Soils Exam 1 Past Exam Questions

define the term soil structure

aggregation of primarily (1°) soil particles into secondary (2°) structure

Identify and briefly tell me about the 3 components used to describe soil structure

To identify soil structure you base it off the percentage and type of the primary particles. Sand is 0.05mm-2mm, silt is 0.002mm-0.05mm, and clay is <0.002mm. These particles forms peds that are defined by their shape. Then described based on the quality of the ped formations. Classifying them as poor, medium, or well formed. 

Describe Jenny’s state model of soil formation. Identify and briefly describe each component.

Jenny’s state model of soil formation includes 5 factors. Time, climate, topography, biota and parent material. topography effects the drainage class based off the slope. Parent material is dependent on the method of deposition, wind watr or glaciers. Climate is effected by temperature and precipitation. Biota, like decomposers and plant root structure. And lastly time, which is changed based off geological scale.

Considering soil at the local scale, illustrate the 4 components and their relative percentages. Describe each of the 4 components with a single sentence. 

The mineral in the soil is the abiotic soil solids. The organic material is residual from organisms in the process of decomposition. The air and water make up the spare space. If that space is filled with water the soil will be anaerobic, if all by air it will be dry. 

Chart: 20-30% air

20-30% water

45% mineral

5% organic matter

Summarize the main point of the tragedy of the commons.

In the article The Tragedy of the Commons by Garret Hardin, It is discussed the idea of shared resources. It is explained that the resources are being exploited past levels of sustainability. Specifically due to individuals’ greed and overpopulation. The solution proposed was to regulate the resources to prevent overuse. it is also discussed to find creative solutions to relieve these resources.

Q1: The munsell system, used widely to objectively convey soil color. What are the 3 variables. 

Q2: How is the notion describing each ccolor written? 

A1: Hue: The wavelength of the observed color

Value: The relative lightness or darkness within the wavelength

Chroma: The brightness or dullness within that value

A2: The hue is denoted with a large letter, the value is a numeric subscript and the chroma is denoted by a letter. 

Define the term catena and give an example of a catena examined in lab.

A catena i a group of soils that all share the same parent material but have different topography that leads to a different drainage class. a catena studied in lab was at Heiberg forest. the presence of a fragipan and topography led to the soil across the catena to have a different drainage class. 

Rank the following minerals by INCREASING resistance to weathering. Calcite, feldspar, olivine, Fe oxide clays, muscovite.

(Least)calcite→olivine→muscovite→feldspar→Fe oxide clays(Most)

Soil series is the finest level of classification for soils. What are the key variables used to separate/differentiate soil series?

Soil series can be differentiated by solum depth, parent material, coarse fragment percentage and drainage class. Solum depth can be determined visually by seeing where the A horizon begins and where the B horizon ends. The parent material is most similar to the regolith layer. The coarse fragment percentage is the percentage of rocks present within the soil. The drainage class can be determined by visually looking at mottling levels. Using colors can also be helpful by following the munsell system of hue value and color.

What is a drumlin and how is it formed? 

A drumlin is a cigar-shaped topographical feature. It is formed when glaciers move down creating mounds by moving sediments. 

Describe the process model of formation?

Addition: New materials are being added from new organic debree or from soil created through weathering.

Loess: Soil that is lost through leaching and erosion

Transformation: mineral weathering and OM breakdown

translocation: Organic and inorganic material, laterally and vertically.

rank the following mineral by increasing resistence to weathering. Biotite, quartz, hornblende, silicate clays, gypsum.

(Least), gypsum→biotite→Hornblende→silicate clays→Quartz(most)

Considering soil as a system at the global scale, use a diagram to illustrate where soil fits within the global system components> Briefly describe the global system components.

In between the atmosphere, lithosphere, and hydrosphere