1. What is the nature of the interface between the plates in a subduction zone?

2. Do the rocks on the subducting plate subduct as a relatively coherent sequence of lithosphere?
Photos courtesy of Sarah Penniston-Dorland
Subduction-related rocks from some localities, e.g. the Alps are found in large part as large sheets of oceanic lithosphere that are fault-bounded.

3. Do the rocks at the interface become sheared and mixed together?
Photos courtesy of Sarah Penniston-Dorland
Block
Mélange Matrix
Mélange
Mélange Matrix
Block
Block
Mélange Matrix
Subduction-related rocks from other localities, e.g. California are found as jumbled mafic, ultramafic, and sedimentary blocks that are surrounded by fine-grained matrix in mélange zones.

4. Endmember behaviors of rocks within subduction zone
Coherent
Melange
(Redrawn after Bebout, 2007)

5. Resources
Bebout, G.E., 2007, Metamorphic chemical geodynamics of subduction zones, Earth and Planetary Science Letters, 260,