Ace the IGCSE Environmental Management Test 2026 – Dive In and Green Your Future!

In subduction zones, earthquakes occur along the plane where the sinking plate fits into the mantle, tracing a dipping sheet of seismic activity. This pattern is known as the Benioff zone (also called the Wadati–Benioff zone). It reveals the depth range of earthquakes within the down-going slab, from near the trench down into deeper depths, so mentioning the “upper portion” points to the shallower part of that dipping zone. The term Benioff zone is the correct label for this seismic pattern. The other options aren’t related to earthquake zones: basalt is a rock type, bioethanol is a fuel, and arable farming is agricultural practice.