Why do we have continuing education requirements for Professional Geologists?
Excerpted from an Amplified Record of Experience for a PG Licensing examination application submitted in 2011The [activity] revealed extensive soil and GW contamination. MWs were installedinto the Precambrian felsic gneiss overburden and sampled.MWs were installed into the ----------- Wissahickon saprolite to determine theextent of the GW plume. The -------- Wissahickon sediments accumulated in a riftbasin on top of Laurentian continental crust and consists of muscovite andtourmaline-apatite-staurolite-kyanite-garnet-bearing metamorphic mineralassemblages.
Representative Elemental VolumeThe size of an REV, therefore, must be larger than the scale of microscopicheterogeneities created by individual geometries of the solid phase particlesand void spaces, and much smaller than the scale of the domain of interest.It is the heterogeneity within the domain of interest which counts whendetermining the size of the REV. Bear, 1993
Resolution of the Field Hydraulic Gradient in a Sub-Vertical PlaneThe upper surface of the water table as resolved into the plane occurs at anin-plane gradient equal to the apparent dip observed in that plane. In such a case, the magnitude of the field hydraulic gradient is greater than the magnitude of the resolved hydraulic gradient.
Resolution of the Field Hydraulic Gradient in a Sub-Vertical PlaneThe only exception to that general condition is where the strike of theplane is coincident with the azimuth of the flow vector in which caseflow would be precisely parallel to strike and the field gradient wouldbe equal to the in-plane gradient.
STRIKE & DIPSTRIKE = trend (azimuth, bearing) Another definition of Strike =of a structural contour on a plane. trend of a line connecting points of equal elevation on a plane.………of a horizontal line on aplane.……….water level line on a plane.In the field this horizontal line isdefined by using bulls eye level to On a plane, structural contourshold compass as a horizontal plane will be straight lines with equaland placing edge of compass against spacing – and all are parallel tosurface to be measured. strike.Hence measuring strike of a plane isthe determination of a structural Source: Donald Wisecontour line on the plane.
STRIKE & DIPDIP = the angle from the horizontal to theplane as measured in a planeperpendicular to strike (or perpendicularto a structural contour) .NOTE: Dip must be measured in thevertical plan (compass must be held invertical plane).Dip is measured in direction of maximuminclination ( normal to strike)Measured in any direction other thannormal to strike, one measures anAPPARENT DIP which is somewhat lessthan true dip.NOTE: Apparent dip on any planemeasured parallel to strike is 0. (i.e. thedip on a structural contour is zero) Source: Donald Wise
REPRESENTATION OF A PLANE ON A MAP. Ideal is structural contours on the plane (for a true planar surface they are straight lines with equal spacing and all parallel to each other).MAPSVertical plane 1000, 2000, 3000 contours all in same place.Closer the spacing of the structural contours the steeper the dip of the plane.Vertical plane has all the contours at the same place.Commonly we only measure a tiny bit of the total plane and hence use the symbol If we are measuring a parallel set of planes (pile of dipping sediments) they all will have the same strike and dip. Source: Donald Wise
DETERMINING DIP FROM STRUCTURALCONTOURS - RIGHT SECTIONSA right section is a view of theplane running along a line atright angles to strike.Draw some convenient line (AB)perpendicular to strike.Draw line AB off the map,marking off points A, B &elevation points.USING SAME SCALE AS MAPgo down to proper elevations,draw plane & measure dip. Source: Donald Wise
BASIC METHOD : RIGHT SECTIONSA sandstone bed strikes N30W and dips 30 Either mentally orSW. Its outcrop width on a flat surface is physically fold the100m. Find its true stratigraphic thickness. paper along this line to make a right sectionIf we could look at a true cross-section drawn below the line.at right angles to the strike, we could measureoff the true thickness (to scale. Below = 1 cm Because this is a right= 100 m). section the full dip of 30’ can be used to drawDraw any random line FF’ at right angles to top and bottom of thestrike. bed in the cross-section. Measure true thickness in right section, normal to bed, using map scale. Source: Donald Wise
