LABORATORY 1

These are some of the terms we will learn in class.  It is very important that you become comfortable with them.  We will use them in class, in the field, and you will see them again on the exam.



STRIKE:
definition- The compass direction of a horizontal line on an inclined plane.
explanation- The strike measures the orientation (bearing, direction) of a planar feature.  It is the intersection (a line) of the planar feature with an imaginary horizontal plane.  The strike is measured in that horizontal plane.

DIP:
definition- The angle of inclination of a planar feature measured from a horizontal datum.
explanation- The dip measures the angle (inclination) of a planar feature.  The dip is measured in a vertical plane that is oriented perpendicular (orthogonal, 90*) to the strike direction.  The dip will not be a value greater than 90*.

TREND:
definition- The azimuth of a linear geologic feature, commonly of a fold axis, and written as a compass bearing.
explanation- The trend measures the orientation of a linear feature.  The trend is measured in the down plunge direction of the line in the horizontal plane.

PLUNGE:
definition- The angle between a line and the horizontal datum plane.
explanation- The plunge measures the angle of a linear feature.  The plunge is measured in the trending direction in a vertical plane with respect to the horizontal datum.

QUADRANT NOTATION:
Divided into four 90* quads, NW, NE, SW, SE.  The bearing is read from north or south with deviation to the east or west.  It is an older system, used by most, and has some internal checks.  Must be translated to azimuthal for most computer applications.

AZIMUTHAL NOTATION:
0 -360 degrees, all bearings are read from north.

RIGHT-HAND-RULE:
The RHR is a form of azimuthal strike and dip notation.  It is necessary when working with some computer programs.  The RHR measures the direction of the strike with the dip of the plane always to the right of the measurer.

PITCH (RAKE):
The angle between a lineation (linear feature) and the strike of the surface on which it occurs.

DECLINATION:
The angle between magnetic north and true (geographic) north.  The declination can be dialed into your Brunton

CLINOMETER:
An instrument for measuring the angle between an inclined surface and the horizontal datum.  The clinometer is used to measure the dip of a bedding plane, a cleavage plane, a fault plane, etc.; and the plunge of a lineation, a fold axis, a ripple crest, etc.
 


Helpful Hints for completing lab #1.

Part One.

Just stick with it.  Try to think in 3-dimensions and draw sketches.

Part Two.

2.1 Try drawing the orientation in the circle first.  Then you can check yourself during the translation.  Remember, no RHR for lines.

2.2 Again, try to draw the orientations of each.  Canít have a NW striking plane that dips to the NW, right? How about to the SE? Nope, canít have that either.  This is one of those checks inherent to the quadrant notation.  Your strike and dip can never be in the same quadrant.  They can also never be in opposite quadrants (i.e., SW and NE, NW and SE).

Part Three.

3.1 You can measure the ground distance, the ground slope, and you know the dip of the bed.  Now construct triangles until you find the one that helps.

3.2 Remember where your datum is, above or below you.  Dip is always perpendicular to strike.

Come see me about any problems you are encountering.  I am happy to help.