Answer:
landward of oceanic trenches
Step-by-step explanation:
Igneous activities leads to the production of magma.
An oceanic trench is one very distinguishing feature of the deep sea. It usually lies close to subduction zones where two plates pull together. In a subduction zone, the heavier lithospheric plate usually the oceanic plate sinks beneath the lighter continental plate. The convergence of the plate leads to series of earth tectonic activities that forms the trench.
Oceanic trenches are the deepest part of the earth and they indicate the point in the oceanic plate where subduction usually sets in. Landward of the trenches is the continental plate overriding the oceanic plate. As partial melting accompanies the subducting plate, magma forces its way up to form continental igneous activities. Therefore, we can observe volcanic arcs in these zones.