Investigating sedimentary rock deposition and weathering in Mawikwe Bay Sea Caves

Students will recognize that the sea caves were formed from the deposition of sandstone rock by rivers. Students will identify layers of rock that are more or less resistant to weathering. Students will identify wave action as the main cause of weathering, with ice, plants, and animals contributing to weathering.

This specific activity must be done in the winter after safe ice conditions on Lake Superior have been confirmed. A half day, at minimum, should be committed to the field investigation. Students should be able to identify and explain the three main types of rocks and the rock cycle, and they will be familiar with local geology. This could be used as a culminating activity near the end of the study of the rock cycle, deposition, or weathering. Students should already be comfortable with inquiry activities, in which they are guided to observe, ask questions, investigate answers, and share results.

The Mawikwe Bay Sea Caves are found along the southern shoreline of Lake Superior in northern Wisconsin, east of Cornucopia, and west of Bayfield. The caves are accessible only by water in the non-ice seasons, and by ice during the winter. The caves are made of sandstone that was deposited by braided rivers which have then been highly weathered by Lake Superior wave action.

Activity Description:
Students will hike along the frozen shoreline of Lake Superior to investigate the Mawike Bay Sea Caves, part of the Apostle Islands National Lakeshore in northern Wisconsin.
A. Students will be allowed some time to explore the sea caves prior to beginning the activities.
B. Students should sketch a section of the cliffs, specifically indicating boundaries between layers and areas of greater or less resistance to weathering.
C.Students will work in small groups to complete an inquiry investigation, based on the "Teachers 12-Step Program for Inquiry-based Field Investigations."

1. Working in small groups, make observations
2. Record observations
3. Large group discussion and questions
4. Teacher-guided question formation
5. Students select a question
6. Students design a study
7. Collect data
8. Modify procedures
9. Analyze results
10. Share data
11.Generate hypotheses
12. Present results

Presentation of results can be made informally at the field site, and then posters created and presented more formally in the classroom.

During the question selection step, the teacher should guide some groups to follow individual layers of sandstone along the cliff face. Also, some groups should be encouraged to investigate the various weathering rates of different layers of sandstone.

1.Lake Superior ice conditions along the sea caves can be obtained by contacting the Apostle Islands National Lakeshore Visitor Center. Buses can park at the end of Myers Beach road, where by hiking down to the water and eastward, students and staff will reach the sea caves. Depending on snow conditions, snow shoes or skis may be used to aid transportation to the caves.
A backpack containing measuring equipment should be brought to the site.

Students will be assessed on their participation, notes and sketches during the field investigation. They will also complete a write up of their results when they return to the classroom.

Minnesota Academic Standards:
8.III.A.2 weathering and sediment deposition
8.III.A.3 rock cycle
8.III.A.5 constructive and destructive processes

Wisconsin Model Academic Standards:
C.8.7 explain conclusions
E.8.3 forces changing earth
E.8.5 geological history