RIGHT SECTIONS AT RIGHT PLACESA Coal Bed striking N20E, 50 NW Draw a line through the shaft,crops out as shown. A mine shaft is to perpendicular to strike.be drilled 500 meters due west of theoutcrop. How deep is the coal bed in Make this line FF’ a fold line tothe shaft? draw a right section which will contain the shaft.Select come convenient scale anddraw the map. Draw the dipping coal bed and the shaft in this section. Using the scale, measure the depth of the shaft (550m). Source: Donald Wise
The top and bottom of asandstone crop out atelevations of 600 and 200meters, respectively, at thelocations shown on the map.The strike and dip at bothlocations is N60~E, 20 NW.Calculate the thickness ofthe sandstone. Source: Donald Wise
GREASY DRIP SANDSTONE AREA The Greasy Drip Sandstone is a major reservoir rock in the Petroleum Patch Quadrangle. A small exploration company owned by W.E. Findum and U.R. Lost has hired you to get some data from the outcrop above. What is the strike of the sandstone? _____ What is the dip of the sandstone? _____ to the _____? The thickness of the sandstone is _____? The depth to the top of the sandstone at Grimy Station is _____? What is the vertical thickness of the Greasy Drip SS that would be intersected in a coring made at Grimy Station? _____ Source: Donald Wise
ONE POINT PROBLEMSGiven one point on a map where the strike, dip, and elevation of a planar bedare known, draw the structural contours for this bed throughout the map area.For example, in an area of very sparse exposure, you have only one outcrop ofa coal bed, point A, at an elevation of 1900 feet and strike N60W, 30 SW.Nevertheless, you need to complete a geologic map of the concealed line ofoutcrop of the bed across the area and get the predicted dill depths to the coal.These determinations will require a knowledge of the structural contoursacross the area.
ONE POINT PROBLEMSExtend the line of strike from A to some convenient place off the map. This line is astructural contour and all locations along it are at 1900 foot elevation.Draw a line perpendicular to the structural contour. This will be a right section.The line is at the same elevation as the structural contour (1900 feet). Using thesame scale as the map, put in the elevation lines below the 1900 foot elevation line ofDCE and mark their elevations as shown.This is a right section, so the true 30 degree dip can be plotted starting from point C(which is at 1900 feet elevation).
Find the intersections of the dipping plane in the cross section with theappropriate elevations (F, G, H, I, etc.) and project them up to the surface asL, M, N, O, etc. These are now map points below which the elevations of theplane are known.Structural contours can now be drawn through each of these points parallelto the main 1900 foot contour (AB). The same spacing and trend of contourscan be continued across the entire map. Source: Donald Wise
How deepwould youneed to drilla well atPoint B tointersect thetop of theformationwhichoutcrops atPoint A? Contour Interval = 100 m
Two-Point ProblemsDetermine the Strike and Dip
Three Point ProblemsGiven 3 points on a planar Draw structural contours through thesurface, find the strike & dip high and low points parallel to theof that plane. strike. (AE&CG)Connect the highest and lowest Draw a fold line perpendicular to strike.of the three points on the map. Decide on elevation of this line using(A&C) same scale as map, draw elevation lines below the fold line for cross-section.Interpolate between thesepoints for a point of elevation Project the structural contours of highthe same as that of the and/or low points onto the cross-sectionintermediate elevation point. and draw the dipping plane on this right(B) section.Join these two points of equal *Measure its dip (Angle GEH).elevation as a line of strike.(BD)*Read off this strike withrespect to north Source: Donald Wise
Three Point Problem - Method 2Draw two lines connecting the highest elevation point with both the lowest andintermediate points: (AC; AB).Scale off divisions of equal elevations along each line.Connect points of equal elevations with structural contour lines.Construct right section as in Method 1.
