Mapwork terms

Question 1

Angular unconformity

Answer 1

An unconformity surface with the beds above non-parallel to the beds below.

Question 2

Anticline

Answer 2

A fold with the oldest rocks in the core; usually arch shaped

Question 3

Apparent dip

Answer 3

The angle of dip of a surface measured in the direction other than the line of greatest slope

Question 4

Attitude

Answer 4

The ‘3D orientation’ of a line or plane

Question 5

Axial plane of a fold

Answer 5

The plane containing successive hinge lines of the folded surfaces

Question 6

Axial trace of a fold

Answer 6

The intersection of the fold axial plane with the ground surface

Question 7

Axis of a fold

Answer 7

The direction in space parallel to the hinge lines, but without any particular position on the fold

Question 8

Bedding

Answer 8

accumulation surfaces in sedimentary or volcanic rocks; often originally sub-horizontal

Question 9

Geological boundary

Answer 9

line of intersection of a geological contact with the ground surface

Question 10

Cleavage (rock)

Answer 10

Alignment of minerals in a metamorphic rock (due to heat and pressure) promotion a tendency to fracture

Question 11

Geological contact

Answer 11

Planar surface between 2 geological units; may be stratigraphic or faulted

Question 12

structural contour

Answer 12

lines joining points of equal height in a geological surface

Question 13

topographic contour

Answer 13

lines joining points of equal height on the ground surface

Question 14

core of a fold

Answer 14

the concave inner arc of the fold

Question 15

cross-section

Answer 15

the trace of geology and topography on a planar cut through the earth, usually vertical

Question 16

dextral fault

Answer 16

a fault where the far side is displaces to the right with respect to the near side

Question 17

True dip

Answer 17

The angle between the line of greatest slope in a surface and the horizontal projection of the line

Question 18

Direction of dip

Answer 18

the angle between north and the horizontal projection of the line of greatest slope in a surface

Question 19

Dip-slip fault

Answer 19

A fault with displacement up and down the dip of the fault plane

Question 20

Downthrow side of a fault

Answer 20

the side which is displaces downward relative to the other

Question 21

drift map

Answer 21

geological map showing essentially Quaternary rocks

Question 22

fault

Answer 22

fracture with appreciable shear displacement across it

Question 23

fold

Answer 23

a curviplanar geometry of originally planar geological units

Question 24

hinge line

Answer 24

a line joining points of maximum curvature on a fold

Question 25

inlier

Answer 25

an outcrop of older rock completely surrounded by younger rocks

Question 26

normal fault

Answer 26

A fault that dips towards its downthrow site

Question 27

outcrop

Answer 27

the intersection of geological units or structures with the ground surface, even if covered by a thin veneer of superficial sediments

Question 28

outlier

Answer 28

an outcrop of younger rocks completely surrounded by older rocks

Question 29

parallel unconformity

Answer 29

an unconformity surface with beds above parallel to the beds below

Question 30

plunge of a line

Answer 30

the angle between a line and its horizontal projection

Question 31

reverse fault

Answer 31

a fault that tips towards its upthrow site

Question 32

Sinistral fault

Answer 32

a fault where the far side is displaced to the left with respect to the near side

Question 33

solid map

Answer 33

geological map showing essentially pre-Quaternary rocks

Question 34

stratigraphic contact

Answer 34

a contact between geological units resulting from their original accumulation rather than later faulting

Question 35

stratigraphic throw of a fault

Answer 35

the difference in vertical height across a fault of structure contours for the same contact

Question 36

strike of a surface

Answer 36

the angle (usually measured clockwise) between north and the horizontal line in a surface

Question 37

strike line

Answer 37

line on a map parallel to the strike of a surface at that point; equivalent to a structure contour if structure contours are straight

Question 38

strike separation of a fault

Answer 38

the horizontal difference along the fault between the ends of two like contours on either side

Question 39

strike-slip fault

Answer 39

a fault with displacement along the strike of the fault plane

Question 40

geological structure

Answer 40

geometrical arrangement of rocks, e.g. folds, faults

Question 41

subcrop map

Answer 41

a map of the rocks immediately below an unconformity surface

Question 42

Syncline

Answer 42

a fold the youngest rocks in its core; usually trough shaped

Question 43

stratigraphic thickness

Answer 43

distance between the bounding contacts of a geological unit, measured perpendicularly to the contacts

Question 44

vertical thickness

Answer 44

vertical distance between the bounding contacts of a geological unit

Question 45

topographic profile

Answer 45

the trace of the ground surface on a cross-section

Question 46

topography

Answer 46

geographical features of ground surface

Question 47

trend of a line

Answer 47

the angle (measured clockwise) between north and the horizontal projection of the line

Question 48

unconformity

Answer 48

a geological surface representing a gap in time during deposition of a geological sequence

Question 49

geological unit

Answer 49

3D rock body, distinct in rock type from adjacent units

Question 50

upthrow side of a fault

Answer 50

the side which is displaced upward relative to the other

Question 51

V-ing

Answer 51

the V-shaped pattern made by boundaries of dipping units as they cross ridges or valleys. The points of the V usually points up-dip on a ridge and down-dip in a valley