Lesson Plan

Fire and Ice

Grade Level:: Middle School: Sixth Grade through Eighth Grade
Subject:: Science
Lesson Duration:: 90 Minutes
Common Core Standards:: 6-8.RST.3, 6-8.RST.7, 6-8.RST.8, 6-8.RST.9
State Standards:: Washington State Science Standard EALR 4 Earth and Space Science - Grades 6-8 Cycles in Earth Systems
Thinking Skills:: Understanding: Understand the main idea of material heard, viewed, or read. Interpret or summarize the ideas in own words. Applying: Apply an abstract idea in a concrete situation to solve a problem or relate it to a prior experience. Analyzing: Break down a concept or idea into parts and show the relationships among the parts. Creating: Bring together parts (elements, compounds) of knowledge to form a whole and build relationships for NEW situations.

Objective

Students use ice cream glaciers and hot wax lava flows to simulate the interactions of glaciers and lava flows. By the end of the lesson, students will be able to answer the question:

How do a volcano and its glaciers work together, specifically at Mount Rainier?

Background

Glaciers and Mount Rainier co-exist as a dynamic system

Mount Rainier distinguishes itself among other Cascade volcanoes because of its widespread high-altitude slopes and extensive snow and ice cover. About 88 square kilometers (34 square miles) of snow and ice cover the mountain at summer’s end. Glaciers have covered Mount Rainier over much of the volcano’s 500,000-year lifespan, creating a dynamic system. The volcano provides high-elevation slopes that are conducive to glacier formation and glacial erosion. Volcanic eruptions can melt snow and ice, even while glaciers influence the movement of lava flows. A general list of mechanisms of influence between glaciers and volcanoes is shown in the sidebar. This information is depicted in graphics “Glaciers on Mount Rainier,” “Columbia Crest Summit,” and “Glacier-Volcano Interactions.”

Ice-age glaciers envelop Mount Rainier

To understand the extent to which hot volcanic rocks have interacted with surrounding glaciers, we need to put on our "glacier glasses" and envision landscapes largely buried by ice. During ice ages that occurred repeatedly between approximately 1.8 million and 11,000 years ago, large ice sheets covered northern Europe and much of Canada and the northern United States, including the Puget Sound area. Mountain ranges in the western United States, including the Cascades were mantled by extensive glaciers. Some of the glaciers on Mount Rainier were hundreds of meters (1,000 feet or more) thick on the flanks of the volcano and almost 1,000 meters (3,000 feet) thick in valleys at the base of the cone. Mountain glaciers coalesced and flowed for one hundred kilometers (sixty miles). Glacier ice covered the locations of the present day communities of Ashford, Alder, Green water, and Carbonado. Around 15,000 years ago, these enormous glaciers began to thin and recede into existing valleys. Their descendants cover much of Mount Rainier today. View the extents of glaciers then and now in the graphic "Maximum Extent of Glaciers on Mount Rainier During the Ice Ages."

Mount Rainier erupted repeatedly while buried by ice-age glaciers
Mount Rainier erupted repeatedly during past ice ages. The co-existence of volcanic and glacial processes led to a variety of interactions that shaped the mountain in a unique way. The origins of these features can be understood only when the interactions of the glaciers and volcanic forces are recognized.

When lava meets ice

During times of extensive glaciation, lava poured repeatedly from the summit vent of Mount Rainier and encountered glaciers. In the contest between lava flows, rock, and ice, glaciers at first appear to be less durable. In theory, a lava flow can melt about ten times its volume of ice, though it rarely does so. We commonly think of lava flows as bullish, relentless, and unstoppable. However, observations at ice-clad volcanoes around the world prove that glaciers can survive the onslaught of heat from lava flows. In some situations, glaciers can exert some control over the movement of lava flows, and as such are the architects of Mount Rainier. Consider these mechanisms.

Lava flows tumble and disintegrate on steep slopes – Lava that flows over steep slopes often breaks apart and plunges onto the glacier, where it cools as rock debris. Sometimes the fragmenting lava flow forms a turbulent avalanche of scorching hot rock and gas called a pyroclastic flow, which can sweep across the snow and ice. Incorporation of snow and ice into the pyroclastic flow can cause the flow to transform into a volcanic mudflow (lahar). Lahar layers are found in river valleys that extend from Mount Rainier.
Ice-age glaciers act as physical and thermal barriers to lava flows – An advancing lava flow melts downward through thick ice until it contacts bedrock, where it chills and hardens, confined within the glacier. After the eruption, glacier ice often flows across the hardened lava flow. By this mechanism, Mount Rainier gains volume, and retains its glacier cover. Some of these lava flows, now partially eroded, are visible as ledges on the flanks of Mount Rainier.
Thin ice and ice-free regions allow lava flows to travel far – Lava encounters less resistance in the thin ice and ice-free ridges between thick valley glaciers. The lava flow's outer skin cools and hardens, while the interior of the flow remains fluid and travels many kilometers (miles) from the base of the volcano. Over time, successive stacks of elongated lava flows have built ridges—from the bottom up—in a pattern that radiates from the cone of Mount Rainier. Paradise Ridge, Mazama Ridge, Rampart Ridge, and Emerald Ridge are some examples of this phenomenon. This interaction is depicted in the graphic "How Lava Ridges are Made." The phenomenon can happen only when glaciers envelop Mount Rainier, such as during an ice age.