InterpolationA common geologic problem is to be given some numerical value (elevation,for example) at two locations on a map. Intermediate values need to becalculated or INTERPOLATED as proportional distances along the linejoining the two points.THE PROBLEM: Two points A and B are located on a map as shown andhave elevations of 435 and 715 feet respectively. Find a locationproportionally spaced between them which would have a proportionalelevation of 683 feet. While you are at it, find the proportional locations for500, 600, and 700 feet elevations. B 715 A 435Draw the line connecting the two locations, A and B.Source: Donald Wise
InterpolationFrom the end of this line with the lower elevation (point A in this case)draw a random line (AC) at about 30 to 45 degrees from AB.Use some scale of a ruler (in tenths) with values which correspond to theelevation differences between A and B. Put the 4.35 value of the ruler onthe 435 ft elevation of point A and locate point D at the same value as theelevation point B (7.15 for the 715 foot elevation in this case). B 715 A 435 Source: Donald Wise
InterpolationUsing the scale of the ruler mark off on line AD all the locations corresponding to allthe elevations you seek (6.83, 500, 600, 700).Make a large triangle by connecting points D and B. By ruling parallel to line DBmake a series of similar triangles through each of the points you located in the above.A THEOREM OF PLANE GEOMETRY IS THAT DISTANCES WHICH AREPROPORTIONAL TO THE LENGTHS OF LEGS OF ONE SET OF SIMILAR TRIANGLESARE ALSO PROPORTIONAL TO THE OTHER LEGS OF THOSE TRIANGLES.Thus, the locations along line AB havespacing proportional to their elevations.
Outcrop PatternsIf the structural contour on some horizon has the same elevation as thetopography at that point, then that bed crops out at that location.Conversely, if an outcrop occurs at some location, the structural contourof that elevation on that unit passes through that point. Source: Donald Wise
Outcrop PatternsIn general, the outcrop of a dipping plane will “V” in crossing a valley,such that the “V” will point in the direction of dip. With flat dips and steep stream gradients these V’s might point in other direction. If there is no V at all, then the plane is very steep to vertical. This V principal applies to all kinds of planes: beds, dikes, faults, unconformities. Source: Donald Wise
A planar coal bed crops out a points A, B and C. What is the bed’s orientation _______ Draw the outcrop pattern How deep would you need to dig at point D to intersect the coal? __________Source: Donald Wise
Horsefeather Creek AreaStructural Contours on top of Horsefeather Sandstone. Construct a rightsection.What is the orientation of the unit? __________How deep would you drill at P _______ and Q________ to intersect theunit?Draw the outcrop pattern. Source: Donald Wise
Draw section FF’, the axial trace, and fully describe the structure (The numbers represent stratigraphic superposition)Source: Donald Wise
Describe the structure at left. What is the direction of dip of the ss? _______ What is its strike? _________Source: Donald Wise
The St. Valentine Sandstone crops out along ILUVU Creek Valley as shown. Sketch Section A-B.Source: Donald Wise
What kind of fault? Which way does dike A-B dip? Why? Which side went up? Give approximate azimuth and plunge of the net slip and explain how you got it. M, S, T are all faults. Which is the oldest fault? If all the fault movements are dip slip, mark the up and down for those faults where it can be determined.Source: Donald Wise
Guano Creek Field AreaTwo of the more intrepid members of our class, Jon and Dave, have been mapping inthe Guano Creek region, so named for the famed bird rookeries at its headwaters.(The nearly extinct “tweety bird” is rumored to roost in that area.) They are tryingto locate the source of the sulfide ores which oxidize to form a high concentration ofsulfuric acid in Guano Creek, a condition which prompted them to make a boat outof lead to withstand these corrosive waters. Using this field vehicle, they haveproduced the accompanying map but are still up the creek, still in their water craft,still without finding the ores. They need help (in many ways). Should you wish togive a concise one-line description of their condition, please feel free to do so. Inaddition please answer for them:Why is the outcrop width of the Sludge Bucket Sandstone (stippled pattern on the map) three times as wide on the SW side as on the NE side?Describe the Guano Creek fold in as full a detail as possible, including the general orientation of cleavage you might expect associated with it.In as much detail as possible describe Jon’s major fault (including approximate strike, dip direction, approximate motion sense, fault type, relative age).In as much detail as possible describe the Tweety Bird fault (same items as above). Source: Donald Wise
