Stop 1 | Stop 2 | Stop 3 | Stop 4 | Stop 5 | Stop 6 | Stop 7
This road log lists all the learning goals and questions posed at each stop. Also listed are additional resources that may be of use when addressing the questions.
Stop 1: Gallatin River
- Geology influencing location of groundwater
- Aquifer properties
- Critical evaluation of data
- Find yourself on the map. Using the geologic maps , determine which rock unit the Gallatin River is flowing over?
- Sketch a topographic profile of A-A'. Draw in the rock units.
- What are the gravel units above the Gallatin River?
- How are they related to the cut and fill events?
- Look at the vegetation on the banks and bars, does the Gallatin River seem to be actively depositing sediment? How does the vegetation help you determine this?
- From your earlier observations, do you believe the Gallatin River is actively depositing the West Gallatin Alluvium?
- Using the USGS Stream flow data , can you support your hypothesis regarding whether or not the Gallatin River is actively depositing the West Gallatin Alluvium?
- Sketch the river. Make a note of the location of specific grain sizes and what controls the location of grain size across the river.
- If an alluvial aquifer was deposited in such a manner, would you expect ground water to move through it in a uniform fashion?
- How will the distribution of grain size effect groundwater transport in the future?
Stop 2: Hard Rock Quarry
- Geology influencing location of ground water
- Evolution of valley
- Ground water flow aquifer properties
- Spatial reasoning
- Sketch the outcrop. Include a scale, thickness and any other relevant information to describe the outcrop.
- Click on the photo of the outcrop and assess the rock. Click the second photo to see a thin section of this type of rock. Note the mineral type, porosity, and other relevant information to describe the rock.
- How well do you think water flows through this rock? What does the Aquifer/Aquitard map tell us about groundwater transport through this rock?
- Compare and contrast the vegetation covering the West Gallatin Alluvium and the Gneiss.
- What might this mean about the water holding capacity of the rock units?
- Would you expect a well drilled into the gneiss to yield any water? If so how much?
- What kind of rock do you expect to see on the benches to the south?
- Build a hypothesis that might explain this phenomenon of oscillating topographic elevation of the top of gneiss. What kind of data would you want to support your hypothesis?
Stop 3: Tertiary Sediments
- Understand how geology influences groundwater
- Learn about the geologic evolution of Gallatin Valley
- Spatial reasoning
- Find yourself on the geologic map. What rock unit are you looking at?
- Write a geologic description of the rock unit. Be sure to include grain size, grain shape and a sketch of the rock unit.
- Is this rock unit an aquifer or an aquitard? If it is an aquifer, is it the best aquifer in the area?
- magine you are standing on this very spot in the Tertiary age (about 70 million years) Remember in Stop 1 we saw the river depositing a gravel unit with areas of silt and sand. Describe the depositional environment.
- Are you feet wet?
- If so, are you treading water or just standing in water?
- Are you near a river, lake, ocean?
- What else might you see in the area?
- How much energy is in the system?
Stop 4: Unconformity
- Develop some map interpretation skills
- Begin to understand the big picture geology of the area.
- Spatial Reasoning
- Look at the well data. Does this give you an idea of what the gneiss might look like in the subsurface? Draw a sketch of subsurface profile of the crystalline rock.
Stop 5: Day Ranch Overview
- Develop the idea of geology influencing groundwater location and how that relates to the history of Gallatin Valley.
- Begin to understand the complexity of the issue and how geology and policy relate.
- Start to evaluate how we use data in this argument and begin to understand how to evaluate that data.
- What kind of rock is found at the Day Ranch site?
- How thick do you think this rock unit might be? How far below is the gneiss?
- If you were a geologist for the consulting company hired to determine the water potential at Day Ranch, what questions might you be asking yourself? Would you be concerned about the groundwater potential for the Day Ranch bench?
- Looking again at the well data, how deep of a well do you think you would have to drill to get enough water up on the benches?
- Using your Topographic Maps and Surficial Geology maps, determine what rock unit the Day Ranch owns on the valley floor.
- Map interpretation:
- Using the other maps provided, assess this rock unit for water bearing capacity.
- Is it an aquifer or aquitard?
- What is the transmissivity?
- Is it a "better" aquifer than the Tertiary sediments found on the bench?
- Using the well data and the geologic maps, compare and contrast the aquifer on the valley floor and the aquifer on the bench. Which aquifer would you, as a consulting geologist, suggest the Day Ranch use?
Stop 6: Fish Creek
- Continue to learn how to use scientific data.
- Learn how stream flow is measured.
- Look at the USGS daily stream flow values for the Gallatin River.
- Are there daily fluctuations?
- Notice the median daily stream flow based on 73 years of data.
- How do the daily measurement fluctuations compare to overall trend in stream flow for the river?
- Look at the Fish Creek stream flow values.
- Compared to the years of data provided on the USGS site, are there enough measurements to draw conclusions in terms of changes in stream flow?
- Does your measurement fit on the curve established between February and December 2001 and the 2002 irrigation series curve?
- If you were to pump 83 gallons per minute (the average demand for the golf course identified by Day Ranch developers) from a well at location DR, how would that impact Fish Creek (give a numerical answer).
- Would you use this data in your argument? What other data would you like to have?