Which structure is formed by **compressional forces** in the Earth's crust?
Analysis & Theory
Folds form due to compressional stress causing rock layers to bend.
A **downward** fold in rock layers is called a:
Analysis & Theory
Synclines are downward-curved folds with youngest rocks in the center.
The **limb** of a fold refers to:
C
The sides or arms of a fold
Analysis & Theory
Limb is the sloping side of a fold on either side of the hinge.
An **anticline** is a fold in which:
A
The limbs dip away from the hinge
B
The limbs dip towards the hinge
C
Rock layers are vertical
D
Rocks are completely fractured
Analysis & Theory
In anticlines, limbs dip away from the hinge and oldest rocks are at the core.
In which fold are both limbs dipping in the same direction but at different angles?
Analysis & Theory
Asymmetrical folds have limbs dipping in the same direction but unequally.
Which term refers to a fold lying horizontally?
Analysis & Theory
A recumbent fold has a horizontal axial plane and nearly parallel limbs.
Which fold type has both limbs dipping at equal angles in opposite directions?
Analysis & Theory
Symmetrical folds have equal dip angles on both sides.
Which fault is caused by **tensional forces**?
Analysis & Theory
Normal faults form due to tension, where hanging wall moves down.
The **hanging wall** in a normal fault:
Analysis & Theory
In a normal fault, the hanging wall moves downward relative to the footwall.
Which fault results from **compressional stress**?
Analysis & Theory
Thrust faults are low-angle reverse faults formed by compression.
Which fault has **horizontal displacement**?
Analysis & Theory
Strike-slip faults show lateral motion with minimal vertical displacement.
A fault where **vertical and horizontal movements** both occur is called:
Analysis & Theory
Oblique-slip faults combine vertical and horizontal movement.
The **plane of fracture** in a fault is called:
Analysis & Theory
Fault plane is the surface along which displacement occurs.
The area **between two faults** that moves downward is called:
Analysis & Theory
A graben is a down-dropped block between two normal faults.
The **upthrown block** between two faults is called:
Analysis & Theory
Horsts are uplifted blocks between two faults.
Which structure is a **fracture with no displacement**?
Analysis & Theory
Joints are breaks in rocks without visible movement.
Joints are usually formed due to:
C
Stress release or cooling
Analysis & Theory
Joints form due to contraction, stress release, or thermal cooling.
A set of parallel joints is called a:
Analysis & Theory
A joint family is a group of parallel joints.
Which type of joints are formed due to **tensional stress**?
Analysis & Theory
Extension joints form due to tension, often vertical or horizontal.
Which of the following is **not** a type of joint?
Analysis & Theory
Graben is a fault structure, not a type of joint.
Unconformities represent a gap in the:
Analysis & Theory
Unconformities are surfaces representing missing time due to erosion or non-deposition.
An **angular unconformity** occurs when:
A
Older and younger beds are parallel
B
Younger rocks rest on eroded older tilted beds
C
Only igneous rocks are present
Analysis & Theory
Angular unconformities occur when younger strata overlie tilted or folded older strata.
A **nonconformity** separates:
B
Metamorphic/igneous and sedimentary layers
Analysis & Theory
A nonconformity is a boundary between crystalline basement rocks and overlying sediments.
A **disconformity** occurs between:
A
Igneous and sedimentary rocks
B
Two parallel sedimentary layers with erosion surface
C
Faulted and folded beds
D
Metamorphic and igneous rocks
Analysis & Theory
Disconformities are subtle gaps between parallel sedimentary layers with an erosional surface.
Which type of unconformity is most difficult to recognize?
Analysis & Theory
Disconformities often lack visible structural differences, making them hard to detect.
Which feature helps in identifying an angular unconformity?
C
Erosional surface with tilted beds below
Analysis & Theory
Angular unconformities show tilted or folded beds overlain by flat-lying strata.
The **fold axis** is:
B
The central point of curvature
C
The direction of bending
Analysis & Theory
Fold axis is the line that runs along the crest or trough of a fold.
Which of the following is a **linear structure** in folded rocks?
Analysis & Theory
Hinge line represents the line of maximum curvature on a fold.
The **axial plane** of a fold is:
B
The plane dividing the limbs of the fold
Analysis & Theory
Axial plane divides the fold into two limbs and passes through the hinge lines.
Which fault type places **older rocks over younger**?
Analysis & Theory
Thrust faults result in older strata overriding younger beds.
Joints are generally oriented:
C
Perpendicular to bedding planes
Analysis & Theory
Joints often form perpendicular to bedding planes due to contraction or stress.
Conjugate joints are formed due to:
Analysis & Theory
Conjugate joints are formed in pairs under compressive or shear stress.
The zone where a fault occurs is called a:
Analysis & Theory
Shear zone is a region of intense deformation along a fault plane.
Domes and basins are types of:
Analysis & Theory
Domes (upward bulges) and basins (downward sinks) are structural folds.
What causes unconformities in rock records?
C
Erosion and non-deposition
Analysis & Theory
Unconformities are gaps in the rock record due to erosion or lack of deposition.
In which structure is the oldest rock in the center?
Analysis & Theory
Domes expose older rocks in the center due to uplift.
What is the primary difference between a fault and a joint?
B
Joints form under pressure
C
Faults involve movement, joints don’t
D
Joints are underground only
Analysis & Theory
Faults involve displacement; joints are simple fractures without movement.