This document provides an overview of transform plate boundaries, including: 1. Transform boundaries are zones where plates slide horizontally past each other with strong deformation but no new lithosphere is created or consumed. 2. There are three types of transform boundaries: ridge-ridge, ridge-trench, and trench-trench. Oceanic transforms form long fracture zones perpendicular to mid-ocean ridges. 3. Examples of prominent ocean fracture zones include the Romanche Fracture Zone and Clipperton Fracture Zone. Continental transforms like the San Andreas Fault accommodate plate motions but have more complex structures.

1. Transform plate boundary
By
Abd Al Rahman Ibrahim Soliman,
BSc of Geoscience,
Faculty of science, Alexandria University.
abdalrahmanibrahim209@gmail.com

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Agenda
Transform plate boundary
Introduction
 Characteristics of transform plate boundaries
 Types of Transform Plate Boundaries
o Ridge-ridge transform faults
o Ridge-trench transforms
o Trench-trench transforms
 Oceanic transform plate boundaries and fracture zones
o Examples of Oceanic Fracture Zones
 Romanche Fracture Zone
 Clipperton Fracture Zone
 Transform Fault Zones in Ophiolites
 Processes at transform plate boundaries
o Contraction and Extension in Transform Fault Systems.
o Thermal Structure and the “Cold Wall.”
o Ridge Offset and Spreading Rate
 Continental transform faults
o Examples of Continental Transform Faults
 San Andreas–Gulf of California Transform System
 Dead Sea Transform System.
 Alpine Transform System of New Zealand.
 Earthquakes at transform boundaries

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Introduction
Transform plate boundary

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Introduction
Transform plate boundary
Transform plate boundaries are zones of
shearing, where two plates slide
horizontally past each other. Rocks in the
shear zone are strongly deformed, but no
new lithosphere is created and none is
consumed. Transform boundaries in
ocean basins and on the continents are
expressed by steep, linear ridges and

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Introduction
Transform plate boundary
Transform plate boundaries are zones of
shearing, where two plates slide
horizontally past each other. Rocks in the
shear zone are strongly deformed, but no
new lithosphere is created and none is
consumed. Transform boundaries in
ocean basins and on the continents are
expressed by steep, linear ridges and

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Agenda
Transform plate boundary
 Types of Transform Plate Boundaries
o Ridge-ridge transform faults
o Ridge-trench transforms
o Trench-trench transforms
 Oceanic transform plate boundaries and fracture zones
o Examples of Oceanic Fracture Zones
 Romanche Fracture Zone
 Clipperton Fracture Zone
 Transform Fault Zones in Ophiolites
 Processes at transform plate boundaries
o Contraction and Extension in Transform Fault Systems.
o Thermal Structure and the “Cold Wall.”
o Ridge Offset and Spreading Rate
 Continental transform faults
o Examples of Continental Transform Faults
 San Andreas–Gulf of California Transform System
 Dead Sea Transform System.
 Alpine Transform System of New Zealand.
 Earthquakes at transform boundaries

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Types of Transform Plate Boundaries
Transform plate boundary
1. Ridge-ridge transform faults….Most
abundant

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map of the major transform plate boundaries and associated oceanic fracture zones
Transform plate boundary

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map of the major transform plate boundaries and associated oceanic fracture zones
Transform plate boundary

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Types of Transform Plate Boundaries
Transform plate boundary
2. Ridge-trench transforms….less common

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map of the major transform plate boundaries and associated oceanic fracture zones
Transform plate boundary

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map of the major transform plate boundaries and associated oceanic fracture zones
Transform plate boundary

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Types of Transform Plate Boundaries
Transform plate boundary
3. Trench-trench transforms …. Rare

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map of the major transform plate boundaries and associated oceanic fracture zones
Transform plate boundary

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map of the major transform plate boundaries and associated oceanic fracture zones
Transform plate boundary

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Agenda
Transform plate boundary
 Oceanic transform plate boundaries and fracture zones
o Examples of Oceanic Fracture Zones
 Romanche Fracture Zone
 Clipperton Fracture Zone
 Transform Fault Zones in Ophiolites
 Processes at transform plate boundaries
o Contraction and Extension in Transform Fault Systems.
o Thermal Structure and the “Cold Wall.”
o Ridge Offset and Spreading Rate
 Continental transform faults
o Examples of Continental Transform Faults
 San Andreas–Gulf of California Transform System
 Dead Sea Transform System.
 Alpine Transform System of New Zealand.
 Earthquakes at transform boundaries

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Oceanic transform plate boundaries and fracture zones
Transform plate boundary
Transform plate boundaries in the ocean
basins are prominent linear features that
are perpendicular to the midocean ridges.
They are the short, active parts of fracture
zones that may be several kilometers wide
and thousands of kilometers long.

