Download Unit 1 Lesson 3: Definition Assignment (Original)

Unit 1 Lesson 3: Definition Assignment (Original)
Introduction: In this week’s assignment, unit 1:3, I was assigned an assignment to create three
definitions: a parenthetical definition, a sentence definition, and an expanded definition for a
complex term within my discipline. From this, I was able to explore many expanding strategies
when writing an expanded definition.
Chosen term: Listric normal fault
Situation: Explaining what a listric normal fault is to my retired neighbor.
Parenthetical Definition:
A listric normal fault (curved fault) is present in any type of environment where two plates are
separating.
Sentence Definition:
Listric normal fault is a type of fault resulting from tectonic separation, where an upper fault
block, known as the hanging wall, descends along a curved fault surface.
Expanded Definition:
Where is a “listric normal fault”?
Listric normal fault is a type of fault resulting from tectonic separation, where an upper fault
block, known as the hanging wall, descends along a curved fault surface. A listric normal fault is
characterized by a decrease in dip angle along the fault with depth.
Where is it found?
Listric normal faults have long been associated with extensional regimes. They are
characterized by a clear curvature with depth. It is common in spreading ridges, continental
rifts, and can be affected by gravity-related tectonism (Maloney et al. 109). Since faults rarely
form alone, a listric normal fault would be common in these regions as they utilize the same
stress as an extensional environment.
What constitutes this fault?
The following key elements define a listric normal fault:

A curved master detachment fault, which allows the displacement of fault blocks

A deformed hanging wall fault block, which lies above the curved fault
A fixed footwall fault block, which lies under the curved fault
Rollover within the hanging wall due to its downward motion along a curved surface and
deformation



A fault angle less than thirty degrees
As the hanging wall descends down the curved fault, the rock becomes unstable and collapses;
forming a rollover effect or an antithetic (younger faults in the opposite direction of the main
fault) feature during deformation (Williams 789).
How does it occur?
Listric normal faults are formed when two plates break apart in a divergent manner. This
induces shear stress on the master detachment fault. During fault movement, the hanging wall
above the curved detachment fault descends and undergoes deformation to fill in empty
spaces along the fault surface. However, the footwall, the fault block beneath the fault, remains
fixed. The curvature of the detachment fault causes the hanging wall to rotate and form a
rollover structure as it accommodates movement along a curved surface. The displacement
along the fault is controlled by lithology (rock characteristics), pore pressure (pressure applied
to water), or slope failure. Fluids, such as water, help to reduce friction within the fault, making
sliding easier for the fault blocks (Maloney et al. 107-109).
How is it distinguished from a normal fault?
A normal planar fault is similar to a listric normal fault in the way the hanging wall moves.
However, the two faults are controlled by different processes. A listric normal fault focuses
primarily on the deformation of the hanging wall along a curved fault surface. A normal planar
faults’ surface is planar-not curvy.
Works Cited:
Maloney, D., et al. “Structure of the footwall of a listric fault system revealed by 3D seismic data
from the Niger Delta.” Basin Research 24 (2012): 107-123. Web 15 Sept. 2014
Parenthetical Reference: (Maloney et al. 107-109)
Spahic, D., et al. “Listric versus planar normal fault geometry: an example from the EisenstadtSopron Basin (E Austria).” Springer-Verlag 100 (2011): 1685-1695. Web 15 Sept. 2014
Parenthetical reference: (Spahic et al. 1685-1692)
Williams, G. “The geometry of listric normal faults and deformation in their hanging walls.”
Journal of Structural Geology 7 (1987): 789-795. Web 15 Sept. 2014
Parenthetical reference: (Williams 789)
Unit 1 Lesson 3: Definition Assignment (Edited)
Introduction: In this week’s assignment, unit 1:3, I was assigned an assignment to create three
definitions: a parenthetical definition, a sentence definition, and an expanded definition for a
complex term within my discipline. From this, I was able to explore many expanding strategies
when writing an expanded definition.
Chosen term: Listric normal fault
Situation: Explaining what a listric normal fault is to my retired neighbor.
Parenthetical Definition:
A listric normal fault (curved fault) is present in any type of environment where two tectonic plates
are separating.
Sentence Definition:
Listric normal fault is a type of fault resulting from tectonic separation, where an upper fault block,
known as the hanging wall, descends along a curved fault surface.
Expanded Definition:
What is a listric normal fault?
Listric normal fault is a type of fracture in the earth resulting from tectonic activity, where a piece of
the earth’s crust slides down a curved surface due to the plates pulling apart.
Where are listric normal faults found?
Listric normal faults are associated with the separation of tectonic plates. They are characterized by
a curved fault surface (a curved fracture in the earth’s crust caused by movement of the tectonic
plates) down which a piece of earth falls. Listric normal faults is common in places where the land is
separating (Maloney et al. 109).
What constitutes a listric normal fault?
The following key elements define a listric normal fault:

A main curved fracture known as a master detachment fault, which allows the displacement of
the rocks

A deformed piece of Earth (hanging wall fault block) that descends. It lies above the curved
fracture

A fixed piece of Earth (footwall fault block), which lies under the curved crack and remains
motionless

A fracture that has an angle less than thirty degrees from horizontal
As the hanging wall descends down the curved fracture, the rock becomes unstable and collapses;
forming a “rollover effect” (Williams 789).
How does a listric normal fault occur?
Listric normal faults are formed when two plates break apart and begin to move away from each
other. This induces stress on the main curved fracture. During fault (fracture in the Earth’s surface)
movement, the piece of rock above the curved fracture descends and deforms to fill in empty spaces
along the fracture’s surface. However, the footwall (piece of rock underlying the fracture) remains
fixed. The curvature of the fracture causes the piece of rock above it to rotate and form a rollover
structure. A rollover structure accommodates movement along a curved surface. The displacement
along the fracture is controlled by lithology (rock characteristics), pore pressure (pressure applied to
water), or slope failure. Fluids, such as water, help to reduce friction within the fracture, making
sliding easier for the hanging wall (Maloney et al. 107-109).
How is a listric normal fault distinguished from a normal fault?
A normal planar fault is similar to a listric normal fault in the way the pieces of rocks above the
fracture moves. However, the two faults are controlled by different processes. A listric normal fault
focuses primarily on the deformation of the hanging wall (piece of rock above the fracture) along a
curved fracture surface. A normal planar faults’ surface is planar-not curvy.
s
Works Cited:
Maloney, D., et al. “Structure of the footwall of a listric fault system revealed by 3D seismic data
from the Niger Delta.” Basin Research 24 (2012): 107-123. Web 15 Sept. 2014
Parenthetical Reference: (Maloney et al. 107-109)
Spahic, D., et al. “Listric versus planar normal fault geometry: an example from the EisenstadtSopron Basin (E Austria).” Springer-Verlag 100 (2011): 1685-1695. Web 15 Sept. 2014
Parenthetical reference: (Spahic et al. 1685-1692)
Williams, G. “The geometry of listric normal faults and deformation in their hanging walls.”
Journal of Structural Geology 7 (1987): 789-795. Web 15 Sept. 2014
Parenthetical reference: (Williams 789)