GEOLOGIC MAPPING

2014 EVENT OVERVIEW

MARK A. VANHECKENATIONAL SCIENCE OLYMPIADEARTH-SPACE SCIENCE EVENT CHAIR

PRESENTED BY:

mvanhecke@comcast.net

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

EVENT OVERVIEW2014 GEOLOGIC MAPPING

2014 EVENT OVERVIEWIdentify 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

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

WHAT IS A GEOLOGIC MAP?2014 GEOLOGIC MAPPING

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

WHAT ARE GEOLOGIC MAPS?

Mappable units of rock and sediment may be identified using letter symbols

WHAT ARE GEOLOGIC MAPS?

Mappable units of rock and sediment may also use colors, patterns or combinations of letter symbols and colors/patterns

GEOLOGY AND GEOLOGIC HISTORY

PRACTICAL APPLICATIONS

NATURAL RESOURCES

GEOHAZARDS

GROUNDWATER

BASIC FEATURESOF GEOLOGIC MAPS

2014 GEOLOGIC MAPPING

GEOLOGIC MAPS

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

STRATIGRAPHIC COLUMNS

CROSS SECTIONS

BLOCK DIAGRAMS

DRAWING A CROSS SECTION2014 GEOLOGIC MAPPING

DRAWING A GEOLOGIC CROSS SECTION

A geologic map identifies different rock types and where they can be seen on the surface

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

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

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.

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.

NNE

SW

Angle of the strike is from NE to SW

In a strike-dip symbol, the larger line refers to the Strike

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

Strike

Line

Dip Direction

DRAWING A GEOLOGIC CROSS SECTION

In a strike-dip symbol, the smaller line indicates Dip

45

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

DRAWING A GEOLOGIC CROSS SECTION

Solve the strike and dip problems given on Worksheet 1 Section 1

WORKSHEET 1: SECTION 1 ANSWERS

4040

35

50

40

35

50

Strike

Dip

East

West

East

SE NWSE

DRAWING A GEOLOGIC CROSS SECTION

Strike and Dip is usually expressed in bearings (Quadrants)

DRAWING A GEOLOGIC CROSS SECTION

Writing strike and dip coordinates

24

Strike= N45ºW

Dip= 24ºSW

43

Strike= N90ºE

Dip= 43ºN

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

WORKSHEET 1: SECTION 2 ANSWERS

52

38

Strike = N44ºW (or S44ºE)Dip= 52ºSW

Strike= N82ºE (or S82ºW)Dip= 38ºNW

DRAWING A GEOLOGIC CROSS SECTION

STEP 1 On Worksheet 2, draw a horizontal line just below the diagram as shown below

DRAWING A GEOLOGIC CROSS SECTION

STEP 2 Transfer all available information from the diagram as shown to the line you just drew.

DRAWING A GEOLOGIC CROSS SECTION

STEP 3 Indicate the locations of boundaries between layers on the horizontal line as shown

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

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?

DRAWING A GEOLOGIC CROSS SECTION

STEP 5 Connect the boundary lines for each layer as shown

PRINCIPLES OF STRATIGRAPHY

2014 GEOLOGIC MAPPING

INTERPRETINGA BLOCK DIAGRAM

2014 GEOLOGIC MAPPING

INTERPRETING A BLOCK DIAGRAM

Block diagrams show different rock strata and changes that have been made over time to their layering

INTERPRETING A BLOCK DIAGRAM

Fault

Original Horizontality

Superposition

Igneous Intrusion

Nonconformity

INTERPRETING A BLOCK DIAGRAM

INTERPRETING A BLOCK DIAGRAM

OLDEST YOUNGEST

INTERPRETING A BLOCK DIAGRAM

Original Horizontality

Superposition

Angular Disconformity

Disconformity

Igneous Intrusions Faults

Nonconformity

INTERPRETING A BLOCK DIAGRAM

INTERPRETING A BLOCK DIAGRAM

OLDEST YOUNGEST

RESOURCES2014 GEOLOGIC MAPPING

RESOURCEShttp://geomaps.wr.usgs.gov/parks/gmap/gmap3.htmlUSGS 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.aspxThis 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=ZZHgxlh0PQ4Excellent Video Series I used for the Block Diagram Activities (three parts to series)

http://www.youtube.com/watch?v=Vgo8Z63n60gExcellent description of drawing a Cross Section I used for this activity