EART 109 Introduction to Field Geologycrowe/ES109/lectures/Lecture 1 Images.pdfDDDº MM.MMM’ (E or W) E or W refers to position relative to the Prime Meridan which passes through

EART 109EART 109Introduction to Field GeologyIntroduction to Field Geology

Instructors: Paul Koch; Instructors: Paul Koch; Christie RowChristie RowTAs: TAs: Jon Perkins, Erin ToddJon Perkins, Erin ToddUG Assistants: UG Assistants: Lia LajoieLia Lajoie, Kevin Walker, Kevin Walker

What is a Geologic Map?What is a Geologic Map?

A 2 dimensional description of the distribution of rock units, thecontacts between them, often with structural features defined byrock units and geomorphic features.

Know:

* Geological provinces of California; basic geology andhistory of each.

* Fundamental principles of stratigraphy (e.g. superposition,cross-cutting, etc.).

* Concepts and nomenclature for topographic and geologicalmaps.

* Some basic structural terms (faults, folds) and their linearand planar elements.

* Basic classification and origins for main types ofsedimentary, igneous and metamorphic rocks.

* Detailed local knowledge of field trip sites. * The Phanerozoic timescale.

Objectives of this classObjectives of this class

Are able to:

* Describe the essential textures and mineralogy of anycommon rock hand sample; ability to identify commonrocks and interpret their origins.

* Measure planar and linear elements with a geologiccompass.

* Find accurate locations on a topographic map; accuratelyplace and record geologic observations on the map.

* Identify some geologic features in the field (faults, folds,bedding, sedimentary structures, etc.).

* Measure and record a stratigraphic section. * Interpret geologic map data into the 3rd dimension (cross

section interpretation). * Complete key products in geology (geologic map, cross

section, report).

Objectives of this classObjectives of this class

Have acquired these transferable skills

* Clear, concise thinking recorded in scientific report writing. * Recording qualitative and quantitative observations in a

transferable form (field note-taking). * Clear separation of data and interpretation, and of one's

own or other's data and interpretations. * Ability to read, assess, and interpret information from

published sources. * Awareness of problem solving pathways and culture of

scientific inquiry.

Objectives of this classObjectives of this class

The Geographic GridThe Geographic Grid

Spherical CoordinatesSpherical CoordinatesLatitude Latitude N-S position N-S position

Longitude Longitude E-W position E-W position

LatitudeLatitude Parallels of latitudeParallels of latitude are all small circles, are all small circles,

except for the equator.except for the equator.•• True east-west linesTrue east-west lines•• Always parallelAlways parallel•• Any two are always equal distances apartAny two are always equal distances apart•• An infinite number can be createdAn infinite number can be created•• Parallels are related to the horizontal x-Parallels are related to the horizontal x-

axes of the Cartesian coordinate system.axes of the Cartesian coordinate system.

LongitudeLongitude Meridians of longitudeMeridians of longitude are halves of great are halves of great

circles, connecting one pole to the other.circles, connecting one pole to the other.•• All run in a true north-south directionAll run in a true north-south direction•• Spaced farthest apart at the equator andSpaced farthest apart at the equator and

converge to a point at the polesconverge to a point at the poles•• An infinite number can be created on aAn infinite number can be created on a

globeglobe•• Meridians are similar to the vertical y-Meridians are similar to the vertical y-

axes of the Cartesian coordinate system.axes of the Cartesian coordinate system.

Latitude and LongitudeLatitude and Longitude

LONGITUDELONGITUDE

Expressed as:Expressed as:

DDDº MMDDDº MM’’ SS SS”” (E or W) (E or W)oror

DDDº MM.MMMDDDº MM.MMM’’ (E or W) (E or W)

E or W refers to position relativeE or W refers to position relativeto the to the Prime Prime MeridanMeridan whichwhichpasses through Greenwichpasses through GreenwichEnglandEngland

LATITUDELATITUDE

Expressed as:Expressed as:

DDº MMDDº MM’’ SS SS”” (N or S) (N or S)oror

DDº MM.MMMDDº MM.MMM’’ (N or S) (N or S)

N or S references to positionN or S references to positionrelative to the relative to the EQUATOREQUATOR

UC SANTA CRUZ

Approximately:

37º 0037º 00’’ N N

122º 03122º 03’’ W W

E & MS Bldg.

UC SANTA CRUZ

Approximately:

36º 5936º 59’’ 56 56”” N N

122º 03122º 03’’ 36 36”” W W

Universal TransverseUniversal TransverseMercator Mercator (UTM) Grid(UTM) Grid

UTM Zones in the US

UTM Minimizes Distortion

GN Refers to Grid North

Grid SystemsGrid Systems

Geographical Grid (Latitude/Longitude)Geographical Grid (Latitude/Longitude) Universal Transverse Universal Transverse MercatorMercator State Plane Coordinate SystemState Plane Coordinate System United States Public Land SurveyUnited States Public Land Survey

ProjectionsProjections

Problem: Earth is [nearly]* spherical so aProblem: Earth is [nearly]* spherical so amap cannot be projected onto a 2Dmap cannot be projected onto a 2Dsurface without some distortionsurface without some distortion

Example Example Mercator Mercator Projection:Projection:

* Earth is an oblate spheroid. Distance from center to pole is 0.3%less than center to equator (more later).

