): basic statement that plates move together / one goes under the other.
• Level 2 (3–4): accurate use of subduction, Benioff Zone, friction, partial melting, composite volcano, deep-focus earthquakes.

Grade-9 indicative content: dense oceanic plate subducts beneath less dense continental plate at the Benioff Zone; friction triggers shallow- and deep-focus earthquakes; partial melting of subducted plate produces silica-rich, viscous magma; pressure builds beneath continental crust producing explosive composite volcanoes; ocean trench forms (e.g. Peru–Chile Trench, 8,065 m).