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2.5: Activity 4- Rocks to Parent Material

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    Development of rocks into parent material that becomes soil

    As mentioned above, inorganic parent materials are typically derived from a variety of geological species. These parent materials are typically identified by their mode of transportation (i.e. colluvium transported by gravity, or loess transported by wind), however, it is important to recognize how specific rock types physically weather in order to be able to identify parent materials properly in the field.

    Observe the trays of parent materials and soil for the granite and sandstone rocks on display. The first tray contains the fresh rocks before being weathered, the second tray contains the parent material of the soil formed from this rock, and the third tray contains the soil formed from the parent material derived from this rock type.

    1) List the main minerals in each type of rock.



    2) What main physical changes (particle size and color) have occurred in the stages from rock to weathered rock to soil?

    3) Which fraction—rock, weathered rock, or soil (circle one)—is most susceptible to further physical and chemical weathering? Why?

    4) You will drop some hydrochloric acid (HCl) (a few drops) on each fraction (rock, weathered rock, and soil). Indicate which materials fizz by filling in the table below with a “Y” for yes and an “N” for no.

    Rock Type Rock (R)

    Weathered rock parent material (Cr)


    5) What is the reason (which reaction is responsible) for the fizzing?

    REMINDERS/Assignments for next week’s lab:

    a) Study for pre-lab Quiz on material from Lab #3: Soil Taxonomy.

    b) Complete pre-class activity: classified location exercise (Lab 3) c) Next week we will prep bulk density samples for an upcoming lab on Soil Physical Properties.

    c) Next week we will prep bulk density samples for an upcoming lab on Soil Physical Properties.

    This page titled 2.5: Activity 4- Rocks to Parent Material is shared under a CC BY 4.0 license and was authored, remixed, and/or curated by Anna R. Schwyter & Karen L. Vaughan (UW Open Education Resources (OER)) via source content that was edited to the style and standards of the LibreTexts platform; a detailed edit history is available upon request.