Matthiessen, J., Mildenhal, D. C., Mudie, P., Neil, H. L.,
Pospelova, V., Qi, Y., Radi, T., Richerol, T., Rochon, A.,
Sangiorgi, F., Solignac, S., Turon, J.-L., Verleye, T., Wang, Y.,
Wang, Z., and Young, M., 2013. Atlas of modern dinoflagellate
cyst distribution based on 2405 data points. Review of
Palaeobotany and Palynology, 191, 1–197.
Cross-references
Deep-sea Sediments
Marine Microfossils
Paleoceanography
Paleoceanographic Proxies
DRIVING FORCES: SLAB PULL, RIDGE PUSH
Carolina Lithgow-Bertelloni
Department of Earth Sciences, University College
London, London, UK
Definition
Plate Driving Forces: The forces that drive the motions of
tectonic plates at the surface.
Slab Pull: The force exerted by the weight of the
subducted slab on the plate it is attached to.
Ridge Push: The pressure exerted by the excess height
of the mid-ocean ridge.
Introduction
The history of the development of plate tectonics is centrally tied to the question of what drives plate motions.
This has been the case since the failure of Wegener’s ideas
about polflucht to explain continental drift to the seminal
papers by Elsasser (1969), Solomon and Sleep (1974),
and Forsyth and Uyeda (1975) on slab pull and ridge push.
This contribution cannot possibly review all the seminal
and historical publications that led to the establishment
of the terms and concepts of slab pull and ridge push as
major plate driving forces; instead, it gives a brief historical introduction and then focuses on modern views of the
plate-mantle system and what remains to be understood.
Historical overview
Beginning studies on plate driving forces all used parameterizations of forces acting at plate boundaries (e.g.,
Solomon and Sleep, 1974; Harper, 1975; Forsyth and
Uyeda, 1975; Chapple and Tullis, 1977). This choice
was partly out of necessity and partly a historical remnant
of the development of plate tectonics with a contraposition
of surface and interior. The perspective necessarily was a
geological one, focusing on what could be seen and
observed. Seminal early work focused on mantle convection and showed that the top thermal boundary layer of the
convecting system could have plate-like properties and
velocities (Turcotte and Oxburgh, 1967). This division
between studies of plate driving forces from the plate or
mantle perspective remains today. Early studies were
partly influenced by the need to explain the apparent contradiction between a fluid, weak mantle, and transmitting
stresses to strong plates, a corollary to Harold Jeffreys’
objections to continental drift. These were the days before
global seismic tomography (Dziewonski et al., 1977) and
there was an understandable reluctance to correlate deep
and unseen mantle structure with the surface. The existence of a low-velocity zone (the asthenosphere), which
coincided (Anderson, 2007) with a very weak, very
low-viscosity region, furthered the notion that stresses
from mantle convection could not be transmitted to the
lithosphere and effectively decoupled plates from the
mantle. All return flow generated by the subduction of
slabs was limited to convection in the asthenosphere
(Forsyth and Uyeda, 1975). As global tomographic
models emerged (Dziewonski et al., 1977), the suggestion
that global geoid anomalies were correlated with past subduction (Chase and Sprowl, 1983) opened the door for
studies that linked interior flow and surface motions.
These ideas culminated in the classic papers of Hager
and O’Connell (1981) on plate motions and driving forces
in the context of mantle flow. The clear correlation
between the long-wavelength pattern of subduction, mantle flow, and the geoid (Richards and Engebretson, 1992)
further motivated the link between convection and the
interior, leading to integrated studies of mantle flow to
predict plate motions incorporating ever larger complexity
in rheology and boundary conditions (Ricard and Vigny,
1989; Lithgow-Bertelloni and Richards, 1995; Becker
and O’Connell, 2001; Conrad and Lithgow-Bertelloni,
2002; Becker, 2006; Stadler et al., 2010; van Summeren
et al., 2012).
Basic principles
Plate driving forces in the traditional formulation are driving and resisting forces acting at the edges and the base of
lithospheric plates, balanced so that there is no-net torque
on any given plate or the lithosphere as a whole (Solomon
and Sleep, 1974). In other words, plates are in dynamical
equilibrium. The assumption of no-net torque is justified
by the high viscosity of mantle and lithosphere, precluding
acceleration and inertial forces. The balance of forces is
best illustrated in the formulation of Forsyth and Uyeda
(1975) shown in Figure 1. The main driving forces are slab
pull (F SP ) and ridge push (F RP ), and forces like mantle
drag (F DF and F CD ) can both oppose and drive plate
motions. Suction (F SU ), first identified by Elsasser
(1971), pulls the overriding plate toward the trench. There
are significant resisting forces, slab resistance (F SR ), transform resistance (F TF ), and collisional resistance (F CR ). For
the sake of brevity, we only focus on slab pull and ridge
push.
