1. GY403 Structural Geology Lab
Thickness and Depth Problems

2. Special Case: horizontal attitude
Note: geological contacts will parallel topographic contour lines on map.
93 ft.
87 ft.
T=93-87 = 6 ft.
Thickness (t) =
Elev. Upper contact – Elev. Lower contact

3. Special Case: vertical attitude
Note: cross-section is perpendicular to strike of unit. Thickness = outcrop width in this case. w
General Rule: If the dip (δ) of the unit is perpendicular to the ground surface then w = t. δ t

4. perpendicular to strike of strata
NOTE: cross section is
perpendicular to strike of
strata
w= true outcrop width δ
t= true thickness

5. N β Cos β = (w) / (w’) w = Cos β * (w’) w’ = apparent outcrop width40
w = true
outcrop width 40

6. w σ δ t West East Scenario: slope and dip are
inclined in opposite directions
West-facing slope w σ δ t δ
= true dip angle σ
= slope angle
Sin( δ + σ
) = t/w
t = Sin( δ + σ
) * w
Note: cross-section must be
perpendicular to strike of bedding

7. w σ t δ δ - σ West East Scenario: slope and dip are East-facing slope
inclined in same direction w δ
= true dip angle δ - σ σ
= slope angle σ t δ
Sin( δ - σ
) = t/w
t = Sin( δ - σ
) * w
Note: cross-section must be perpendicular to strike of bedding,
and slope angle ( σ
) must be measured perpendicular to strike.

8. perpendicular to strike of strata
NOTE: cross section is
perpendicular to strike of
strata
w= true outcrop width δ δ t
d= depth in
vertical drill
hole
Cos ( δ
) = t / d
d = t / Cos( δ )