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The Unknown Soils Lab
Stereoscopic Examination Gross Observation Water Sorted Observations Lab Introduction: In this lab your team will investigate 3 samples of soil. Your team's goal is to identify which layers, or horizons, each type of soil comes from. Your partners and you will collect data microscopically, by gross observation and by soil sorting. Once your team has collected the required data, you will analyze the data and tell which layer each sample comes from, while giving good reasons to support your conclusion.
Please review the information below before you begin the lab.
Soil forms by the processes of physical, biological and chemical weathering.
Most soil is a mixture of three basic components, weathered rock, or sand, mineral fragments, and clay. Soil has three other key components. organic matter (recycled plants, fungi, animals etc.), water and air.
Soil formation &endash; Let's pretend the ground is just bare rock and see what happens over time.
C Horizon: Bedrock breaks down due to physical weathering by water and wind. Water freezes and thaws in rock cracks, breaking the rocks. Also, the wind sand-blasts the rock, further breaking down the rock. Rocks also break down from chemical weathering. For example, acid breaks down rocks chemically. So slowly, but surely, the C Horizon forms from the bedrock.
B horizon: As plants begin to grow on the weathered rock of the C horizon weathering continues. Biological weathering from plant roots kicks in to break the rock down more. Eventually a new layer of soil forms on top, the B horizon.
O and A horizons: These top two layers build up and form together. The O, or organic layer, forms from fallen leaves, sticks, and decaying animals. The O horizon is also called the litter layer in forests. As matter in the O horizon decays and accumulates over many years, the decomposed matter and nutrients mix with the soil below.
This mixture forms a rich layer of soil called the topsoil or A horizon. The A layer, also called humus, is extremely biologically active. As long as there is no disturbance occurs, (volcanoes, earthquakes etc.) the plants, worms, insects, fungi, and bacteria living in both top layers decay to add more organic matter. This adds to the topsoil. (In the Midwest some topsoil layers are over 6 foot thick!) Over the years, rains slowly wash nutrients into the B Horizon, enriching this layer.
Unknown Soils Laboratory Conclusion Format: please follow the format
Conclusion for Sample__A… B… or C____
a. Initial Prediction. (format = Sample A is from the ___ layer because __ give at least one scientific observation to support the prediction.)b. Final Conclusion: Sample ____ is from the _____ layer.
c. Key Supporting information. Here's how I came to this conclusion……
Minimum of 4 key facts required. At LEAST One fact must be Quantitative!
Tell how using at least:
1. One + key observation from Data Table One - Soil Observations
2. One + key observation from the Water Sorted Observations
3. One + key observation from the Stereo Micro Figure.
d. Closing statement &endash;
Repeat this format for all three Samples. (30 pt each!)
Hidden EC Questions (5pt each, 20 pt total)
1. Describe two ways that humans can help build soil.
2. Explain two reasons why we don't see a huge amount of leaves and dead animals building up in the soil over time. (What happens to most of this material?)
3. Be specific - tell one new thing you learned from this lab.
4. What was your favorite part of this lab?
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