1. Geologic Structures in Block Diagrams and Cross-Sections
2. Geologic Map of Washington State
3. Virtual Field Sites

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I. Geologic Structures in Block Diagrams and Cross-Sections

In performing this lab, you will be expected to remember the geologic structure information you read about on the Basics Web page on geologic structures, including the Table of Geologic Folds and the Table of Geologic Faults.

Print out block diagrams 1-6. You will be printing two pages. One page contains blocks 1 through 4. The other page contains blocks 5 and 6.

Perform the following:

• On each and every block diagram:
  • Number the geologic layers in relative geologic age sequence.
    The relative geologic age sequence goes from 1 (oldest layer) up to highest number (youngest layer).
  • Put the number in the layer on every place in the block diagram where the layer appears. For example if the oldest layer appears once on the front of the block diagram, once on the side and in two places on the top, label it with the number 1 in all four locations.
    
• For block diagrams 3 and 4:
  Name the type of fold.
  (Write the names down underneath the block diagrams.)
  
• For block diagrams 3 and 4:
  Draw the appropriate fold symbol along the axis (down the center) of the fold.
  • The fold axis symbol should ONLY be drawn on the map side of the block diagram. The map side is the top side.
  • Refer to the Table of Geologic Folds for fold axis symbols.
    
• For block diagrams 5 and 6:
  Name the type of fault.
  (Write the names down beneath the block diagrams.)
  
• For block diagrams 5 and 6:
  Draw a half-arrow on each side of the fault, showing which way the rocks were offset.

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II. Geologic Map of Washington State

Use a geologic map of Washington State that came with your rock kit.

(If your rock kit is missing a geologic map, you can print the geologic map of Washington State at https://commons.wvc.edu/rdawes/G101OCL/Labs/ger_geol_map_washington_pagesize.pdf )

• It requires Acrobat Reader to open the map online.
• The map may appear small and difficult to read.
• You can zoom in on the .pdf version of the map on your computer screen by clicking on the magnifying glass icon and then clicking on the map.)
• You can keep it on your computer screen for reference when marking on the printed version.)

On your printed map, use colored pens to:

• Draw circles carefully around each of the following geologic structures.
• Draw numbered arrows pointing to each of the geologic structures that you have circled.

1. Thrust faults and thrust sheets of the Olympic Mountains. (Remember that thrust faults are thick black lines with triangular "teeth" on them. The triangles are on the side of the hanging wall.)
2. Thrust faults and thrust sheets of the San Juan Islands.
3. Thrust faults and thrust sheets of the western North Cascades (near Mt. Baker).
4. The Straight Creek Fault. Like all the faults, the Straight Creek Fault is shown as a thick, black line. Look closely in the North Cascades area for half-arrows alongside the fault, showing strike-slip offset directions. The Straight Creek Fault separates blue-violet colors of the North Cascades Crystalline Core (metamorphic rock) from brown and green colors of the western Cascades (sedimentary and older volcanic rock).
5. The Methow "Graben," which extends to the British Columbia border, just east of the North Cascades, has faults on either side (thick black lines) and is filled mainly with green color representing Mesozoic sedimentary rock.
6. The Chiwaukum Graben (or Chiwaukum "pull-apart basin"). Look closely. Wenatchee is in the graben, near the southeastern end of the graben. The Graben has faults on three sides and is mainly filled with light green color representing Lower Tertiary sedimentary rock.
7. Anticlines and thrust faults of the Yakima Fold Belt. The anticline fold axis symbols are red. The thrust faults are thick black lines in the same area as the folds and approximately parallel to the fold axes. Circle this whole area as well as draw an arrow numbered 7 that points to it.
8. The Republic Graben. It is in northeastern Washington. It shows up as a strip of brown color, which shows that it is filled mostly with Lower Tertiary volcanic rock. There is a major fault (thick black line) on each side of the graben.
9. The Okanogan Metamorphic Core Complex (or Okanogan "gneiss dome"). The Okanogan complex is adjacent to and west of the Republic Graben. It is the pink and gray color area that runs west of the Republic Graben to the Okanogan detachment fault. The Okanogan detachment fault is a thick black fault line that has black rectangles. It runs in a north-south direction along the Okanogan River.
10. The Kettle Metamorphic Core Complex (or Kettle "gneiss dome"). The Kettle complex is east of the Republic Graben. It is the area of pink and gray color that runs east from the Republic Graben to the Kettle detachment fault. The Kettle detachment fault is a thick black fault line that has black rectangles.
    

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III. Virtual Field Sites

Explore the Priest Rapids Virtual Field Site and answer the following questions.

1. Name the type of fold that forms the crest of the Saddle Mountains.
2. Name the type of fault that marks the northern edge of the Saddle Mountains.
3. What is the name of the formation that shows up as a white layer between the basalt flows in the Saddle Mountains? (An example of the name of a formation is the "Blakeley Formation."
4. What type of rock or other geological material is IN the formation of the previous questions, which provides evidence that volcanic activity of the Cascade Mountains overlapped in time with eruptions of the Columbia River basalt flows? (A two-word answer would be sufficient, the first word specifying the igneous composition, the second word specifying the type of volcanic material.)
5. In igneous rocks, what is the name of the holes that form from gas bubbling out of a lava flow? (One word.)

Explore the Sun River Virtual Field Site and answer the following questions.

6. What type of fault dominates the geologic structure at Sun River, Montana?
7. What type of stress was the crust subjected to when those faults formed?
8. In the French Gulch thrust, what type of rock is in the footwall? (One word.)
9. In the Sawtooth thrust, what type of rock is in the footwall? (One word.)
10. Both Sun River and the Yakima Fold Belt (see the Priest Rapids Virtual Field Site) have thrust faults and folds that developed from the same type of stress. What difference between Sun River and the Yakima Fold provides the clearest evidence that the two areas were not formed by the same source of stress in the crust? (Choose one.) Different orientation of the thrust faults and fold axes. Different types of rocks. Different geologic age. Different location.

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