Why would the gravity anomaly over a deep-ocean trench be negative?
A) because the bathymetry of the trench dips very far below sea level
B) because the crust being pulled into the trench is less dense than sediments above
C) because water fills the space above the subducting slab and is much less dense than rock
D) because the buoyant magma created at the subduction zones is less dense than the rock

Question

Quizplus · Accepted Answer

Gravity anomalies are caused by variations in the density of the Earth's crust and mantle. In the case of a deep-ocean trench, the negative gravity anomaly is due to the less-dense water-filled space above the subducting slab. This space is less dense than the surrounding rock, resulting in a gravitational pull that is weaker than expected.

Why Would the Gravity Anomaly Over a Deep-Ocean Trench Be