Magma Motion Lab Report
Name: ________________________________ Partner(s): ________________________
Date: ____________ Period: ______
Middle School Earth Science • Volcanology Lab
Magma Motion: Viscosity & Eruption Dynamics
Investigating how fluid resistance to flow dictates volcanic cone architecture and eruption intensity.
Inquiry Lab
Volcanologist's Field Brief: Viscosity & Magma
Viscosity is a liquid's internal resistance to flow (molecular friction). In nature, magma viscosity depends heavily on its silica content ($SiO_2$) and temperature. Low-silica basaltic magma flows easily (low viscosity) like warm syrup, allowing gases to bubble out gently to build broad shield volcanoes (e.g., Kilauea, Hawaii). High-silica rhyolitic magma is extremely thick and sticky (high viscosity), trapping pressurized gases until they explode violently from steep composite stratovolcanoes (e.g., Mount St. Helens).
Guiding Question & Hypothesis Formulate before testing
Guiding Question: How does fluid viscosity affect down-slope flow velocity and volcano slope structure?
Hypothesis: If a test liquid has a higher viscosity, then its velocity down a 30° inclined track will [ increase / decrease / stay the same ] because
Independent Variable
Type of Liquid
Fluid viscosity / internal resistance
Dependent Variable
Flow Time & Velocity
Seconds over 30 cm distance ($v = d/t$)
Controlled Constants
Ramp Angle & Volume
30° incline, 30 cm track, 5 mL sample
Station Materials
- Incline ramp / cardboard tray
- Wax paper / laminated track
- Metric ruler (30 cm) & tape
- Angle protractor (set to 30°)
- Stopwatch / digital timer
- 5 mL measuring syringe/spoon
- 4 Fluids: Water, Oil, Soap, Syrup
Safety Protocol
Wipe all spills immediately to prevent slip hazards. Never taste lab materials. Dispose of wax paper strips in the designated bin.
Investigation Protocol
- Calibrate Ramp: Prop the incline ramp at an angle of exactly 30° using textbooks and your protractor. Affix a clean wax paper track.
- Mark Boundaries: Use a permanent marker to draw a START LINE 5 cm from the top and a FINISH LINE exactly 30 cm down the slope.
- Load Sample: Measure precisely 5 mL of Liquid 1 into your dropper or measuring syringe. Hold the nozzle directly over the start line.
- Release & Time: Dispense the liquid and simultaneously start the timer. Stop timing the instant the leading edge of the liquid touches the finish line.
- Replicate & Repeat: Record the elapsed time to the nearest 0.1 second. Complete 3 trials for each liquid, calculating the average time and speed.
Unit 4: Earth Surface Processes & Volcanology Page 1 of 3 • Investigation Design
Part 2: Quantitative Collection & Visualization
Lava Flow Velocity Data & Graphing Studio
Track Distance ($d$): 30.0 cm
Ramp Incline Angle: 30°
Table 1: Flow Duration & Speed Calculations Formula: $\text{Flow Velocity } (v) = \frac{\text{Distance }(30\text{ cm})}{\text{Mean Time }(s)}$
| Test Liquid (Fluid Model) |
Predicted Viscosity |
Trial 1 ($s$) |
Trial 2 ($s$) |
Trial 3 ($s$) |
Mean Time ($\bar{t}$) |
Velocity ($cm/s$) |
| 1. Water Basaltic / Runny model |
Low |
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| 2. Vegetable Oil Moderate flow model |
Medium-Low |
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| 3. Liquid Dish Soap Andesitic intermediate |
Medium-High |
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| 4. Corn Syrup / Molasses Rhyolitic / Sticky model |
High |
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| 5. ____________________ (Optional / Inquiry Fluid) |
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Graph Title: Fluid Flow Velocity vs. Liquid Type (Viscosity Model)
T: Title A: Axes I: Interval L: Labels S: Scale
Flow Velocity (cm / s)
___ ___ ___ ___ ___ ___ ___ ___ ___ ___ 0
Water
Veg. Oil
Dish Soap
Corn Syrup
Liquid 5
Independent Variable: Tested Fluids (Low Viscosity $\longrightarrow$ High Viscosity)
Graph Type: Bar Graph or Scatter Plot
Plot each liquid's average flow velocity ($cm/s$). Use a colored pencil to construct vertical bars or plot data coordinates clearly.
Key / Qualitative Observations:
Note any sheet-spreading, droplet bead formation, or track friction observed during descent.
Unit 4: Earth Surface Processes & Volcanology Page 2 of 3 • Data Collection & Graphing
Part 3: Scientific Reasoning & Volcanic Application
Analysis & Volcanology Synthesis
Evidence-Based Argumentation
1. Data Trend & Flow Rate: Based on your completed graph, rank your four tested liquids from lowest to highest velocity. What mathematical relationship exists between liquid viscosity and the time required to travel 30 cm?
2. Particle-Level Mechanics: How did the internal resistance (friction between molecules) of the corn syrup compare to that of water? Explain why gravitational pull alone could not accelerate the syrup down the ramp at the same speed as water.
Connecting Lab Models to Real Volcanic Landforms
Shield Volcano (e.g., Mauna Loa) Basaltic Lava
Characteristics: Low silica ($<50\%$), high temperature ($1200^\circ\text{C}$), very low viscosity. Lava travels dozens of miles before solidifying, creating gentle, broad slopes and effusive fountains.
Composite / Stratovolcano (e.g., Mt. St. Helens) Rhyolitic / Andesitic
Characteristics: High silica ($>65\%$), lower temperature ($800^\circ\text{C}$), extremely high viscosity. Sticky magma blocks vents and traps pressurized $H_2O$ and $CO_2$ gases, causing cataclysmic explosive eruptions.
3. Hazard Evaluation: Which tested liquid served as the best model for basaltic lava, and which modeled rhyolitic magma? Why do high-viscosity volcanoes pose a catastrophic explosive hazard to human cities compared to low-viscosity shield volcanoes?
Final Scientific Conclusion (CER Framework) Synthesize your experimental findings
CLAIM: Directly answer: How does magma viscosity govern volcanic cone slope and eruption style?
EVIDENCE: Cite specific quantitative data (mean times or flow velocities) comparing at least two test fluids:
REASONING: Connect your data to silica chemistry, resistance to flow, and gas entrapment in magma chambers:
Unit 4: Earth Surface Processes & Volcanology Page 3 of 3 • Scientific Synthesis & CER
