Geology 101 - Introduction to Physical Geology
Course Information
Basics
BasicsTables
Glossary
Grading Rubrics
Labs
Term Projects
Tables of Geologic Map Symbols
Table of Strikes & Dip Symbols
Table of Fault Symbols
Table of Fold Symbols
Strike and Dip Symbols
Strike and dip are a way of representing the three-dimensional
orientation of a planar surface on a two-dimensional map. The strike is
the compass direction of a horizontal line on the plane. All the
horizontal lines on a plane are parallel, so they all have the same
characteristic compass direction. The dip is the angle at which the
plane slopes downhill from the horizontal, at its maximum slope, which
is at right angles (90�) from strike.
Map
Definition Explanation of symbol
Symbol
strike (longer line) is horizontal line
on bedding plane
strike and strike parallels nearby contacts
dip of beds between stratified rocks
other than dip shows which way beds run
horizontal or downhill
vertical dip angle, number at end of dip
symbol, is how much beds tilt down
from horizontal
because the bed is horizontal it
horizontal strikes in all directions
beds because the bed is horizontal, the dip
is 0%
strike (longer line) is horizontal line
on bedding plane
strike and because the bed dips vertically (has
dip of a 90% dip), it dips equally in either
vertical beds direction at right angles to strike, so
the dip line is shown extending in
both directions
Geologic Fault Symbols
Type of
Type of Map Geologic
Definition Regional
Fault Symbol Associations
Stress
zones of
crustal
extension
divergent
plate
hanging wall boundaries
normal tension
down, footwall up edges of
horsts and
grabens
Basin and
Range
region
low-angle normal boundaries
fault, footwall - of
detachment gneiss, hanging tension metamorphic
wall - shallow- core
crust rocks complexes
zones of
crustal
compression
thrust hanging wall up, compression convergent
footwall down plate
boundaries
zones of
crustal
high-angle (45° or
compression
reverse more dip) thrust compression
convergent
fault
plate
boundaries
continental
margins
undergoing
rocks on either
oblique (not
side move
straight on)
strike-slip horizontally in shear
plate
opposite
convergence
directions
transform
plate
boundaries
orogenic
mountain
belts
continental
combines
margins
oblique-slip horizontal and combination
undergoing
vertical motion
oblique (not
straight on)
plate
convergence
Geologic Fold Symbols
Type of Map Appearance of Beds in
Definition
Fold Symbol Map View
roughly parallel stripes
dip away from center
(away from axis)
anticline up fold oldest at center (along
axis)
youngest farthest from
center
roughly a U-shaped
pattern
plunges in direction U
plunging points
up fold with tilted axis
anticline oldest at center (along
axis)
youngest farthest from
center
roughly parallel stripes
dip toward center
(toward axis)
syncline down fold oldest farthest from
center
youngest at center
(along axis)
roughly a U-shaped
pattern
plunges in direction U
plunging down fold with tilted opens
syncline axis oldest farthest from
center
youngest at center
(along axis)
strata tilted in one all dip in same
monocline
direction direction
roughly a bull's eye
pattern
structural upward bulge in dip away from center
dome layered rocks oldest in center
youngest farthest from
center
roughly a bull's eye
pattern
structural downward bulge in dip toward center
basin layered rocks youngest in center
oldest farthest from
center
« Back to TOP
Course Information | Basics | Basics Tables | Glossary | Grading Rubrics | Labs | Term Projects
Geology 101 - Introduction to Physical Geology
Basics Table--Geologic Map Symbols
Created by Ralph L. Dawes, Ph.D. and Cheryl D. Dawes, including figures unless otherwise noted
updated: 7/10/11
Unless otherwise specified, this work by Washington State Colleges is licensed under a Creative
Commons Attribution 3.0 United States License.
