Welcome to the 2004 Massachusetts Envirothon Workshop

Soils Overview Workshop

Part ITom Cochran

USDA-NRCS Franklin Co., MA

Some material courtesy of Jim Turenne

USDA-NRCS, Rhode Island

Road Map

We will begin with a definition of soil.

The five soil forming factors will be discussed in the following order

Parent material, Climate, Organisms, Topography, and Time

Discuss the formation of horizons and their characteristics

Discuss soil texture, structure, and color

Discuss redoximorphic features, and drainage class

Discuss soil interpretations from a soil survey

Soil Definitions

1) The unconsolidated organic and mineral material on the earth’s surface that is capable of supporting plants.

(MA Envirothon Team Resource Manual)

2) A dynamic natural body, in which plants grow, that is composed of mineral and organic materials and living organisms. (Brady & Weil, 11th Ed.)

Components of Soil

Mineral materials = boulder, stone, cobble, gravel, sand, silt, and/or clay sized particles of gneiss, granite, schist, or slate .

Organic materials = leaf litter, crop residue, decomposing animal bodies, and compost.

Living organisms = plant roots, earthworms, nematodes, fungus, bacteria colonies

Five soil forming factors

1) Parent material : Rocks

2) Climate : Precipitation, Temperature changes

3) Organisms : Bacterial and fungal colonies, worms, rodents

4) Topography : Slope, Landscape position

5) Time : How long climate has been altering parent material geologic time

Parent materialIn the Appalachian Mts., granite, gneiss, schist, and slate represent the geology of the parent material. Organic soil material forms from decaying carbon life forms. Coastal areas are underlain with ocean sedimentary material.

Each of these materials produce distinctive groups of particles from the weathering process.

Climatic & glacial forces break particles from the rock surfaces, forming boulders, stones, cobbles, and gravel, which are called fragments. sand, silt, and clay.

Parent material (continued)

Parent material can be

rocks weathered in place (residuum)

Or mineral material deposited by

water (alluvium)

wind (eolian)

gravity (colluvium)

lake bed sedimentation (lacustrine)

ocean deposits (marine sediment)

glacial deposits (till)

Or organic material

Glacial processes have determined the parent material in much of New England.

• Appalachian Mtns were created by continental plate shifting and associated geologic activity, millions of years ago.

• Ice covered Massachusetts 12 – 14,000 yrs ago. Ice forces reduced the mountains to various types of till, which was deposited on the earth’s surface, leaving glaciated parent material.

• Major types of glaciated parent material include

• Basal till – formed under the pressure of thick ice, which packed the particles tightly together.

• Ablation till - loose, permeable till deposited during the final down-wasting of glacial ice.

• Glacial outwash – parent material deposited by glacial melt water as the glaciers receded.

• Glaciolacustrine deposits - parent material deposited by particles settling in glacial lakes

Ice

Lake

Till

Outwash

Courtesy of Jim Turenne

Glacial Till

Unsorted/stratified material deposited beneath and within glacial ice.

Heterogeneous mixture of all particle sizes (boulder to clay).

Oldest surficial deposit overlying most bedrock areas.

Paxton seriesMass. State soil

Bedrock-controlled areas

In areas where till deposits are thin bedrock is seen at the surface and within the soil profile.

Parent material above bedrock is still glacial till.

Glacio-fluvial Parent Glacio-fluvial Parent MaterialsMaterials

Glacial Outwash

Dominantly sand and gravel sized particles.

Rapid water movement, associated with aquifers.

Few limitations for most uses.

Glacial Lacustrine/Marine

Generally fine textured sediments deposited in glacial lakes with the sediments now exposed to the surface.

Large areas often well identified (Taunton, Hitchcock, Sudbury).