Geology
Structure: An Introduction to Deformation
Name_____________
Standards

Describe the composition and structure of Earth’s materials

Describe the internal structure of Earth and the structure of Earth’s plates
I. A Brief Intro to Mapping
A. Geologic ___________ – represent the rock ___________________ exposed at
Earth’s surface.
1. Maps have special symbols to indicate strike and dip of rock formations, and
lines to mark faults
B. Strike and Dip
1. ___________ – the compass ________________ of a rock layer as it intersects
with a horizontal surface
2. ________ – is measured at right angles to strike and is the amount of
_______________ of the formation (angle at which the bed is inclined for the
horizontal)
C. Geologic ___________ Sections
1. Diagrams that show the features that would be visible if vertical slices were
made through part of the crust
2. Shows the rocks and structures ______________ the surface
II. Plate Tectonics
A. Steady motion between plates causes _____________________at plate boundaries.
1. Rocks are deformed by ________________ and ________________.
a. Layers of rock can be pushed into folds.
b. Or, rock formations can break and slip on both sides of a fracture,
forming a fault.
B. Review Types of Plate Boundaries
1. Convergent - Plates ___________ together
2. Divergent - Plates ____________ apart
3. Transform - Plates slide ____________________ past each other
C. Types of Plate Tectonic Force
1. __________________ forces – stretch and _________ formations apart.
• Dominate at divergent boundaries.
2. _____________________ forces – ________________ and shorten rock
formations.
• Dominate at convergent boundaries.
3. _______________ forces – push two sides of a formation in opposite directions.
• Dominate at transform boundaries.
1
III. Ductile vs. Brittle
A. ________________ material – a material that undergoes little deformation under
increasing force until it suddenly _______________
B. _______________ material – a material that undergoes smooth and continuous
________________ deformation under increasing force and does not spring back to
its original shape when the force is removed.
C. Brittle & Ductile Behavior in the Crust
1. Some rocks are brittle and others ductile.
2. The same rock can be ____________ at ____________ depths and
______________ ___________ in the crust
3. A rock formation that would flow as a ______________ material if deformed
_______________ may break as a _________________ material if deformed
more _______________.
• Exs: silly putty and gak
4. Rocks break more easily under tension than compression
IV. Basic Deformation Structures
-Faults
-Folds
-Circular Structures
-Joints
V. ____________
A. Surface across which rock __________________ have been ____________________
B. Offset can be centimeters to hundreds of kilometers
C. Faults are classified by their __________ direction:
1. Dip-slip fault
2. Strike-slip fault
D. _________-____________ Fault
1. There has been relative _____________________ of the blocks (rock to either
side of the fault) _____ or __________ the dip of the fault plane.
2. Dip = tilt of the fault
3. Caused by ___________________ or _________________ forces.
4. 3 types:
a. Normal fault
b. Reverse fault
c. Thrust fault
E. Fault Parts
1. ___________ – __________ along which rocks have been displaced
2. ______________ wall – rocks ____________ fault plane
3. __________ wall – rocks ____________ fault plane
Draw and label diagram in space below:
2
F. _____________ Fault
1. Dip-slip fault formed when rocks above the fault plane (on the top side of the
dip) move ______________ relative to rocks below the fault plane.
2. This ______________ the structure horizontally.
3. Formed by __________________ forces
G. ________________ Fault
1. Rocks above fault plane move _______________ in relation to the rocks below.
2. Causes __________________ of the structure.
3. Formed by ___________________ forces
H. _______________ Fault
1. _________-_____________ reverse fault – the angle of the fault plane is less
than ____°
2. This causes the overlying block to move _________________
I. _______________ Slip Fault
1. Movement is _________________ (just like movement at transform boundaries)
2. Caused by __________________ forces
3. Two types:
a. Right-lateral fault
b. Left-lateral fault
J. ___________-_____________ Fault
1. An observer on one side of the fault sees the block on the opposite side move to the
right.
K ___________-_____________ Fault
2. The block on the opposite side of the fault moves to the left.
L. Recognizing Faults in the Field
1. Faults may form a small cliff called a __________
2. Formations that have large offsets (like on the San Andreas) differ in age and
rock type
4. Small amounts of offset can be observed and measured
VI. ___________
A. A ____________ in rocks
B. Are often observed in __________________ rocks
C. Have a range of sizes
D. Two types:
1.Anticlines
2.Synclines
E. _______________
1. Layered rocks that fold ______________ into arches
2. _____________ rocks are in center of fold
F. _______________
1. Layered rocks that fold ________________ into troughs.
2. __________________ rocks are in center of fold
3. Synclines look like Smiles
3
G. Parts of Folds
1. Anticlines and synclines have limbs and an axial plane:
a. ______________ – the two ___________ of the fold
b. ______________ plane – an imaginary surface that divides a fold as
symmetrically as possible, with one limb on either side of the plane
H. _____________________ Fold
1. Forms when deformation is intense and one limb has been tilted beyond the
vertical.
2. Both limbs dip in the same direction, but the ___________ of _____________ in
the bottom limb is the ______________ of their original sequence – that is,
older rocks are on top of younger rocks
VII. ________________ Structures
A. In many cases, these form from upward force of rising material or downward
force of sinking material
B. Two types:
1.Dome
2.Basin
C. _____________
1. Broad, circular or oval upward bulge of rock layers
2. Type of anticline
D. _____________
1. Bowl-shaped depression of rock layers
2. Type of syncline
VIII. _____________
A. A type of ________________, or crack, along which there has been no movement.
B. Found in almost every outcrop
C. Formed by:
1. Tectonic forces
2. _________________ & __________________ of rocks
IX. Deformation __________________
A. As rocks along a fault plane move past each other, they grind and fragment
B. ______________ deformation will form fault ________________
C. ______________ deformation deeper in the crust will form _________________
D. Fault Breccias
1. Rocks with a ____________ appearance
E. Mylonites
1. Minerals __________________ and ____________ out in bands or streaks.

L. Brown
Updated April 2014
4