Soil Science Overview

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Questions and Answers

Why is soil considered an interface in the Earth system?

It's a common boundary where different parts of a system interact. Soil forms where the solid earth, atmosphere, hydrosphere, and biosphere meet.

What are the four components of soil?

45% mineral matter; 25% air; 25% water; 5% organic matter.

How is regolith different from soil?

Regolith is the layer of rock and mineral fragments produced by weathering, while soil is part of the regolith that supports plant growth.

What's the difference between sand and clay with regard to texture/grain size?

Sand is large-sized grain and more coarse; clay is smaller in size and more fine. Signup and view all the answers

Why is texture an important soil property?

It strongly influences the soil's ability to retain and transmit water and air, both of which are essential to plant growth. Signup and view all the answers

What is loam?

An even mixture of all three sizes (sand, silt, and clay); neither of the sizes is more than the other; loam soils are best suited for plant life. Signup and view all the answers

What is 'soil structure'?

Soil structure refers to the arrangement of soil particles and the pores between them. Signup and view all the answers

List the four soil structures and the infiltration of each.

Platy & spheroidal - slower movement of nutrients to plant roots; prismatic & blocky - moderate water infiltration. Signup and view all the answers

The five basic controls of soil formation are: __________.

parent material, climate, topography, organisms, and time. Signup and view all the answers

How do soil-forming processes operate?

From the surface downward. Signup and view all the answers

Describe the horizons (zones or layers of soil) in temperate regions.

There are 5 horizons in temperate regions from top surface to bottom: O, A, E, B, and C. At the bottom is unweathered parent material. Signup and view all the answers

What horizons does the topsoil consist of?

O and A. Signup and view all the answers

What horizons does the solum layer consist of?

O, A, E, & B. Signup and view all the answers

What is another name for the solum layer?

True soil. Signup and view all the answers

What horizon does the subsoil consist of?

B. Signup and view all the answers

Name and define 4 features or processes of soil formation.

Eluviation, leaching, zone of accumulation, and hardpan. Signup and view all the answers

Why are soils classified?

To emphasize chemical and physical properties of the soil profile based on observable soil characteristics. Signup and view all the answers

How many soils are named in the Soil Taxonomy system?

12 soils. Signup and view all the answers

How many hierarchical categories are there in the Soil Taxonomy system?

6 hierarchical categories. Signup and view all the answers

What language origin are the names in the Soil Taxonomy system derived from?

Latin and Greek. Signup and view all the answers

What is the Soil Taxonomy system useful for?

Useful for agricultural and related land-use purposes. Signup and view all the answers

What is soil erosion?

A natural process in which erosional forces, especially water and wind, move soil components from one place to another. Signup and view all the answers

What are the 4 factors affecting the natural rate of soil erosion?

Soil characteristics, climate, slope, and type of vegetation. Signup and view all the answers

What is the Global Soil Regions?

The worldwide distribution of the Soil Taxonomy's 12 soil orders influenced by climatic conditions. Signup and view all the answers

How have human activities affected the rate of soil erosion?

Windbreaks, terracing, and plowing along the contours of hills are methods to conserve soil. Signup and view all the answers

What are two detrimental effects of soil erosion aside from the loss of topsoil?

Sedimentation and chemical pollution. Signup and view all the answers

Do we see the formation of some ore as the result of weathering?

Yes, secondary enrichment occurs during chemical weathering. Signup and view all the answers

Define horizon.

A layer in a soil profile. Signup and view all the answers

What is soil texture?

The relative proportions of clay, silt, and sand in soil. Signup and view all the answers

What is a soil profile?

A vertical section through a soil showing its succession of horizons and the underlying parent material. Signup and view all the answers

What is the difference between erosion and weathering?

Erosion involves the incorporation and transportation of material, while weathering refers to the disintegration and decomposition of rock. Signup and view all the answers

Other than water, what is a necessary factor for soils to form?

Parent material. Signup and view all the answers

What effects have man's activity had on soil erosion?

Man-made activities like farming, logging, and construction accelerate erosion. Signup and view all the answers

Study Notes

Soil as an Interface

Soil represents a boundary where the solid earth, atmosphere, hydrosphere, and biosphere interact.

Components of Soil

Consists of 45% mineral matter, 25% air, 25% water, and 5% organic matter.

Regolith vs. Soil

Regolith is the layer of weathered rock and mineral fragments covering Earth's surface; soil specifically supports plant growth.

Texture and Grain Size

Sand has larger, coarser grains, while clay comprises smaller, finer particles.

Importance of Soil Texture

Texture significantly affects soil's ability to retain and transmit water and air, which are crucial for plant growth.

Loam Definition

Loam is a balanced mixture of sand, silt, and clay, ideal for nutrient retention and moisture.

Soil Structure

Describes the arrangement of soil particles; platy and spheroidal structures slow nutrient movement; prismatic and blocky structures allow moderate water infiltration.

Controls of Soil Formation

Factors include climate, organisms, parent material, topography, and time.

Soil-Forming Processes

Operate primarily from the surface downwards, impacting layer development over time.

Soil Horizons in Temperate Regions

Temperate regions feature five horizons: O (organic), A (topsoil), E (eluviation), B (illuviation), and C (parent material).

Composition of Soil Layers

Topsoil consist of O and A horizons; the solum includes O, A, E, and B horizons, also called true soil, while the subsoil is primarily the B horizon.

Soil Formation Features

Eluviation is the leaching out of materials; zone of accumulation refers to deposits in the B horizon; hardpan forms from compacted clay layers.

Purpose of Soil Classification

Soil Taxonomy categorizes soils based on their physical and chemical properties for understanding and analysis in contexts like agriculture.

Soil Taxonomy System

Features 12 named soils organized into six hierarchical categories; names derived from Latin and Greek; useful for agriculture, not engineering evaluations.

Soil Erosion

A natural process where water and wind transport soil components, resulting in potential displacement of topsoil.

Factors Influencing Soil Erosion Rate

Influenced by soil characteristics, climate, slope angle, and type of vegetation.

Global Soil Regions

Reference to worldwide distribution of 12 soil orders, shaped by climatic influences, with poorly developed soils at higher latitudes.

Human Impact on Soil Erosion

Practices like windbreaks, terracing, contour plowing, and crop rotation are used to mitigate erosion effects.

Detrimental Effects of Soil Erosion

Sedimentation can lead to reservoir capacity loss and costly dredging; chemical pollution affects water quality.

Ore Formation through Weathering

Secondary enrichment occurs via chemical weathering, where desirable minerals are concentrated in lower zones; examples include bauxite for aluminum.

Horizon Definition

A specific layer within a soil profile.

Soil Texture Explanation

Defined by the proportion of clay, silt, and sand, significantly impacting water retention and air transmission.

Soil Profile Description

A vertical cross-section displaying different soil horizons and the parent material.

Erosion vs. Weathering

Erosion involves material transport by agents like water or wind, while weathering is the breakdown and decomposition of rocks.

Factors Necessary for Soil Formation

Requires parent material, time, climate, and organic contributions from plants and animals; topography affects soil development.

Human Activity and Soil Erosion

Common activities like farming and logging accelerate erosion, leading to sedimentation in waterways and contamination of water supplies.

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Description

This quiz explores the fundamental components and characteristics of soil, including its texture, structure, and the differences between regolith and soil. Understand the importance of soil in supporting plant growth and its interaction with various earth systems.