Slab pull is defined as F SP ¼ DrgsinyV s where Dr is
the density contrast between the slab and the surrounding
mantle, g the gravitational acceleration, y is the dip angle
of the slab, and V S the volume of the slab. The slab pulls
DRIVING FORCES: SLAB PULL, RIDGE PUSH
193
Pospelova, V., Qi, Y., Radi, T., Richerol, T., Rochon, A.,
Sangiorgi, F., Solignac, S., Turon, J.-L., Verleye, T., Wang, Y.,
Wang, Z., and Young, M., 2013. Atlas of modern dinoflagellate
cyst distribution based on 2405 data points. Review of
Palaeobotany and Palynology, 191, 1–197.
Cross-references
Deep-sea Sediments
Marine Microfossils
Paleoceanography
Paleoceanographic Proxies
DRIVING FORCES: SLAB PULL, RIDGE PUSH
Carolina Lithgow-Bertelloni
Department of Earth Sciences, University College
London, London, UK
Definition
Plate Driving Forces: The forces that drive the motions of
tectonic plates at the surface.
Slab Pull: The force exerted by the weight of the
subducted slab on the plate it is attached to.
Ridge Push: The pressure exerted by the excess height
of the mid-ocean ridge.
Introduction
The history of the development of plate tectonics is centrally tied to the question of what drives plate motions.
This has been the case since the failure of Wegener’s ideas
about polflucht to explain continental drift to the seminal
papers by Elsasser (1969), Solomon and Sleep (1974),
and Forsyth and Uyeda (1975) on slab pull and ridge push.
This contribution cannot possibly review all the seminal
and historical publications that led to the establishment
of the terms and concepts of slab pull and ridge push as
major plate driving forces; instead, it gives a brief historical introduction and then focuses on modern views of the
plate-mantle system and what remains to be understood.
Historical overview
Beginning studies on plate driving forces all used parameterizations of forces acting at plate boundaries (e.g.,
Solomon and Sleep, 1974; Harper, 1975; Forsyth and
Uyeda, 1975; Chapple and Tullis, 1977). This choice
was partly out of necessity and partly a historical remnant
of the development of plate tectonics with a contraposition
of surface and interior. The perspective necessarily was a
geological one, focusing on what could be seen and
observed. Seminal early work focused on mantle convection and showed that the top thermal boundary layer of the
convecting system could have plate-like properties and
velocities (Turcotte and Oxburgh, 1967). This division
between studies of plate driving forces from the plate or
mantle perspective remains today. Early studies were
partly influenced by the need to explain the apparent contradiction between a fluid, weak mantle, and transmitting
stresses to strong plates, a corollary to Harold Jeffreys’
objections to continental drift. These were the days before
global seismic tomography (Dziewonski et al., 1977) and
there was an understandable reluctance to correlate deep
and unseen mantle structure with the surface. The existence of a low-velocity zone (the asthenosphere), which
coincided (Anderson, 2007) with a very weak, very
low-viscosity region, furthered the notion that stresses
from mantle convection could not be transmitted to the
lithosphere and effectively decoupled plates from the
mantle. All return flow generated by the subduction of
slabs was limited to convection in the asthenosphere
(Forsyth and Uyeda, 1975). As global tomographic
models emerged (Dziewonski et al., 1977), the suggestion
that global geoid anomalies were correlated with past subduction (Chase and Sprowl, 1983) opened the door for
studies that linked interior flow and surface motions.
These ideas culminated in the classic papers of Hager
and O’Connell (1981) on plate motions and driving forces
in the context of mantle flow. The clear correlation
between the long-wavelength pattern of subduction, mantle flow, and the geoid (Richards and Engebretson, 1992)
further motivated the link between convection and the
interior, leading to integrated studies of mantle flow to
predict plate motions incorporating ever larger complexity
in rheology and boundary conditions (Ricard and Vigny,
1989; Lithgow-Bertelloni and Richards, 1995; Becker
and O’Connell, 2001; Conrad and Lithgow-Bertelloni,
2002; Becker, 2006; Stadler et al., 2010; van Summeren
et al., 2012).
Basic principles
Plate driving forces in the traditional formulation are driving and resisting forces acting at the edges and the base of
lithospheric plates, balanced so that there is no-net torque
on any given plate or the lithosphere as a whole (Solomon
and Sleep, 1974). In other words, plates are in dynamical
equilibrium. The assumption of no-net torque is justified
by the high viscosity of mantle and lithosphere, precluding
acceleration and inertial forces. The balance of forces is
best illustrated in the formulation of Forsyth and Uyeda
(1975) shown in Figure 1. The main driving forces are slab
pull (F SP ) and ridge push (F RP ), and forces like mantle
drag (F DF and F CD ) can both oppose and drive plate
motions. Suction (F SU ), first identified by Elsasser
(1971), pulls the overriding plate toward the trench. There
are significant resisting forces, slab resistance (F SR ), transform resistance (F TF ), and collisional resistance (F CR ). For
the sake of brevity, we only focus on slab pull and ridge
push.
Slab pull is defined as F SP ¼ DrgsinyV s where Dr is
the density contrast between the slab and the surrounding
mantle, g the gravitational acceleration, y is the dip angle
of the slab, and V S the volume of the slab. The slab pulls
DRIVING FORCES: SLAB PULL, RIDGE PUSH
193