Investigating the Minnesota River's Glacial History Near Henderson, MN.
Initial Publication Date: August 3, 2009
Summary
While visiting three separate sites in or near the Minnesota River valley, students will question the deposition environment of rock types found and the creation of the valley itself. Students will discover find types of rock found far from their point of origin in Minnesota and the region. Students will also determine that the river does indeed flood periodically, but will be left with an enduring question – Are the periodic floods of the Minnesota River the cause of the formation of the valley seen?
Collapse
Learning Goals
The field investigation is designed for students to increase their observation skills and to describe how those observations 'fit' with the general geology of Minnesota. Skills further developed from this investigation include observation, questioning, use of prior knowledge, group communication, writing as well as critical thinking and model development. Rock identification and Minnesota origin will be reviewed throughout the investigation. Mass transport of materials throughout the state will be discovered as students find 'non-native' rocks in a particular location. Vocabulary words to be learned or reviewed by students include: erosion, deposition, glacier, till.
Context for Use
This field investigation is designed for three sections of 8th grade Earth Science (around 70 total students). The field investigation will potentially take the majority of the student school day, though the possibility exists of returning for their fourth block classes. Travel time to the site(s) will be approximately two hours round trip, with three to four hours being planned for the sites visited.
The field investigation takes place after students have had practice with rock/mineral observation and identification. As part of our rock unit, students have become familiar with different types of bedrock that are found throughout Minnesota – examples include igneous rocks of the Lake Superior region, sedimentary of Southeastern Minnesota and the granites found near St. Cloud.
The field investigation also takes place before two units that are covered in our curriculum and will give students an introduction experience to draw from later. One unit covers water systems (lakes, rivers & streams) and particularly the major Minnesota rivers systems that include the Minnesota River. The other unit focuses on weathering and erosion, with specific attention to the glacial history of Minnesota.
The field investigation takes place after students have had practice with rock/mineral observation and identification. As part of our rock unit, students have become familiar with different types of bedrock that are found throughout Minnesota – examples include igneous rocks of the Lake Superior region, sedimentary of Southeastern Minnesota and the granites found near St. Cloud.
The field investigation also takes place before two units that are covered in our curriculum and will give students an introduction experience to draw from later. One unit covers water systems (lakes, rivers & streams) and particularly the major Minnesota rivers systems that include the Minnesota River. The other unit focuses on weathering and erosion, with specific attention to the glacial history of Minnesota.
Description and Teaching Materials
This field investigation is comprised of three separate stops that will generate student questions about what they are seeing so that we can elaborate later in the investigation or in the classroom. All students use an 'Investigative Journal' in the classroom for labs and other activities, it is expected that their journals will accompany them on the field investigation.
Our first stop on the investigation will be at a position where students can see the layout of the Minnesota River valley. It may be at the top of a bluff or inside the valley (I need to scout potential spots that fit with our direction of travel), the idea is that students should be able to gauge the width and depth of the valley, position of the river and other general topographical features. In their journals, students will draw a profile of what they see, including estimates of the width and depth of the valley. A question that should be considered at this stop is 'How did what you are seeing form?'
The second stop on the investigation takes place at a dike gate in the city of Henderson within the Minnesota River valley. Here students will notice a dike that completely encircles Henderson and generate questions as to the dike's function. Students will be asked again to draw a profile at this location – including the depth and width of the valley, the river, the dike, and the city of Henderson.
Our third and final stop on the investigation is a short drive (2.7 miles) from Henderson and is at the Rush River County Park. At the Rush River students will examine two features – a cut bank face and a rocky point bar. Students will break into cross-gender teams and gather at one of the two rocky point bars. At the point bar, student teams will begin to identify the different types of rocks that make up that location and collect samples to bring back to the classroom for further study. Here they will find different basalt, rhyolite and other igneous rock types, as well as some shale and other sedimentary rocks. Because students are already familiar with locations within Minnesota that different rock types are found, they should begin to ask why these igneous rocks from the Lake Superior region are found so far south. While identifying different rock types, students may need a dilute solution of hydrochloric acid to aid in the process. Once finished at the point bar, students will turn their focus to the cut bank immediately across the river. In their Investigative Journals, students will sketch the cut bank (it is made up of several very distinctive glacial tills readily seen by the naked eye) focusing on the layout of the different colors. If the river is at a sufficiently low stage, students will cross the river to gather samples of the different regions of the cut bank. Samples that the students will want to bring back across the river include different rock samples from the different layers as well as the 'dirt' portion, the glacial till. The samples collected will also be used in the classroom during an 'Investigating Minnesota's Glacial Tills' lab activity that is completed a few weeks after the investigation.
