In this region, the north-south trending ridges on the seafloor
represent a divergent boundary. Volcanism along this ridge
is quiet and relatively frequent. An increase in water temperature,
detected by underwater instruments, or a series of small earthquakes
is often the only evidence that an eruption has occurred along
this mid-ocean ridge.
The line connecting sections of the divergent boundary is
a transform boundary. Visualize the plate on the north side
of this line moving east compared to the plate on the south
side of the boundary.
The deep trench parallel to the coastline is a subduction
zone, where the plate on the left dives below the one on the
right. Magma is generated east of the subduction zone, where
subducted material reaches a depth at which it melts. Eruptions
of subduction-related volcanoes are not very frequent, but
when they do occur, they are very explosive.
! Follow the instructions on the left to examine these features
in three dimensions.