Field Activity: Exploring Glaciers, Ancient Seas, and Volcanism

Goal A: Students will recognize that volcanic activity can be caused by the formation of a rift valley, resulting in layers of successive lava flows.
Objective A-1: Students will identify at least 2 separate lava flows at Interstate State Park and verbally explain how to identify flow boundaries with 90% accuracy as measured by a teacher check-off list.
Objective A-2: Given an essay question following the field study, students will explain how a rift valley forms and why the Dresser flows at Interstate State Park can be identified as an ancient rift valley. Students will receive a score of 3 or 4 on a 4 point rubric.
Goal B: Students will observe and recognize glacial features, such as potholes, glacial polish and striations, and an ancient glacial river valley.
Objective B-1: Students will observe, measure, and record data on 5 potholes at Interstate State Park. Utilizing information from a prior inquiry-based activity, students will postulate the mechanisms of pothole formation and verbally state it to a group leader.
Objective B-2: Students will investigate and gather evidence to prove the case for glacial activity in the Taylors Falls area, which will be documented in a written summary following the field study. This will receive a score of 3 or 4 on a 4 point rubric.
Goal C: Students will observe that different rocks weather and erode at different rates, causing physical features, such as waterfalls, to form.
Objective C-1: In cooperative small groups using inquiry-based learning, students will observe the differing erosional rates of the Franconia formation, which has resulted in the formation of a waterfall. Students will report their findings in a field study guide using diagrams and complete sentences.
Objective C-2: Students will make observations and deduce that sandstone overlied basalt at Interstate State Park and predict which unit erodes more easily. These predictions will be utilized in a follow-up summary lab following the field activity, where students will receive 80% or better on a 5 question quiz.
Concept #1: Landforms are the result of the constructive and destructive processes.
Concept #2: Rock formations indicate evidence of the materials and conditions that produced them.
KEY VOCABULARY:
basalt, vesicles, vesicular basalt, conglomerate, sandstone, crossbedding, viscosity

This all day field investigation is designed for 8th grade students who are in small groups of 15 with a group leader. Although these students have been exposed to basic geology concepts prior to this field activity, it would not be a necessity. Two inquiry activities, however, would be recommended prior to this field activity. The first is " Air bubbles in Viscous Liquids", and the second is "Sanding Rocks". Both these lab activities are posted within this activity. While these activities could be included in any curriculum, the field activity is unique to Interstate State Park and the Taylors Falls area.

In this field study, 8th grade students study three separate geological formations in Insterstate State Park: the first is an ancient rift valley made up of consecutive lava flows, the second is the remains of an ancient sea floor, and the third studies glacial feaures, such as poholes within a glacial meltwater river valley.
Prior activities include an inquiry activity studying bubbles in a thick liquid, (Viscous Liquids), and an inquiry activity where students sand rocks and estimate how long it would take to make a square rock "round" (Sanding Rocks).

Students also receive guidelines for the day's activities in the classroom before departing. Students will bring a notebook, a set of questions, a topographic map of the area, and an itinerary for their group. This trip is divided into 6 separate investigations and activities:

Investigation #1:In the first phase of the field trip, students will study lava flows in the park, with particular attention to vesicles (bubbles) at the top of each lava flow. Student groups will identify at least 2 separate lava flows and explain how they are able to find these boundaries. (Note: students will find the top of one lava flow just south of the visitor center, and walk down the tar road to the stairway where the top of the next lava flow can be located within a large pothole.Following this activity, students will hypothesize what could have caused such large lava flows. Through inquiry questioning and reasoning, the lava flows will be constructed as a rift valley. As a follow-up to the field activity, students will draw a cross section of the rock units, placing the lava flow at the base, and then place this event in a written timeline.

Investigation #2: Students will tour the pothole trail and examine the potholes created during glacial times. Students will be encouraged to take note of the vesicles in the basalts and the minerals that fill them. Students might also be encouraged to notice where large blocks of basalt have dropped, as evidenced by the vesicle layers, and also cracking and faulting that can be seen in the basalt.

