1.
GEOLOGIC MAPPING
2014 EVENT OVERVIEW

2.
MARK A. VANHECKE
NATIONAL SCIENCE OLYMPIAD
EARTH-SPACE SCIENCE EVENT CHAIR
PRESENTED BY:
mvanhecke@comcast.net

3.
PRESENTATION OBJECTIVES:
Identify event parameters for the 2014
Geologic Mapping Event
Identify the basic features of geologic
maps
Use a geologic map diagram to
construct a cross section and project
map features
Interpret a block diagram and order
rock strata from oldest to youngest

4.
EVENT OVERVIEW
2014 GEOLOGIC MAPPING

5.
2014 EVENT OVERVIEW
Identify basic features of geologic
maps
Interpret geologic map features
including intrusions, subsurface
geometries, deformation features and
subsurface depositional features
Identify folds, fault types and erosional
patterns
Construct fault sections, topographic
profiles, projections of mapped
features

6.
2014 EVENT OVERVIEW
Identify structural elements shown in
geologic maps including synforms,
antiforms, basins, monoclines, domes
and saddles
Determine bed thicknesses, true dip
and orientations of planes from point

7.
WHAT IS A GEOLOGIC MAP?
2014 GEOLOGIC MAPPING

8.
WHAT ARE GEOLOGIC MAPS?
A geologic map shows: Mappable Rock Layers
Mappable sediment layers
that cover up the rocks
Geologic structures
including folds, faults and
intrusions
‘Mappable’ rock layers are
recognized consistently across a
landscape

9.
WHAT ARE GEOLOGIC MAPS?
Mappable units of rock and sediment may be identified
using letter symbols

10.
WHAT ARE GEOLOGIC MAPS?
Mappable units of rock and sediment may also use
colors, patterns or combinations of letter symbols and
colors/patterns

11.
GEOLOGY AND GEOLOGIC HISTORY

12.
PRACTICAL APPLICATIONS

13.
NATURAL RESOURCES

14.
GEOHAZARDS

15.
GROUNDWATER

16.
BASIC FEATURES
OF GEOLOGIC MAPS
2014 GEOLOGIC MAPPING

17.
GEOLOGIC MAPS

18.
BASIC FEATURES OF GEOLOGIC MAPS
The basic features of a geologic map are the map itself
and the legend or key used to explain the symbols,
colors/patterns

19.
STRATIGRAPHIC COLUMNS

20.
CROSS SECTIONS

21.
BLOCK DIAGRAMS

22.
DRAWING A CROSS SECTION
2014 GEOLOGIC MAPPING

23.
DRAWING A GEOLOGIC CROSS SECTION
A geologic map identifies different rock types
and where they can be seen on the surface

24.
DRAWING A GEOLOGIC CROSS SECTION
A cross section of a geologic map is a vertical
slice of the Earth’s surface that shows what
the underlying geologic structure at that
location looks like

25.
DRAWING A GEOLOGIC CROSS SECTION
A cross section of a geologic map also shows
the boundaries between different types of rock
found on the surface

26.
DRAWING A GEOLOGIC CROSS SECTION
A cross section of a geologic map also shows
the orientation of rock layers where they
intersect the surface.
The orientation or direction of rock layers is
expressed as Strike and Dip.

27.
DRAWING A GEOLOGIC CROSS SECTION
Strike refers to the compass bearing
(direction) of a line formed by the intersection
of a horizontal plane and an inclined layer of
rock.
N
NE
SW
Angle of the strike
is from NE to SW
In a strike-dip symbol, the larger line refers to the
Strike

28.
DRAWING A GEOLOGIC CROSS SECTION
Dip refers to the angle between a horizontal
plane and the inclined stratum of rock, fault or
fracture
45º
Horizontal Plane
Dip Direction

