Geological Structures Flashcards
Dip
Maximum inclination of a bed measured from the horizontal
Strike
The horizontal line in a bedding plane measured as a bearing from North
Stress
The force applied to rocks
Strain
A change in the shape of a body as a result of applied stress
Competent rock
Rock that stat the same thickness when decried and react in a brittle way
Incompetent rock
Vary in thickness when deformed as they behave plastically
Plastic
Stress and strain are not directly proportional
Elastic
Stress is proportional to strain
Uncomformities
Represent a period where no sediment was deposited
Joints
A fracture in competent rock along which no observable movement has occurred
Faults
Brittle fractures where there is a displacement which can be horizontal or vertical
Fault plane
A plane of fracture along which the rocks have been displaced
Upthrow
The side of the fault where the movement is upwards in relation to the other side
Downthrow
The side of the fault where the movement is downward in relation to the other side
Throw
The vertical displacement of the roads along the fault plane
Footwall
The side of the fault that is below the fault plane of the fault is not vertical
Hanging wall
The side of the fault that was above the max inclination of the fault plane as measured from the horizontal
Anticline
An upright fold with the oldest rocks in the centre
Anti form
A upward closing fold
Syncline
A downward closing fold with youngest rocks in the core
Synform
A downward closing fold
Fold limb
The section of a fold between 1 hinge and the next forming the side of the fold
Hinge
The line along which there is a change in the amount of dip forming the most sharply curved part of the fold
Crest
The highest point of a folded bed
Trough
The lowest part of a folded bed
Axial plane
A plane that joins the hinges of all the beds
Axial plane trace
The outcrop of the axial plane at the earths surface
Plunge
The angle of dip of the axial plane from the horizontal
Dome
An anticline which dips away from the centre in all directions
Basin
A syncline which dips towards the centre from all directions
Overfolds
Folds which have both fold limbs dipping in the same direction by different amounts
Recumbent
Folds that have axial planes and fold limbs which close at the horizontal
Nappe
Recumbent folds that are broken along thrust planes
Isoclinical
Folds have parallel limbs that are nearly vertical and in very tight folds