Investigation #3: Students will tour the "baby potholes" along the trail while on a short walk to the bridge crossing the St. Croix River. There, the students will ponder the uses of this river by the early European pioneers for logging, transportation, and power. The discussion of the town's name, "Taylor's Falls", will be discussed. Students will be encouraged to consider what happened to the "falls".

Investigation #4: Following the study of the lava flows, potholes, and bridge, students will be board buses where they will exit to examine the conglomerate of basalt boulders in a sandstone matrix near the "Welcome to MN" sign south of the visitor center on Hwy. 8. The will identify the boulders as basalt similar to the lava flows they just witnessed, and deduce that the boulders must have fallen into the sand, i.e. the basalt was in existence prior to the sandstone.

Investigation #5: Following the study of the conglomerate, students will hike from the MN side campground/boat landing to the Curtain Falls Overlook on the Sandstone Bluffs Trail, where they will observe and hypothesize about the origin of the rock unit (sandstone) and the origin of the waterfall. Students will draw diagrams and take field notes on the waterfall and rock unit. They will: 1) predict which parts of the sandstone unit erodes most easily, 2) predict which might be older, the basalt or the sandstone, and 3) predict which might erode more easily, the basalt or the sandstone, and 4) hypothesize why. After completing the field activity, students will continue to construct a timeline and draw a cross section of the Taylors Falls area.

Investigation #6:The final exercise in this field activity (following lunch), includes an analysis of glacial features found in Interstate State Park. After viewing the 20 minute video about glacial features in Wisconsin at the visitor's center on the Wisconsin side. Students will walk on the pothole trail on the Wisconsin side to make observations and collect data through observation of the potholes in the park. They will verbally hypothesize as to how the potholes might have been formed utilizing the inquiry activity on erosion referred to in this description, and also why the potholes on the Wisconsin side are not as large as those on the Minnesota side.

This was a great kick-off to our geology unit! The students really got to see rock units "up close and personal", and they were very positive about the experience. When we covered rock types shortly after the trip, they understood that rock samples represented rock units that we might find in the field, and made references to the rock units we'd seen on the field activity.

We took about 180 students in 2 consecutive days, with 1/2 the students going each day in 2 different busses, with 3 adults on each bus. One bus started on the MN side, while the other went to WI side first. Then, the two busses switched locations. At the MN visitor center, we had 3 separate groups from Bus A at the Minnesota pothole area. Students rotated between groups every 20 minutes, completing Investigation #1,2, and 3 in about 1 hour. Next, the bus headed to the conglomerate, and finally the Sandstone Bluffs trail, ending with lunch. Bus B started in Wisconsin, with either the pothole trail there, or the visitor center, and then headed to the MN side. The WI side activities could be done with a group of 50, or split into smaller groups as we did in the MN side.

Bathroom facilities were available at either the MN or WI visitor centers and camping areas.

Safety, of course, is an important consideration. Students were briefed on safety guidelines prior to the trip, and signed an agreement to follow them, in addition to parent permission.

Notebook Activities:

Taylors Falls Interstate Park Field Investigation

At Interstate Park, we will be observing three different geologic events in Minnesota's past. Working in teams, we will be making observations and predictions of what happened in the past. At the close of the investigation, we will hypothesize a timeline for the events that occurred.

MINNESOTA SIDE

Site A: The Pothole Area – ignoring the potholes

Activity: Hiking along the pothole trail, but ignoring the potholes for now, we will make observations about the kind of rocks we see here.

What do you notice about the rocks here?

Sketch these rocks in your journal.

What do you think could have created the holes in these rocks?

These holes are called amygdaloids.

How many different lava flows can we find here?

The river turns here. Normally, rivers "like" to flow straight, so what could have caused the turning?

Site B: The Pothole Area – but now looking at the potholes!

