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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
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