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Oceanic transform plate boundaries and fracture zones
Transform plate boundary
Transform plate boundaries in the ocean
basins are prominent linear features that
are perpendicular to the midocean ridges.
They are the short, active parts of fracture
zones that may be several kilometers wide
and thousands of kilometers long.

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Oceanic transform plate boundaries and fracture zones
Transform plate boundary

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hallmarks of oceanic transform fault
Transform plate boundary
Intense shearing occurs at transform plate boundaries. This map of
the flanks of the mid-Atlantic ridge shows all of the hallmarks of a
transform fault. Linear valleys, depressions, and ridges are all aligned
along the fault.

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Oceanic transform plate boundaries and fracture zones
Transform plate boundary
Oceanic transform plate boundaries are part
of even longer features called fracture zones
Fracture zones are enormous structures that
range up to 10,000 km long and may have a
vertical relief of 6 km.

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Agenda
Transform plate boundary
o Examples of Oceanic Fracture Zones
 Romanche Fracture Zone
 Clipperton Fracture Zone
 Transform Fault Zones in Ophiolites
 Processes at transform plate boundaries
o Contraction and Extension in Transform Fault Systems.
o Thermal Structure and the “Cold Wall.”
o Ridge Offset and Spreading Rate
 Continental transform faults
o Examples of Continental Transform Faults
 San Andreas–Gulf of California Transform System
 Dead Sea Transform System.
 Alpine Transform System of New Zealand.
 Earthquakes at transform boundaries

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Romanche Fracture Zone
Transform plate boundary
• The most spectacular fracture in the
central Atlantic Ocean is the Romanche
fracture system, which lies almost on the
equator
• ridge-ridge transform fault between the
African plate on the north and the South
American plate on the south.

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Romanche Fracture Zone
Transform plate boundary

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Romanche Fracture Zone
Transform plate boundary
•
• ridge-ridge transform fault between the
African plate on the north and the South
American plate on the south.

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Romanche Fracture Zone
Transform plate boundary
•
• ridge-ridge transform fault between the
African plate on the north and the South
American plate on the south.

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Romanche Fracture Zone ……. closer look
Transform plate boundary

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Romanche Fracture Zone ……. closer look
Transform plate boundary
• The Romanche fracture zone extends
across most of the Atlantic Ocean, forming
a huge ridge and trough system some
5000 km long and almost 100 km wide.
The active transform boundary lies
between the offset ridge axis.

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Clipperton Fracture Zone
Transform plate boundary
The Clipperton fracture zone stretches from
the coast of Central America to the middle of
the Pacific Ocean

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Clipperton Fracture Zone
Transform plate boundary

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Clipperton Fracture Zone
Transform plate boundary
The Clipperton transform fault cuts the East Pacific Rise,
in the northern part of this map. It is just west of the Centr
al American coast. The transform fault forms a series of ri
dges and troughs connecting two segments of the oceani
c ridge. The offset is about 85 km.

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Clipperton Fracture Zone
Transform plate boundary

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Transform Fault Zones in Ophiolites
Transform plate boundary
The Troodos ophiolite complex on the Mediterranean island of Cyprus is
cut by such a vertical shear zone The shear zone is about 10 km wide and
cuts through the rocks of the ophiolite sequence. Dikes in a sheeted dike
complex curve toward the major strike-slip fault, just as ridge tips do a
transform fault zone. Outcrops of gabbro and serpentinite lie on the
south side of the fault. The large mass of serpentine is interpreted to have
formed when peridotite in the mantle combined with seawater flowing
through the highly permeable fracture zone. Because serpentine is both
buoyant and weak, it may have intruded into the fracture zone as a
diapir. Talus breccias formed as steep slopes on the seafloor failed.
Apparently, high ridges and deep valleys ran parallel to the shear zone.
The breccias are interlayered with sediments and basaltic lava flows,
which include pillow basalts. Small volumes of lava must have erupted
along the shear zone. All of these features reveal that this area of the
ophiolite was strongly sheared along a strike-slip fault while it was still at the

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Transform Fault Zones in Ophiolites
Transform plate boundary

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Agenda
Transform plate boundary
 Processes at transform plate boundaries
o Contraction and Extension in Transform Fault Systems.
o Thermal Structure and the “Cold Wall.”
o Ridge Offset and Spreading Rate
 Continental transform faults
o Examples of Continental Transform Faults
 San Andreas–Gulf of California Transform System
 Dead Sea Transform System.
 Alpine Transform System of New Zealand.
 Earthquakes at transform boundaries

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Contraction and Extension in Transform Fault Systems
Contraction and Extension in Transform Fault Systems

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Processes at transform plate boundaries …….Transpression
Contraction and Extension in Transform Fault Systems
Horizontal compression occurs where the bends
are oriented so that blocks on either side of
the fault are squeezed together This squeezing
creates uplifted regions with small folds and thrust
faults that trend perpendicular to the major strike
slip faults. Because this process involves both
transform and compression motion, it is known as
transpression. This kind of contraction commonly
creates long, low ridges, but locally, uplift may
be extreme.

