Midterm One Flashcards
What is Pedology?
The study of natural bodies according to their origins, properties and classification.
Define Soil
A collection of natural bodies occupying portions of earth’s crust, capable of supporting plant life.
What are the 5 factors creating soil properties?
hint: clorpt
Climate, Vegetation + Organisms, acting on Parent Material, as conditioned by Relief, over periods of Time
S= f (cl, o, r, p, t)
What is the upper boundary of soil?
air
What is the lateral boundary of soil?
H2O bodies + rock outcrops
What is the lower boundary of soil?
rock/hard material
Define Pedon
The smallest 3D structure at the surface that is considered as soils.
Define Soil Horizon
A layer of soil approx. parallel to the surface and differs from other horizons in the soil profile
Define Landscape
a collection of 1 or more landforms
Define the O Horizon
Organic layers at the surface of the organic soils - not in all soil, only organic
Describe the A Horizon
layers nearest the surface, dominated by mineral particles, darkened by OM, has the most intense biological activity
Describe the Ae Horizon
intensely weathered + leached, has NOT accumulated OM.
e=eluviated
Describe the B horizon
less OM, has prominent silicate clays and oxides (secondary minerals), washed away from above or formed in situ by weathering
Describe the C horizon
mineral horizons below solum, least weathered
aka parent material - developed first
What are 5 ecological roles of the functions of soil?
- medium for plant growth
- recycling system of nutrients + wastes
- habitat ofr soil organisms
- engineering medium
- system for H20 supply + purification
What is the origin of soil?
non-soil material called rocks + vegetative material in bogs
What is the creation path of soil? (sequence)
rocks –> regolith –> parents material –> mature soil
Why does weathering occur more intensely on the surface?
rocks at depths are at equilibrium with their environment therefore there are no further changes. rocks are not at equilibrium with their environment on the surface
What is Pedogenesis?
all physical, chemical and biological alternations that give rise to different soils
What is Diagenesis?
all physical + chemical alterations that occur to rocks. Occur on primary rocks to get secondary rocks.
What are the 4 types of process surface rocks undergo during genesis?
- Addition to materials
- Subtraction of materials (breakdown)
- Movement within soil (translocation)
- Transformation from one mineral to another (chemical), change in size/formation
Define weathering
the action of the atmosphere, hydrosphere and biosphere on the surface of the lithosphere.
Define Landforms
Configurations of the land surfaces taking distinctive forms, produce by natural and/or un-natural processes.
Two types: Initial and Sequential
Define Initial Landforms - Primary
produced by internal (endogenic) earth forces
-such as tectonic activity, volcanoes, flat scarp
Define Sequential Landforms - Secondary
produced by external (exogenic) earth forces which cause denudation (lowering of the landscape), create depositional products
-sandbars, moraines, talus cones
What are some facts that determine the rate of weathering?
- Climate
- governs intensity of phys, chem, + bio. - Physical + Chemical Properties of the Rock
- harness particle size, solubility +crustalline
3 Classifications of Rocks based on mode of formation
- Igneous (plutonic) rocks - magma
- Sedimentary rock - deposited
- Metamorphic rocks - through metamorphosis
Define Rocks
Inorganic soil substances composed of one or more minerals
Define Igneous
formed from solidification
- contains many primary minerals
- either extrusive or intrusive depending on whether it was formed on the outside or inside of the earth
Define Sedimentary
from deposition + recrystallization of weathering products from other primary and secondary rocks
Describe Physical Weathering
non-chemical reactions on rock that lead to a change in size
Describe Chemical Weathering
When chemical species cause a change in size and chemical composition
Monomineralic Rock
has only one type of mineral
What are 4 agents that transport PM?
1) Gravity
2) Water
3) Ice
4) Wind
What classification do we use to report soil colour?
Munsell colour notation
Define Hue
Dominant spectral solour
B, G, R, Y + intermediates
Define Value
Relative lightness/darkness of spectral colour
ranged 0-10
Define Chroma
Relative purity of spectral colour
Aggregates/peds
compound particles, very small
- separated by applying pressure to lines of weakness
- secondary compound particles in coherent shape
Soil Structure
The arrangement of primary particles into larger secondary particles separated by lines of weakness
Structure less
Massive
no coherent shapes
- very sandy soils
- very clayey soils (clods/hard clumps when dry)
Define the Grade of a structure
strong, moderate, weak
Define the Class of a structure
coarse, medium, fine
Define the Kind or Type of a structure
shape + degree of roundness of peds
Flocculating
process by which individual particles of clay aggregate into clotlike masses or precipitate into small lumps
-Ca2+ ions
Cementing
the stable domains of clay are formed by flocculation and OM then they act as cementing agents
Granular
rounded with a few sharp edges
Crumb
some granular but porour
Blocky
mainly sharp edges
Subangular Blocky
some edges have been rounded
Platy
wider than it is tall
Prismatic
Taller than it is wide
Columnar
taller than it is wide but tops are rounded