More about glaciers

A glacier is a large mass of flowing ice formed by the compaction and recrystallization of snow that has accumulated over a period of years. When snow crystals land atop one another their fragile edges snap and break. Pressure from overlying snowpack settles the crystals, squeezes out adjacent air pockets, forces them to liquefy and then recrystallize as ice. By these processes, delicate snow crystals transform into a strong lattice of ice crystals that has sufficient strength to transform the landscape.

Glaciers as sculptors

Glaciers are well known as sculptors of the landscape, but the true artist is rock debris encased within the ice. Landslides and rock fall produce rock debris that drops onto the glacier surface. Winter snow falls bury the rock debris. Snow surrounding this rock debris transforms to ice. Eventually some of the entrapped rocks touch the valley floor and walls where they scrape and polish, as with grit in a gem polishing machine. Millennia of erosion by glaciers are responsible in part for the characteristic U-shaped valleys. See glacial scratches (striations) depicted in the graphic "Glacial Scratches (Striations) on Lava Rock at Mount Rainier."

Present-day glaciers at Mount Rainier

While Ice-Age glaciers have thinned and receded dramatically over the last 15, 000 years, Mount Rainier still hosts one of North America's largest single peak glacier systems. The present glaciers consist of approximately 4.4 cubic kilometers (one cubic mile). For scale, imagine an ice cream scoop the size of Seattle's Safeco Field sports stadium. Removing all the perennial (long-lasting) snow and glacier ice from Mount Rainier would require 2,600 stadium-sized scoops! Envision this also as an ice cube one mile on a side. The volume of perennial snow and glacier ice on Mount Rainier is equivalent to the amount of ice on all the other Cascade volcanoes combined.

Preparation

*Decide to project images or make copies for students of the following:

Graphic “Glacier Scratches (Striations) on Lava Rock at Mount Rainier”
Graphic “Volcanic Rocks of Modern Mount Rainier”
Graphic “Lava flows-Experimental and Real World Comparisons”
Graphic “Glaciers on Mount Rainier”
Graphic “Columbia Crest Summit”
Graphic “Glacier-Volcano Interactions”
Graphic “Maximum Extent of Glaciers on Mt Rainier During Ice Ages”
Graphic “How Lava Ridges are Made”

*Decide whether you will conduct this activity as a demonstration or with student groups. Student groups will require multiple amounts of items listed in “Materials,” and additional time for setup. Students build their model, and then make repeated trips to the source of the molten wax on a stove top or hot plate. Note: A demonstration can be accomplished in less time, but will require you to assemble the wax papered tray and volcano model, and to break crayons and melt the wax prior to the beginning of class. If conducting the demonstration with several classes, consider constructing ice age glaciers with the first class and adding one or more layers of wax “lava” with each successive class, followed by examination of the model the next day.

*Put together the ingredients required for each model:

Metal cookie tray with sides (1/2 inch high minimum)
Cereal bowl
Wax paper
Masking tape
Modeling clay (8 oz per model group; black illustrates solidified lava well)
Ice cream (one quart; vanilla illustrates glacier ice well)
Ice cream scoop
Household wax (one pound; used for canning, candle making; also called “Home Canning Wax,” or “Paraffin”)
Crayons (four different colors - quality crayons work best; do not use water soluble crayons)
Scissors to cut clay strips-for use with soft clay only (optional)
Camera (optional)

*Decide whether to assign students with homework that investigates glaciers, ice ages, and glacier-ice interactions ( Procedure Part I Number 2) prior to performing the activity.

*As you prepare for post-activity discussion, keep in mind that no two completed volcanoes models will be alike. On these models, both ice cream glaciers and the older clay lava flows can influence the route of young wax lava flows. Students might observe that successive pourings of wax cause “stacking” of lava flows, as produced at Mount Rainier during the ice ages. Remind students that they should make general observations about melting of ice cream glaciers, the size, shape and overlapping nature of lava flow layers, and any interactions of wax lava flows with the tray rim. Be prepared for a variety of results.