What do you notice about the potholes?

What could cause these to form?

Where do you think water has been in the past here?

Site C: The Pothole Area – looking at the river and the bridge

How do you think early settlers used this river?

The name of this town is Taylors Falls. Where are the falls today?

Site D: The Ravine (top of the ravine)

What do you notice about the rock unit in the ravine. What is it made of?

Sketch this rock unit in your journal.

Below this unit, what size are the rocks here (in the ravine bottom)?

Why do you think that is?

Site E: The Sandstone Bluff Trail

Activity: Hiking along the Sandstone Bluff trail, we will make observations about the kind of rocks we see here.

At the base of the trail before going under the road:

What do you notice about the rocks here?

At the top of the bluff:

What do you notice about the rocks here? (Sketch these rocks in your journal.)

What are these rocks made of?

What do you think might have happened here in the past?

What forces cause weathering here?

What could create this valley?

What kind of rocks do you think are on the other side of this valley?

WISCONSIN SIDE

Interpretive Center: List three things you learned in the Ice Age video or saw in the exhibits.

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Horizon Trail: Where did the rocks come from to build the shelter on the trail

Pothole Trail: Compare the width to depth. Measure 5 potholes. Is there a mathematical correlation between width and depth?

Width Depth

Pothole #1:

Pothole #2:

Pothole #3:

Pothole #4:

Pothole #5:

Hypothesis: Why are these potholes smaller than on the Minnesota side?

AFTER THE TRIP:

Activity for Notebook: Draw a cross section of the Taylors Falls area, including basalts, conglomerates, and sandstones. Use your topographic map to help with the elevations.

TIMELINE: See if you can find the right order for these steps in the Geological Timeline for Taylors Falls.

A. A shallow sea begins to surround the basalt bluffs forming islands. Blocks of basalt fall from these bluffs into the sandy ocean seashore, where they are rounded by wave action.

C. The sea continues to grow larger and deeper, eventually covering the basalt islands with hundreds of feet of sand.

E. Glaciers gradually retreat, and the melting forms a very large lake where Lake Superior exists today. The lake gets larger and larger, because it can't empty to the east, where it is blocked by ice

G. The rift stops growing because another continent slams into North America, stopping the plate movement that is creating the rift.

I. Glaciers move through the rift valley, bulldozing away much of the sediments deposited by the shallow seas.

L. Erosion and faulting create high bluffs of basalt.

M. North American continent splits open, forming a rift valley from Canada to Kansas.

N. The rift grows wider as 4 miles of lava erupt in over 10 separate flows.

R. The lake finally overflows its banks, discharging huge amounts of meltwater from glacial Lake Duluth (now Lake Superior), down the present St. Croix River to the Mississippi, eroding the soft sandstones, and forming potholes in the basalt.

S. The glaciers receded and the land uplifts, changing the drainage pattern of Lake Superior.

(Answer Key: It spells MN GLACIER.)

PRE-FIELD ACTIVITY ACTIVITIES:

VISCOUS LIQUIDS

Lab activity to be completed prior to field activity at Taylors Falls:

Viscosity: resistance to flow

Objective: Inquiry activity with viscosity and air bubbles.

Procedure: Students are given 4 clear containers with materials of various viscosities. Suggested would be water, oil, corn syrup, and rubbing alcohol. Students are given the definition of viscosity, and then given the liquids, straws, and antacids (like Alka Seltzer). They determine which liquids are most viscous, and what happens to bubbles blown or created within those liquids.

SANDING ROCKS

Students are given small limestone rocks and varying types of sandpaper. In an outdoor inquiry activity, they sand these rocks to see if they can make them "round". After short bursts of sanding, students estimate how long it would take, with continuous sanding, to create a totally round stone.

8.3.1.1.3 Major geologic events due to plate movement.
8.3.1.2.2. Explain weathering, erosion, and glacial activity in shaping MN landscape.