Chap 10, Sec 3 (From Bedrock to Soil) Objectives: Describe the source of soil. Of what is soil made? What are the layers in the soil profile and what is their function? Describe how various climates affect soil.

Let’s Review More Tech Terms: soil – a loose mixture of geologic (inorganic) and biologic (organic) material that supports the growth of plants. soil horizons – layers of soil that differ in color and texture from the layers above and below. (6 layers: OAEBCR) The amount of sand, silt, and clay, determine a soil’s texture!!!

(Copy the particles & sizes in your IAN from Fig 2 on pg. 289)

Because soils are made from weathered rock fragments, the type of soil that forms depends on the type of rock that weathers. (For example: Granite of Stone Mountain vs. Limestone of Hilton Head Island)! 3) bedrock (R horizon) – the solid layer of rock beneath the soil, that once exposed at the surface, weathers into smaller and smaller particles. (weathered bedrock is the basic material of soil)

Our Angry Earth-worm Brings CO2 to the Roots

4. O horizon – organic, slightly decomposed material from fallen leaves, plants, and animals found in forests. 5. A horizon – topsoil- near surface, and contains the MOST humus of any layer (nutrient rich) 6. E horizon – zone of eluviation and leaching (downward movement of dissolved material)

The example below is of Florida soil leaching – when water dissolves and carries nutrients in the topsoil through the horizons. The example below is of Florida soil

**Soil texture affects the soil’s consistency.** 7. B horizon – subsoil – this horizon collects dissolved substances and nutrients leached from the horizons above – contains little or no humus. 8. C Horizon- weathered parent material – contains only weathered rocks and minerals that come from the bedrock layer beneath. **Soil texture affects the soil’s consistency.** 9. Soil Fertility – the ability of soil to hold and supply nutrients for a plant

Temperate Forest and Grassland Climate Soil Type Characteristics Tropical Rain Forest Nutrient poor Thin topsoil Humid air/warm temps Large amounts of rain Desert Salt creates toxic soil Very little rain Low rate of chemical weathering yields less soil creation Temperate Forest and Grassland Thick fertile soil Frequent changes in temp leading to frost action Receive lots of rain for chemical weathering Arctic Thin and unable to support many plants Limited nutrients Little rain Low soil temps prevent decomposition

Identifying Relationships 1. Which of the following soil properties influences soil moisture? a. soil horizon b. soil fertility c. soil structure d. soil pH 2. Which of the following soil properties influences how nutrients can be dissolved in soil? a. soil texture 3. If a soil sample is 60% sand particles and has 30 million particles of soil, how many of those soil particles are sand? Critical Thinking Identifying Relationships In which type of climate would leaching be more common—tropical rain forest or desert?