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Soil Analysis Comparison Dashboard

Run the Soil Analysis Dashboard Fullscreen

About This MicroSim

Soil is one of the most useful kinds of trace evidence because it is different almost everywhere. The dirt on a suspect's boots carries a fingerprint of where they have been — its color, the mix of gravel, sand, silt and clay, its acidity, and the layers it forms when spun in a density column.

This dashboard puts a questioned soil sample (from a suspect's boots) next to three reference samples from known locations and lets you compare all four criteria at once. You decide which reference best matches the questioned soil, and the Match Score button checks your reasoning with a number.

How to Use It

  1. The dashboard has four panels, one per comparison criterion:
    • Soil Color (Munsell): standardized color chips and their notation.
    • Particle Size (%): a stacked bar of gravel / sand / silt / clay.
    • pH (0–14): each sample's acidity marked on an acid-to-base scale.
    • Density-Gradient Bands: the layered pattern the soil forms in a column.
  2. Each panel shows the same four samples as columns: Questioned (orange) and References A, B, C.
  3. Click any reference column (A, B, or C) to select it. It is highlighted across every panel for a side-by-side comparison with the questioned sample.
  4. In the gradient-tube panel, the selected reference's bands are outlined green where they line up with a questioned band and red where they do not.
  5. Press Match Score to compute a weighted similarity (color, pH, particle size, and band match) as a percentage.
  6. Press New Case to load a different questioned sample and reference set.
  7. Hover over any panel for a note on why that criterion matters in court.

What You Can Learn

  • Compare two soil samples across four independent properties instead of just one.
  • See why a single matching property is weak evidence but agreement across all four is strong.
  • Read real numbers — pH and particle-size percentages — rather than eyeballing.
  • Understand how a density-gradient column separates soil into mineral bands and why matching bands are so discriminating.

You can embed this MicroSim on your own web page with this iframe:

<iframe src="https://dmccreary.github.io/forensic-science/sims/soil-analysis-dashboard/main.html"
        width="100%" height="602" scrolling="no"></iframe>

Lesson Plan

Audience: High-school forensic science (grades 9–12) Time: 10–15 minutes Bloom level: Analyze (L4) — compare.

Worked example. In the default case, click Reference A and press Match Score — it scores low, with a high pH, a sandy particle mix, and mostly red (non-aligning) gradient bands. Now click Reference C and score it again: the color, pH, particle ratios, and bands all agree, and the score is high. Reference C is the soil's true collection location.

Guided questions:

  • Which reference matches the questioned sample on color but not on pH? What does that tell you about relying on color alone?
  • Look only at the particle-size panel. Which reference has the most similar gravel/sand/silt/clay mix to the questioned sample?
  • In the gradient-tube panel, which reference has the most green (matching) bands? Why are aligned bands such strong evidence?
  • Rank References A, B, and C from best match to worst, then check your ranking with the Match Score. Did any criterion mislead you on its own?

Extension. Press New Case and work through it without looking at the Match Score first. Write down which reference you think matches and your reasoning across all four criteria, then reveal the score to check yourself.

References

Specification

This MicroSim was generated from a specification in Chapter 5: Glass, Soil, and Physical Trace Evidence.

Design note: the samples, colors, and band patterns are illustrative teaching data, not measurements from a real case. Real soil comparison uses many more properties (mineralogy, pollen, microfossils, organic content) and is reported by a qualified examiner rather than a single percentage.