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Date:
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Volcano in the lab: Modeling igneous processes in wax and sand
Background:
Scientists know that the outer layer of the earth is made of solid rock. The temperature of the crust
increases with depth, reaching values typically in the range from about 200 °C (392 °F) to 400 °C
(752 °F) at the boundary with the underlying mantle. In fact the temperature increases by as much as
30 °C (about 50 °F) for every kilometer you descend in the upper part of the crust. Based on many
years of investigations, scientists now estimate that the crust of the earth, the solid outer layer, is
about seventy kilometers (forty-four miles) thick at its deepest point. Some parts of the crust, like the
floor of the oceans, may be as little as ten kilometers (six miles) thick. Big pieces of the crust, called
plates, form along cracks or weak spots in the upper mantle. The crust and upper mantle
(lithosphere) comprise the tectonic plates that rest atop the asthenosphere. The huge plates, like
giant rafts, drift on the liquid magma in the mantle.
Beneath the earth’s crust is a layer of rock called the mantle. The earth's mantle is not molten. The
mantle is a solid that moves or deforms under pressure. Most of the mantle, over 99%, remains a
solid, but the high temperature and the push and pull forces cause some of the mantle to melt. This
molten rock is known as magma. Magma rises up towards the earth’s crust. When the pressure within
the magma chamber is greater than the strength of the crust it begins to break through.
Objectives:
 Predict the outcome of heating material layers
 Simulate ways in which both extrusive and intrusive igneous rocks may form
 Observe the sequence of events involved in volcanic activity and explain the outcome
 Describe how the model relates to volcanic activity in the upper mantle - lithosphere
Resource list:
· one 500ml glass beaker
· colored candle wax
· washed sand
· cold water (preferably chilled in a fridge)
· a Bunsen or camping burner, tripod, gauze, heatproof mat, gas supply, matches
· eye protection, or safety screen (when operating the flame or heating the jar)
Prediction: Answer the following question before you begin the lab.
1. Which will melt first – the wax or the sand?
2. What will the heat source under the beaker represent?
Procedure:
1. Place the beaker over your heat source.
2. Heat up the beaker and watch carefully throughout.
3. Remove the heat source once some of the wax has melted (don’t melt the entire layer of wax).
4. Describe in words and with drawings what your volcano looked like after the trial. Use a separate
sheet of paper for your drawings and observations.
5. Label your drawing with the appropriate characteristics and features for igneous intrusions.
Analysis and Conclusions:
1. Explain what the sand and water represented in this activity.
2. Explain what the rising “wax” represents.
3. How do your observations compare with the movement of magma within Earth’s crust?
4. What were you modeling when you heated the base of the beaker?
5. What type of volcanic activity does your model represent?