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Processes at transform plate boundaries …….Transpression
Contraction and Extension in Transform Fault Systems

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Processes at transform plate boundaries …….Transtension
Contraction and Extension in Transform Fault Systems
Areas of extension can also develop along bends
in the strike-slip faults. Transtension (transform
plus extension) produces small fault-bounded
troughs known as pull-apart basins

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Processes at transform plate boundaries …….Transtension
Contraction and Extension in Transform Fault Systems

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Processes at transform plate boundaries …….Transtension
Contraction and Extension in Transform Fault Systems

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Processes at transform plate boundaries
Contraction and Extension in Transform Fault Systems

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Flower structure
Contraction and Extension in Transform Fault Systems
• vertical movements are associated with normal
faults, reverse faults or folds. Acharacteristic
feature of such bends is their tendency to split
and widen upward, These structures are called
flower structures
• Flower structures that are associated with
restraining bends are called positive, and those
associated with releasing bends are called
negative flower structures.

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Flower structure
Contraction and Extension in Transform Fault Systems
Flower structures that are associated with
restraining bends are called positive, and those
associated with releasing bends are called
negative flower structures.

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Positive flower structure
Contraction and Extension in Transform Fault Systems

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Negative Flower structure
Contraction and Extension in Transform Fault Systems

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Agenda
Transform plate boundary
 Continental transform faults
o Examples of Continental Transform Faults
 San Andreas–Gulf of California Transform System
 Dead Sea Transform System.
 Alpine Transform System of New Zealand.
 Earthquakes at transform boundaries

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Continental transform faults:
Transform plate boundary
• Transform faults that cut continental crust are not
nearly as common as oceanic transforms because
most transform faults develop at oceanic ridges.
• Continental transform faults typically have distinctive
linear topographic features These include relatively
straight fault scarps, linear ridges and troughs, and
streams and valleys that have been beheaded and
displaced horizontally. The individual faults in a
continental transform system therefore branch, join,
bend, and sidestep each other and even establish
zones of local contraction or extension.

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The San Andreas Fault
Transform plate boundary
• The San Andreas Gulf of California transform
system is 3000 km long, extending from
the Mendocino fracture zone off the northern
coast of California southward to the tip of
Baja California .

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The San Andreas Fault
Transform plate boundary

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Clipperton Fracture Zone
Transform plate boundary

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The San Andreas Fault
Transform plate boundary
• The San Andreas Fault itself is more than 1000
km long, an active boundary between the
Pacific plate to the west and the North
American plate to the east. The Pacific plate is
moving northwestward at about 6 cm/yr. relative
to the North American plate. As stress builds
between the plates, sudden releases cause the
earthquakes for which California is noted.
Earthquakes occur along its entire length and
as deep as 15 km, but no deeper.

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The San Andreas Fault
Transform plate boundary
• The San Andreas Fault system began to
develop about 30 million years ago (in
Oligocene time) and its location on the
continent may have been controlled by
preexisting fractures in the basement rocks.
Horizontal movement along the San Andreas
Fault has totaled about 300 km.

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The San Andreas Fault
Transform plate boundary
• The net result of movement along the San
Andreas Gulf of California transform system
has been the opening of the Gulf of California
and the displacement of the western block of
the San Andreas northward approximately 300
km With continued movement, Baja
California and a narrow slice of western
California may become an elongate continental
fragment surrounded by oceanic crust.

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San Andreas Fault
Transform plate boundary

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Dead sea
Transform plate boundary
• The Dead Sea transform system extends from
the spreading ridge of the Red Sea northward
to a zone of continent-to-continent collision in
the Alpine orogenic belt in southern Turkey

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Dead sea
Transform plate boundary

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Dead sea
Transform plate boundary
• The structure, topography, and history of
the entire region are magnificent
expressions of continental plates moving
along a transform system. The transform
zone is about 1000 km long and marks the
boundary between the western edge of the
Arabian plate and the northern part of the
African plate.

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Agenda
Transform plate boundary
.
 Earthquakes at transform boundaries

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Earthquakes and magmatism at transform boundaries
Transform plate boundary