MORPHOLOGY ACROSS CONVERGENT PLATE
BOUNDARIES
Wolfgang Frisch
Department of Geosciences, University of Tübingen,
Tübingen, Germany
Definition
Convergent plate boundaries are plate boundaries where
one plate subducts beneath the other due to convergent
plate movement. Due to its higher density, mostly oceanic
lithosphere is the subducting part.
Four types of convergent plate boundaries
Four types of convergent plate boundaries are recognized
(Figures 1 and 2):
The first type occurs when oceanic lithosphere is
subducted below another oceanic lithosphere
(“Intraoceanic Subduction Zone”) to create a volcanic
island arc system built on oceanic crust (“ensimatic island
arc”; sima – artificial word first used by Wegener made
from silicon and magnesium to characterize ocean floor
and Earth’s mantle). Examples for intraoceanic, ensimatic
island arc systems include the Mariana Islands in the
Pacific and the Lesser Antilles in the Atlantic.
The second type occurs where oceanic lithosphere is
subducted beneath continental lithosphere and an island arc
underlain by continental crust forms (“ensialic island arc”;
sial – silicon and aluminum for continental crust). The island
arc of this system is separated from the continent by a marine
basin underlain by oceanic crust. Examples for island arc
systems underlain by continental crust are the Japanese
Islands and the eastern Sunda Arc.
The third type of convergent plate boundary represents
the active continental margins where oceanic lithosphere
is subducted beneath continental lithosphere without
a marine basin behind the volcanic arc; rather, the arc is
built directly on the adjacent continent. The continental
margin is connected directly to the hinterland, although
a shallow marine basin may exist behind the volcanic
arc. Examples for active continental margins are the
Andes, SE Alaska, and the western and central Sunda
Arc that includes Sumatra and Java.
The fourth type of convergent margin occurs along
zones of continent-continent collision. If two continental
Morphology Across Convergent Plate Boundaries, Figure 1 Convergent plate margins of the Earth characterized by ensimatic
island arcs (underlain by oceanic crust), ensialic island arcs (underlain by continental crust), and active continental margins.
MORPHOLOGY ACROSS CONVERGENT PLATE BOUNDARIES
523
BOUNDARIES
Wolfgang Frisch
Department of Geosciences, University of Tübingen,
Tübingen, Germany
Definition
Convergent plate boundaries are plate boundaries where
one plate subducts beneath the other due to convergent
plate movement. Due to its higher density, mostly oceanic
lithosphere is the subducting part.
Four types of convergent plate boundaries
Four types of convergent plate boundaries are recognized
(Figures 1 and 2):
The first type occurs when oceanic lithosphere is
subducted below another oceanic lithosphere
(“Intraoceanic Subduction Zone”) to create a volcanic
island arc system built on oceanic crust (“ensimatic island
arc”; sima – artificial word first used by Wegener made
from silicon and magnesium to characterize ocean floor
and Earth’s mantle). Examples for intraoceanic, ensimatic
island arc systems include the Mariana Islands in the
Pacific and the Lesser Antilles in the Atlantic.
The second type occurs where oceanic lithosphere is
subducted beneath continental lithosphere and an island arc
underlain by continental crust forms (“ensialic island arc”;
sial – silicon and aluminum for continental crust). The island
arc of this system is separated from the continent by a marine
basin underlain by oceanic crust. Examples for island arc
systems underlain by continental crust are the Japanese
Islands and the eastern Sunda Arc.
The third type of convergent plate boundary represents
the active continental margins where oceanic lithosphere
is subducted beneath continental lithosphere without
a marine basin behind the volcanic arc; rather, the arc is
built directly on the adjacent continent. The continental
margin is connected directly to the hinterland, although
a shallow marine basin may exist behind the volcanic
arc. Examples for active continental margins are the
Andes, SE Alaska, and the western and central Sunda
Arc that includes Sumatra and Java.
The fourth type of convergent margin occurs along
zones of continent-continent collision. If two continental
Morphology Across Convergent Plate Boundaries, Figure 1 Convergent plate margins of the Earth characterized by ensimatic
island arcs (underlain by oceanic crust), ensialic island arcs (underlain by continental crust), and active continental margins.
MORPHOLOGY ACROSS CONVERGENT PLATE BOUNDARIES
523