Guano Creek Field Area – SolutionsWhy is the outcrop width of the Sludge Bucket Sandstone (stippledpattern on the map) three times as wide on the SW side as on the NE side? Asymmetric fold – N.E. limb is close to vertical.Describe the Guano Creek fold in as full a detail as possible, including thegeneral orientation of cleavage you might expect associated with it. Asymmetric, N.W. Plunging Anticline.In as much detail as possible describe Jon’s major fault (includingapproximate strike, dip direction, approximate motion sense, fault type,relative age). 080 ° - 90, Right Lateral Transform, younger fault.In as much detail as possible describe the Tweety Bird fault (same itemsas above). 045, Dipping S.E., Reverse, older fault.Source: Donald Wise
Systems of Planar Discontinuities Fold-Related JointsAlthough also the result of tectonic stresses, fold-related joints are shearjoints and occur in distinct patterns of conjugate sets. Source :Twiss & Moores, 2007
Description of Joints –USEPA, Manual of Field ProceduresDescription of Bedding or of Joint or Fracture Spacing: Descriptionshould be according to the following:Spacing Joints Bedding or Foliation< 2 in. Very close Very thin2 in. to 1 ft Close Thin1 ft to 3 ft Moderately close Medium3 ft to 10 ft Wide Thick>10 ft Very wide Very thick(after Deere, 1963)
Description of Joints –USEPA, Manual of Field ProceduresWeathering: Terms used to describe weathering are described below:Descriptive Term Defining CharacteristicsFresh Rock is unstained. May be fractured, but discontinuities are not stained.Slightly Rock is unstained. Discontinuities show some staining on the surfaces of rocks, but discoloration does not penetrate rock mass.Moderate Discontinuity surfaces are stained. Discoloration may extend into rock along discontinuity surfaces.High Individual rock fragments are thoroughly stained and can be crushed with pressure hammer. Discontinuity surfaces are thoroughly stained and may be crumbly.Severe Rock appears to consist of gravel-sized fragments in a “soil” matrix. Individual fragments are thoroughly discolored and can be broken with fingers.
If we divide a circle into ten Contouring Structural Data zones of equal width, the innermost circle will contain 1% of the area. The next circle is twice as large and will contain 4%, but 1% is in the inner circle, so the annulus will contain 3% of the area, and so on. If we stack triangles, each row will contain 1, 3, 5... triangles. A stack ten rows high will contain 100 triangles. If we divide a 60 degree sector of the circle into triangles of equal area, each sector will contain 100 triangles, each with 1% of the area of the sector.From:http://www.uwgb.edu/dutchs/structge/SL133Kalsbeek.HTM
Contouring Structural Data The Kalsbeek counting net is based on this principle. It consists of ten equally spaced circles. Each annulus is divided into triangles. Altogether there are 600 triangles. At each vertex, six triangles meet. The hexagon of triangles around each vertex contains 1% of the area of the net.From:http://www.uwgb.edu/dutchs/structge/SL133Kalsbeek.HTM
Plot the data on an equal Contouring Structural Data area net then transfer the overlay to the counting net. Of course, the two nets must be the same diameter!From:http://www.uwgb.edu/dutchs/structge/SL133Kalsbeek.HTM
Contouring Structural Data At each vertex, count the number of points in the surrounding six triangles and plot the number at the vertex. You may want to do this on a second overlay above the data overlay. Each triangle is common to three hexagons so every point is counted three times. (No, this does not mean the densities have to be divided by three.) Be certain to check every vertex close to the data points to be sure of not missing any. From:http://www.uwgb.edu/dutchs/structge/SL133Kalsbeek.HTM
Contouring Structural Data Remove the numbered overlay and contour the data.From:http://www.uwgb.edu/dutchs/structge/SL133Kalsbeek.HTM
Contouring Structural Data Place the contoured data over a Schmidt Net and rotate it so the highest concentration data is on the E-W diameterFrom:http://www.uwgb.edu/dutchs/structge/SL133Kalsbeek.HTM
Contouring Structural Data Construct a plane 90° from the central cluster of the data and read the dip angle directly off the E-W diameterFrom:http://www.uwgb.edu/dutchs/structge/SL133Kalsbeek.HTM
Contouring Structural Data Rotate the entire overlay back to north and read off the predominant orientation of the joint set.From:http://www.uwgb.edu/dutchs/structge/SL133Kalsbeek.HTM
Using the Structural Data measured earlier, calculate the direction and degreeof anisotropy for the following situation: Joint Set No 1 – 049 60NW Joint Set No. 2 – 336 56 NE Field Hydraulic gradient - 0.05 180° Field Hydraulic Gradient 100 ft
Current ResearchThe simple partitioning of groundwater into intersecting joints iscomplicated by the differential partitioning which occurs betweenupgradient-facing and downgradient-facing intersections Plan View
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