29.
DRAWING A GEOLOGIC CROSS SECTION
In a strike-dip symbol, the smaller line indicates Dip
45

30.
DRAWING A GEOLOGIC CROSS SECTION
The location of the dip line in relation to the strike
line indicates the direction of the dip.
45
Rock layer dips to the
east
24
Rock layer dips to
the west

31.
DRAWING A GEOLOGIC CROSS SECTION
Solve the strike and dip problems given on Worksheet 1
Section 1

32.
WORKSHEET 1: SECTION 1 ANSWERS
40
40
35
40
35
Strike
Dip
East
West
East
SE NW
SE

33.
DRAWING A GEOLOGIC CROSS SECTION
Strike and Dip is usually expressed in bearings
(Quadrants)

34.
DRAWING A GEOLOGIC CROSS SECTION
Writing strike and dip coordinates
24
Strike= N45ºW
Dip= 24ºSW
43
Strike= N90ºE
Dip= 43ºN

35.
DRAWING A GEOLOGIC CROSS SECTION
On Worksheet 1 Section 2 measure the angle of strike
and write out the bearings for the strike and dip
measurements given

36.
WORKSHEET 1: SECTION 2 ANSWERS
52
38
Strike = N44ºW (or S44ºE)
Dip= 52ºSW
Strike= N82ºE (or S82ºW)
Dip= 38ºNW

37.
DRAWING A GEOLOGIC CROSS SECTION
STEP 1 On Worksheet 2, draw a horizontal line just
below the diagram as shown below

38.
DRAWING A GEOLOGIC CROSS SECTION
STEP 2 Transfer all available information from the
diagram as shown to the line you just drew.

39.
DRAWING A GEOLOGIC CROSS SECTION
STEP 3 Indicate the locations of boundaries
between layers on the horizontal line as
shown

40.
DRAWING A GEOLOGIC CROSS SECTION
STEP 4 Use a protractor to measure the direction
and angle of the dip and draw a small line
on the horizontal line for each as shown

41.
DRAWING A GEOLOGIC CROSS SECTION
How are different outcrops of the same layer
connected?
How do dip angles and directions change
above and below the surface?

42.
DRAWING A GEOLOGIC CROSS SECTION
STEP 5 Connect the boundary lines for each layer
as shown

43.
PRINCIPLES
OF STRATIGRAPHY
2014 GEOLOGIC MAPPING

44.
INTERPRETING
A BLOCK DIAGRAM
2014 GEOLOGIC MAPPING

45.
INTERPRETING A BLOCK DIAGRAM
Block diagrams show different rock strata and changes
that have been made over time to their layering

46.
INTERPRETING A BLOCK DIAGRAM
Fault
Original Horizontality
Superposition
Igneous Intrusion
Nonconformity

47.
INTERPRETING A BLOCK DIAGRAM

48.
INTERPRETING A BLOCK DIAGRAM
OLDEST YOUNGEST

49.
INTERPRETING A BLOCK DIAGRAM
Original Horizontality
Superposition
Angular Disconformity
Disconformity
Igneous Intrusions Faults
Nonconformity

50.
INTERPRETING A BLOCK DIAGRAM

51.
INTERPRETING A BLOCK DIAGRAM
OLDEST YOUNGEST

52.
RESOURCES
2014 GEOLOGIC MAPPING

53.
RESOURCES
http://geomaps.wr.usgs.gov/parks/gmap/gmap3.html
USGS Geologic Maps. An excellent discussion of strike
and dip. It also provides a good introduction to map
keys.
http://www.wwnorton.com/college/geo/geolab/animations.
aspx
This web-based Norton Publishing Lab Manual for
Introductory Geology is filled with animations that show
the movements of geologic features that are identified on
many maps
http://www.youtube.com/watch?v=ZZHgxlh0PQ4
Excellent Video Series I used for the Block Diagram
Activities (three parts to series)
http://www.youtube.com/watch?v=Vgo8Z63n60g
Excellent description of drawing a Cross Section I used
for this activity