This entire investigation is based on allowing the students to begin to grasp the 'big picture' of Minnesota's glacial history. They will see clues to this history, begin to question the clues and discuss these clues with other students. When looking at the Minnesota River Valley some students will immediately infer that the river itself carved the valley, while others will argue that the valley is too big to be carved by the Minnesota River. Our stop at Henderson to view the dikes will embolden the argument that the river carved the valley since the city must be subjected to floods even though it is located on the far edge of the valley floor. Common questions from our stop at the Rush River will dwell on processes that occurred to move these different rock types all across Minnesota and beyond. Was it wind? Water? People? All of these questions should be formed, recorded in student journals and will be discussed later in the classroom.
Our first stop on the investigation will be at a position where students can see the layout of the Minnesota River valley. It may be at the top of a bluff or inside the valley (I need to scout potential spots that fit with our direction of travel), the idea is that students should be able to gauge the width and depth of the valley, position of the river and other general topographical features. In their journals, students will draw a profile of what they see, including estimates of the width and depth of the valley. A question that should be considered at this stop is 'How did what you are seeing form?'
The second stop on the investigation takes place at a dike gate in the city of Henderson within the Minnesota River valley. Here students will notice a dike that completely encircles Henderson and generate questions as to the dike's function. Students will be asked again to draw a profile at this location – including the depth and width of the valley, the river, the dike, and the city of Henderson.
Our third and final stop on the investigation is a short drive (2.7 miles) from Henderson and is at the Rush River County Park. At the Rush River students will examine two features – a cut bank face and a rocky point bar. Students will break into cross-gender teams and gather at one of the two rocky point bars. At the point bar, student teams will begin to identify the different types of rocks that make up that location and collect samples to bring back to the classroom for further study. Here they will find different basalt, rhyolite and other igneous rock types, as well as some shale and other sedimentary rocks. Because students are already familiar with locations within Minnesota that different rock types are found, they should begin to ask why these igneous rocks from the Lake Superior region are found so far south. While identifying different rock types, students may need a dilute solution of hydrochloric acid to aid in the process. Once finished at the point bar, students will turn their focus to the cut bank immediately across the river. In their Investigative Journals, students will sketch the cut bank (it is made up of several very distinctive glacial tills readily seen by the naked eye) focusing on the layout of the different colors. If the river is at a sufficiently low stage, students will cross the river to gather samples of the different regions of the cut bank. Samples that the students will want to bring back across the river include different rock samples from the different layers as well as the 'dirt' portion, the glacial till. The samples collected will also be used in the classroom during an 'Investigating Minnesota's Glacial Tills' lab activity that is completed a few weeks after the investigation.
This entire investigation is based on allowing the students to begin to grasp the 'big picture' of Minnesota's glacial history. They will see clues to this history, begin to question the clues and discuss these clues with other students. When looking at the Minnesota River Valley some students will immediately infer that the river itself carved the valley, while others will argue that the valley is too big to be carved by the Minnesota River. Our stop at Henderson to view the dikes will embolden the argument that the river carved the valley since the city must be subjected to floods even though it is located on the far edge of the valley floor. Common questions from our stop at the Rush River will dwell on processes that occurred to move these different rock types all across Minnesota and beyond. Was it wind? Water? People? All of these questions should be formed, recorded in student journals and will be discussed later in the classroom.
Teaching Notes and Tips
Having not completed this field investigation yet, I must speculate on concerns that I have at this time. One stop may require students to cross a river to make detailed observations - though water levels should probably be low in the fall, water temperatures will be low as well. Lifejackets may be required for students to cross the river and potentially wading boots, a change of clothing will probably be a necessity. Parent volunteers will also be necessary, and the volunteers will have to understand that they will be 'active' volunteers. This investigation will be different for both my students and I because we have generally interpreted the geology of Minnesota from the classroom, not from the field.
Share your modifications and improvements to this activity through the Community Contribution Tool »
Assessment
Assessment of how students are learning or learned the goals of the activity focuses on two periods – during the investigation and after the investigation. During the investigation it will be critical talk to the different groups/teams of students and ask open-ended questions about their observations. After the investigation, assessment will be determined based on reading of their investigation journals that all students utilize. The journals will have student observations, questions, drawings, etc. of each site, as well as a 'I noticed..., I learned...., I still wonder....' exercise that will be completed upon return to school.
Standards
8.3.1.2.2 – glacial activity