Compare DistortionCompare Distortion

MERCATOR PROJECTION SINUSOIDAL PROJECTION

Projections (See reader)Projections (See reader)

GlobeGlobe MercatorMercator Lambert Lambert Azimuthal Azimuthal Equal AreaEqual Area Albers Equal Area ConicAlbers Equal Area Conic PolyconicPolyconic Lambert Conformal ConicLambert Conformal Conic Space Oblique Space Oblique MercatorMercator GnomicGnomic Oblique Oblique MercatorMercator Transverse Transverse MercatorMercator OrthographicOrthographic SterographicSterographic

Other than GlobeGlobe, all have distortions…tend to beminimize closest to center of projection and atlarger larger map scales

MapsMaps

Need three things to uniquely located you on theNeed three things to uniquely located you on theEarthEarth’’s surface:s surface:•• Latitude (N-S position) or Northing (UTM)Latitude (N-S position) or Northing (UTM)•• Longitude (E-W position) or Easting (UTM)Longitude (E-W position) or Easting (UTM)•• Elevation (relative some Datum (e.g. WGS84))Elevation (relative some Datum (e.g. WGS84))

Map InformationMap Information•• Scale (Fractional Scale, Scale Bar, Verbal Scale)Scale (Fractional Scale, Scale Bar, Verbal Scale)•• North ArrowNorth Arrow•• DatumDatum•• ProjectionProjection

DatumDatum

Model that describes the actual shapeModel that describes the actual shapeof the earth. Note the differenceof the earth. Note the differencebetween polar and equatorial radiibetween polar and equatorial radii

Units = meters

Map ScaleMap Scale Fractional ScaleFractional Scale: What does 1:24000 mean?: What does 1:24000 mean?

•• 1 of anything on the map equals 24000 of anything in reality1 of anything on the map equals 24000 of anything in reality•• 11”” = 24,000 = 24,000”” = 2000 = 2000’’

Large ScaleLarge Scale•• 1:12,000 1:12,000 1 1””=1000=1000•• Covers a smaller areaCovers a smaller area

Small ScaleSmall Scale•• 1:5,000,000 1:5,000,000 1 cm = 50 km 1 cm = 50 km•• Covers a huge areaCovers a huge area

Verbal scaleVerbal scale: 1:62,500, or: 1:62,500, or 1 inch is approximately 1 mile.1 inch is approximately 1 mile.

Maps should have a Maps should have a Scale BarScale Bar so that if they are reduced so that if they are reducedor enlarged they still carry distance information.or enlarged they still carry distance information.

North ArrowsNorth Arrows

GNMN

**

* = True North

GN Grid North

MN Magnetic North

Shows Declination (more later)

Topographic mapsTopographic maps

TopographyTopography•• Topo Topo (from Greek (from Greek topostopos –– meaning place) meaning place)•• Graphy Graphy (from Greek (from Greek graphiagraphia –– meaning writing or meaning writing or

description)description)

Topographic Map contains a 3D description ofTopographic Map contains a 3D description oflandforms in 2Dlandforms in 2D

A description of the distribution of elevations isA description of the distribution of elevations isgiven by given by Contour LinesContour Lines

Contour lines connect points of equal elevationContour lines connect points of equal elevation

http://reynolds.asu.edu/topo_gallery/intro_start.htm

Visualizing TopographyVisualizing Topography

GeomagnetismGeomagnetism

The The GeodynamoGeodynamo: Sustains: Sustainsthe Earththe Earth’’s Magnetic Fields Magnetic Field

Field orientation at a pointField orientation at a point

Magnetic FieldMagnetic Field•• InclinationInclination

Deviation fromDeviation fromHorizontalHorizontal

•• DeclinationDeclination Deviation fromDeviation from

geographic northgeographic north

•• PolarityPolarity Direction ofDirection of

magnetic fluxmagnetic flux

MagneticNorth (2005)

82.7 ºN

114.4 ºW

DeclinationDeclination

Red = east; Blue = west

InclinationInclination

PaleomagnetismPaleomagnetism•• Inclination givesInclination gives

paleolatitudepaleolatitude

•• Important forImportant fortectonics studiestectonics studies

PolarityPolarity

Crucial for recognition of sea floorspreading. Key to plate tectonics.

Polarity reversal time scale

Geologic Field MethodsGeologic Field Methods

We exploit the EarthWe exploit the Earth’’s magnetic field in twos magnetic field in twoways in this class.ways in this class.

LocationLocation and and NavigationNavigation: : keepkeepourselves located on a topographic baseourselves located on a topographic basemap.map.

AttitudesAttitudes: measure attitudes of rocks,: measure attitudes of rocks,structural features (next time).structural features (next time).

Location - NavigationLocation - Navigation

Compass Bearing

Triangulation

Know the features ofyour Brunton….

You will get a lot ofpractice

2.1 Needle (white or N) points to Mag North2.1 Needle (white or N) points to Mag North 2.2 Graduated circle (quadrant or 0-360 azimuth)2.2 Graduated circle (quadrant or 0-360 azimuth) 2.3 Zero Pin2.3 Zero Pin 2.4 Large sight2.4 Large sight 2.5 Small sight2.5 Small sight 2.6 Mirror2.6 Mirror 2.7 Round Level (for making compass horizontal)2.7 Round Level (for making compass horizontal) 2.8 Vernier (Clinometer Measurements)2.8 Vernier (Clinometer Measurements) 2.9 Long Level (Clinometer Measurements)2.9 Long Level (Clinometer Measurements)

2.10 Circle Adjusting Screw (Correct for2.10 Circle Adjusting Screw (Correct forDeclination)Declination)

2.11 Vernier Adjustment (Inclination (dip)2.11 Vernier Adjustment (Inclination (dip)measurements)measurements)

2.12 Ball and Socket Tripod Mount2.12 Ball and Socket Tripod Mount Alidade Mount (Plastic Models)Alidade Mount (Plastic Models)

Brunton Brunton MechanicsMechanicsFirst things first: First things first: SET YOUR DECLINATION!!!SET YOUR DECLINATION!!!