Transcript Soils Overview Part 1 - Massachusetts Envirothon

Welcome to the 2004 Massachusetts
Envirothon Workshop
Soils Overview Workshop
Part I
Tom 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 material
In 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 series
Mass. 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
Materials
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).