Geologic History Field Investigation - Minnehaha Falls
In this inquiry-based geology field investigation students will investigate sedimentary geology, stream processes and topography in the Minneapolis/St. Paul area at Minnehaha Park and the St Anthony Falls area. Students will document their observations of rock layers, stream processes and land surface features as well as infer past changes in the depositional environment in the area.
At the Minnehaha Falls site, students will make field observations in 3 different primary areas – along the falls themselves, in the "Deer Pen" area (an abandoned stream valley) and along the creek below the falls toward the Mississippi River.
The activity at the St Anthony Falls area will be akin to a geologic and historical walking tour to provide students with a larger geologic context and provide them the opportunity to make inferences and connections to observations made at the Minnehaha Falls site.
Students will practice observation and questioning skills and apply geologic principals such as superposition and uniformitarianism to infer past processes acting in the area and recognize the environments and landscapes change through geologic time.
Students will make predictions about future changes in the landscape based on their observations of current processes.
Students will come to understand that "rocks tell stories" and create their own story of the geologic history of the area based on their own observations. The field investigation will provide students with an experiential context for subsequent classroom geology activities throughout the school year.
The characteristics of rock layers provide clues to the environment in which they formed.
In a sedimentary sequence, older layers are found beneath younger layers.
Waterfalls migrate upstream through time.
Streams have both constructive (deposition) and destructive (erosion) elements.
Erosion, deposition, superposition, sediment
Context for Use
We estimate approximately 2 hours in investigations at Minnehaha Park and approximately 1.5 - 2 hours in the St. Anthony Falls area. Additional time will be allowed for lunch and travel between the sites and the school.
Students will have been given minimal "background" instruction on the geology and processes they will see at the sites. Rather, this activity is envisioned largely as a "discovery" experience with the opportunity for students to practice more open-ended inquiry based on what they observe, with prompting from the instructors to make logical connections between what they see in the field and what they have seen elsewhere in their own experiences. Time for follow up discussions will be provided during subsequent class periods.
No specialized equipment is required other than magnifying lenses, which will be helpful in examining rock grains along Minnehaha creek. Students will need paper or notebooks for recording observations and sketches.
Resource Type: Activities:Field Activity
Special Interest: Field-Based Teaching and Learning
Grade Level: Middle (6-8)
Description and Teaching Materials
To support the inquiry nature of the student investigation, little "explanation" of what the students will see will be given beforehand to avoid poisoning their logical creativity with thinking they are supposed to find "the one right answer" that the teacher already has hidden in his/her pocket. Instead, the students will be given the charge that "We're trying to see if we can make observations that lead us discovering the story of how what we see here came to be." They will be instructed to have their journal chock full of observations, labeled sketches, and questions and wonderings by the end of the day. The students will have to draw on their own existing knowledge of the world and bounce ideas around with each other to defend their own conclusions.
This activity will require multiple chaperones drawn from parent volunteers, other teachers and potentially geology students at local universities. The chaperones will be given an orientation to questioning strategies to prompt the students and keep them heading in a productive direction. Informal questioning, discussion and interaction between the chaperones and the students is an essential component of this Field investigation. In addition, the guides will be provided with some specific items to point the students attention to.
Students will be recording observations/descriptions and sketching in their journals, with a section for each of the substations.
AT MINNEHAHA PARK
Students work with a partner and are divided into 6 groups of approx 24 students with a minimum of 2 adult chaperones per group. Two groups will be operating simultaneously along different parts of each "station" (The Falls, The Deer Pen (abandoned river channel), Minnehaha Creek walk), with 30 to 35 minutes per station and each group cycling through each station.
General prompting questions for the stations will be provided to and modeled for the chaperones and include the following; –
What do you notice?
What do you think it means?
What does that suggest to you?
How many layers do you see? Describe them to me.
What do you think happened here?
What would you look for then?
What evidence do you have for that?
What would you see and what wouldn't you see then?
What do you see happening now?
Starting at the bridge over top of the Falls students will make observations about what they see and then walk down the sidewalk at the side of the falls making and recording observations along the way. Near the bottom of the falls, the students will make a detailed sketch of the falls and the rock layers they see.
In addition students will write a list of at least 12 things they observed or noticed about the stream and rocks in the falls area.
The Deer Pen (abandoned river channel)-
Students will have an opportunity to look around the large open area then come up with ideas for "What Happened Here?" Led by the guides/chaperones, the students will suggest and defend their ideas to each other, then each pair will write a short story in their journal of "how the area they're sitting in came to be" and what they would look for as evidence to support their story.
Minnehaha Creek Walk-
After a brief look at Minnehaha Creek valley near the base of the falls, students will walk down the creek toward the Mississippi River. Where safe to do so, the students will be encouraged to put their noses on the rock of the valley wall (St. Peter Sandstone) to see what it's made of (magnifying lenses will help).
Students will also make a list of observations and sketches of everything they notice in the creek bed itself (grain size, rock appearances, erosion, deposition).
Describe and sketch what they see in "the innards" of the rock in the valley walls. What do the rock grains suggest to you about how/where it formed? Where do you think the sand came from?
What do you notice about size of the valley the creek flows in in this area compared to the area near the falls?
St ANTHONY FALLS area
The 150 students will be divided into 6 smaller groups, each led by 2 chaperones/guides. This site will be largely a guided walking tour of the area including the Stone Arch Bridge and board walk on the left bank, The Lock and Dam, and the area just upstream from the hydrology lab.
The area is rife with existing explanatory signage to lead the students through the geologic, milling and engineering history of the area. The students will be given a series of guiding questions to answer based on the information on the signage.
In addition, students will record observations about what they see in the falls area and the rocks exposed in the riverbanks and how they think it might relate to what they see at Minnehaha Park.
After the field trip 2-3 days of class time will be devoted for student processing of the Field trip.
To foster reflection upon the field experience students will create a 3-columned table with the headings "I Noticed (or liked)" – "I learned" – "I still wonder...." The students will fill in one row of the table themselves then circulate to 3 to 5 other students to get other perspectives. A teacher facilitated class discussion about what's in their table will follow.
Rock samples from the 3 primary rock layers at Minnehaha Falls will be available for students to inspect in the classroom and the students will inspect their characteristics. The teacher will also provide some instruction regarding the depositional environments in which these rock types typically form.
As a work product, students will then create their own illustrated story of what they think the geologic history of Minnehaha Park is.
"Pretend you have a time machine and can go back and visit the area you saw on the Field Investigation. Create and illustrate a story of what you would have seen happening through time to result in what you observed at Minnehaha Park and St Anthony Falls today. Base your story on the evidence you observed. Start your story with the oldest event (the sandstone at the base of Minnehaha Falls), work forward in time to today and also predict what the falls will do into the future."
Teaching Notes and Tips
Consideration should also be given to coaching the students to wear appropriate clothing and sturdy footwear and to bring drinking water. Permission slips and contingency plans for weather are essential.
Lead teachers must scout the sites themselves before taking students. It is recommended that the Earth Science instructors do not lead groups of students themselves, but rather be available to rove between groups to facilitate the work of the other guides/chaperons.
It is advisable to contact Minnehaha Park ahead of time to let them know you are coming and check the availability of the shelter for lunch. The trip to Minnehaha could be done by itself in a half school day to simplify logistics.
- informal assessments of students during the field investigation
- examination of observations recorded in the students journals
- review of the students geologic history stories
18.104.22.168 Landforms are the result of the combination of constructive and destructive processes.
22.214.171.124 Rocks and rock formations indicate evidence of the materials and conditions that produced them.