Chapter 10
Subduction Zones
Abstract After its creation at spreading ridge axes, the oceanic lithosphere will
move with the drift of the plates until it encounters the border of another plate.
These ‘‘converging plate’’ areas are the locus of lithosphere shrinking and large
amounts of tectonic activity. During convergence, one plate may slide under
another plate; this is called ‘‘subduction’’. Subduction plates sink into the Earth’s
mantle as convergence takes place. Deep trenches, island arcs and/or high
mountain ranges mark the areas of plate convergence. Depending on the type of
rocks that have built the surface of the plates, density differences mean that some
plates will be pushed up, while others are subducted. Converging plate regions are
highly affected by earthquakes and active volcanism.
Trenches mark the boundary where tectonic plates converge and interact with each
other until one of the plates, the heaviest one, is subducted underneath the other
and plunges into the mantle (Fig. 10.1). This is called the subduction zone. During
plate convergence, the penetration of cold lithosphere into the asthenosphere
would cause heat to be conducted into the solid slab (McKenzie and Sclater 1971).
The frictional heat that is induced is sufficient to generate volcanism. Anderson
et al. (1976) have shown that heat flow profiles in the Japanese and Java trenches
reveal a thermal increase on the plate towards the arc and back arc basins. The
bending, deformation and migration of the trenches will depend on the nature of
the lithosphere (ancient vs. young) and on the velocity of plate motion. For
example, the forces acting at the trenches will have a different effect on old (stiff)
subducting plates, which will facilitate trench advance towards the back arc
regions since the stiff plates will resist bending (Lallemand et al. 2008). On the
other hand, the forces acting on the trenches, when associated with younger, more
flexible subducting plates, will move the trenches towards the open ocean.
R. Hekinian, Sea Floor Exploration, Springer Oceanography,
DOI: 10.1007/978-3-319-03203-0_10,
Ó Springer International Publishing Switzerland 2014
347
Subduction Zones
Abstract After its creation at spreading ridge axes, the oceanic lithosphere will
move with the drift of the plates until it encounters the border of another plate.
These ‘‘converging plate’’ areas are the locus of lithosphere shrinking and large
amounts of tectonic activity. During convergence, one plate may slide under
another plate; this is called ‘‘subduction’’. Subduction plates sink into the Earth’s
mantle as convergence takes place. Deep trenches, island arcs and/or high
mountain ranges mark the areas of plate convergence. Depending on the type of
rocks that have built the surface of the plates, density differences mean that some
plates will be pushed up, while others are subducted. Converging plate regions are
highly affected by earthquakes and active volcanism.
Trenches mark the boundary where tectonic plates converge and interact with each
other until one of the plates, the heaviest one, is subducted underneath the other
and plunges into the mantle (Fig. 10.1). This is called the subduction zone. During
plate convergence, the penetration of cold lithosphere into the asthenosphere
would cause heat to be conducted into the solid slab (McKenzie and Sclater 1971).
The frictional heat that is induced is sufficient to generate volcanism. Anderson
et al. (1976) have shown that heat flow profiles in the Japanese and Java trenches
reveal a thermal increase on the plate towards the arc and back arc basins. The
bending, deformation and migration of the trenches will depend on the nature of
the lithosphere (ancient vs. young) and on the velocity of plate motion. For
example, the forces acting at the trenches will have a different effect on old (stiff)
subducting plates, which will facilitate trench advance towards the back arc
regions since the stiff plates will resist bending (Lallemand et al. 2008). On the
other hand, the forces acting on the trenches, when associated with younger, more
flexible subducting plates, will move the trenches towards the open ocean.
R. Hekinian, Sea Floor Exploration, Springer Oceanography,
DOI: 10.1007/978-3-319-03203-0_10,
Ó Springer International Publishing Switzerland 2014
347