Investigating Lava Flows and Their Imapct on Shoreline Features

Margie Menzies, Harbor City International School, Duluth, Minnesota, participant in TIMES XII.
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Summary

In this field geology activity, students will explore basaltic lava flows along the shoreline of Lake Superior, and begin to gain an understanding of the geologic story of Minnesota's North Shore. They will make observations about features seen in the flows and determine where they are likely to occur in a lava flow by making a drawing of a lava flow from top to bottom including the features they discovered in the field. They will correlate the features they observe with the shape of the shoreline looking for the geologic story of this beach.

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Learning Goals

Learning goals:
This activity is designed for students to
-Make observations about characteristics of lava flows in the field
-Sketch different types of features observed and make a prediction as to why they formed and then represent them in a drawing from top to bottom of a lava flow
-Connect the lava flow features with the topography of the area and analyze their relationship to each other and gain an understanding of why our area looks the way it does.

Key Concepts:

1. Different features in a flow correlate to the position within the flow where they occur.
2. Understanding the occurrence and types of lava flows is key to understanding the existing topography of the North Shore of Lake Superior.
3.Volcanic lava flow and the Rift flow that occurred on Minnesota's North shore differ in some ways and are similar in others.

Vocabulary:
-Mafic
-Columnar Jointing
-Amygdules
-Pahoehoe
-Vesicles

Context for Use

Context for Use:
This activity is designed for a fall earth science class focusing on geology for 9-12 students in a public charter school. Class sizes are generally 18-20 students and are structured in two and a half hour block segments that meets once a week. It is intended as an introduction to volcanic flow characteristics through observations and sketches made in the field. It is designed to fit within the regular class period early in the fall, and students will likely have had only one or two classes prior to the field trip. Therefore there will not have had much instruction time prior to the investigation on specifics of mafic and felsic rocks and their corresponding lava flow types and students will largely be dependent on any prior knowledge they bring to the class. The main idea is working with students to develop regular and effective use of a course journal and making thorough observations and sketches in the field. The general concepts of making and recording observations and later tying that to specific types of geologic formations should be effective in a wide variety of settings, though some adaptation is necessary for those with class periods shorter than the alloted two and a half hours.

Description and Teaching Materials

Activity Description:
Location: Stretch of public beach just north of Kitchi Gammi Park on Scenic Highway 61, accessible from roadside pull-off picnic area/rest stop.

Materials:
-Journals
-Writing materials including colored pencils
-Digital cameras (optional) for additional documentation
-Hand lenses
-Optional additional materials for more extensive investigation such as measuring tools

Prior to trip: Students will have met only a couple of times. We will have done some basic observation and sketching activities indoors using the Earth Science Pic of the Day website (http://epod.usra.edu/archive.php3) Students will begin the process of making observations to attempt to tell the story of a landscape geologically. We will also have done an activity with "geology event blocks" which have a series of 12-14 things that have been done to the block and students must identify and determine the order of the sequence of events. We may have spent some time on the Lakewalk area in Duluth identifying rocks and exploring geologic features. Students will have been paired with a partner to work with the week before the trip, and cautioned about being prepared for the weather and wearing appropriate shoes and clothing. Students will have been informed about the purpose of the trip and their journaling skills warmed up in the classroom prior to the trip. Arrangements will have been made for transportation ahead of time, and the weather on the day of the trip needs to be dry and Lake Superior waves fairly calm. An alternative date will be arranged in advance as well.

Field Trip day:
1. Students will arrive prepared with materials and appropriate clothing for field investigation.
2. Bus will be loaded and transport to location will take approximately 20 minutes.
3. At field trip site, students will be lead to beach access as a group. Once we have arrived at the beach, student teams will be assigned a specific section of beach to explore in depth and told that they are working in a lava flow area. Sample areas will be fairly small, no larger than about 5 feet by 5 feet. At their assigned section students will be assigned to make detailed observations of their small section and make a detailed sketch in their field notebook of notable features, characteristics, rock color and texture, etc. They will also be asked to make some guesses about how significant features formed. This will be allotted about 20 minutes of time.
4. After doing their observations students will assemble again as a large group and be asked to summarize for the group about the features they observed and their guesses as to how they formed and point out where they were exploring.
5. After the group discussion, students will be given time to explore other groups areas, with the challenge to figure out how you can tell the top from the bottom of a lava flow and make a drawing to include all of the features they have seen and where they think they fit in a flow from top to bottom, and cautioned that they have not yet seen all of the features of the lava flow and told that there are more between their location and the parking area. Students will be given a map of the shoreline and told to explore the area between the exploration area and the rest stop noting features on their maps trying to determine how many layers of flow there are in the area, and to look for any correlation there might be between the lava flows and the shape of the shoreline. They will be given about an hour for this exploration and instructions on where to stop on the beach, and should arrive with a drawing of a lava flows features top to bottom as well as notes on their map of the shore line tying in where they saw the features and how they might be connected to the shoreline shape.
6. At the meeting location group we will spend about 10-15 minutes debriefing in the field and correlating their results roughly with the intent to spend more time back in the classroom the next time we are scheduled to meet. Diagrams and maps will be collected.
7. At the next class meeting, students will be given back their drawings and maps and given a drawing of typical lava flow features. They will be asked to compare and see how what they observed correlates to the drawing. Were there features represented in the drawing that we did not see at the beach, did they add others that were not on the drawing? Should there be more features on the drawing? Was this beach a good representation of a lava flow? Why or why not? What questions do they still have? Is there other information that they think they need to complete the geologic story of this beach area? Did this activity help them understand the geologic features of our area better? Did it leave them with things that they can watch for in the field in the future? How might a volcanic flow look different from the rift flow of this area? Lakewood Base Map (Acrobat (PDF) 6.2MB Aug22 08)

Teaching Notes and Tips

Teaching Notes and Tips
In this field exploration, safety is a primary concern. A field first aid kit will be carried on this and all field activities. Students will be given expectations about where they can explore and cautions about walking on Lake Superior shoreline such as watching for wet slippery rock, and that weathered rock doesn't always provide as firm a foundation as it may appear at a glance. They will be cautioned to stay with their group and to work together.

Time management will be critical and this will need to be explained to students in advance so they understand clearly what the expected outcomes are for the field activity. This is a new activity for me and one I will no doubt find has things I haven't thought of yet and will want to revise later.

This activity and some of the content is new material for my Earth Science I class. In the past, I had not used this beach or even known about the features available for students to see so close to home. Volcanoes and the mid-continental rift in this area have been small pieces of what I have discussed with students. We have primarily relied on prepared material that looks at different types of volcanic flow, but no exploration of features of flow or what to look for locally. I'm excited to add this component to my curriculum and know from past experience that students respond to observations in the field much readily than classroom discussions. Understanding your own backyard is a way of adding authenticity to curriculum, and helping to determine why it matters.

Assessment

Assessment
Assessment tools that will be used in this activity include the following:
Use of journal in the field for taking recording observations and noting questions. As well as active demonstration of activity participation.
Field drawing of layers of a lava flow.
Map of shoreline with flows and features mapped.
Question on Earth Science I final regarding their observations and conclusions.

Standards

Standards Match
9-12 IIIA.6- students will describe the rock cycle and compare and contrast the processes responsible for the formation of igneous, sedimentary and metamorphic rocks.

References and Resources