Mod 10 PT 2 ASSIGNMENT

Kendall Hunt publishing company7 Source: Alexandra Price Geologic Maps Geologic maps represent the distribution of rock types on the surface of the Earth as well as geologic features like faults and folds using a topographic map as a base. These maps are a primary source of information for a geoscientist by depicting various rock units using different colors. These maps can be used to assess ground-water quality, contamination risk, landslide hazards, mineral resource potential, and land-use planning among other uses. Each feature on a geologic map has a has a unique symbol and each rock unit has a specific label and color. Geologic Cross Section A geologic cross section is constructed using the surface expressions of rock layers to predict their structures in the subsurface of the Earth. The cross section represents a plane perpendicular to horizontal surface and is drawn from one point to another. Each end of a cross section is generally labeled A to A’ and corresponds to surface locations on a geologic map. If more than one cross section is depicted for a map, the additional sections might be labeled B to B C to C’, etc. The depth of the rock units from surface (y-axis) MUST be exaggerated in order to be visible at this scale. This is called vertical exaggeration and generally ranges from 1:20 or more and is reported with the cross section. Figure 2: Example cross section drawn from a geologic map showing tilted beds, folds, and an unconformity. 7

Part Three: Making a Topographic Cross Section (10 pts) Topographic cross sections are much like geologic cross sections, but they allow a map reader to see a surface profile view of the elevation from one point on a map to another. In this part of the lab assignment we will make a cross section of the topographic map you just contoured. To do this follow the steps below: « Find the two highest elevation points on the map you created in Part 2. These points will be A = 106 ft and A’ = 103 ft. * Place a sheet of graph paper above your contour map (See the layout in Figure 3 below). It helps to fold your graph paper along one of the horizontal lines of the grid. Use a line toward the bottom half of the paper so that you have enough room to create your section. ¢ Label each endpoint A and A” on your graph paper. « Place a tick or hatch mark on each topographic contour through your cross section and note the elevation. « Unfold your paper and create a graph using the height of each dot made on the map. « Connect the dots to create your profile of the elevations depicted on your contour map. Figure 3: Example of how to lay your graph paper on your contour map to create your topographic profile cross section. Part Four: Geologic Map and Cross Section (20 pts) * Color the map below with the colors from the legend below as close as possible to your set of pencils. 3pts Axial Plane (- Strike 5/ Anticline 3~ & dip Axial Plane ault /\mlmc 7 After answer/complete the following questions:

« What type of fault is this? Normal, reverse, or thrust? 1pt o Label the direction the fault blocks movement of the fault in the northwest corner of the map which trends east/west. You should have two arrows. This movement map be less apparent. Use an educated guess anyways. 1pt e What is the youngest surface unit on the geologic map? 1pt What is the oldest unit on the geologic map? 1pt What is the geologic structure which goes across the map trending southwest to northeast? 1pt What is the geologic feature in the lower right comer of the map? 1pt What type or rock types make up Jurassic age rocks in this geologic map? 1pt What is the (average) dip on the beds near A’? 1pt What is the maximum dip bedrock can measure in the field? 2pts 1

Which cross section is this? A to A’ or B to B'? 1pt 9 . | 9” Cross Section ?-7' Describe the likely lithology of the youngest unit on tl’_]e geologic map based on all of your geologic knowledge from this course. 2 pts Describe the likely lithology of the oldest unit on the geologic map based on all of your geologic knowledge from this course. 2 pts 12