PLSCS 2600 Prelim 1

Dirt

Soil that is out of place

Soil must be thought of as

Volume

Soil is at the interface of

Four realms: Atmosphere, lithosphere, hydrosphere, and biosphere

Soil components

50% solids, 25% solution, and 25% air

Breakdown of solids in soil

45% mineral, 5% organic

Traditional soil surface

Loose, altered surface material of the earth which nourishes and supports

Difference between traditional and geologic definitions of soil

Geologic does not include support of plant life; traditional includes rocks, water, snow, and air

Soil Altering Processes

Additions, Losses, Transformations, and Translocations

Modes of transport for additions

Landslides, floods, winds

Functions of soil

Medium for plant growth, recycle system for nutrients, habitat for soil organisms, engineering mediums, and watter supply

Soil forming equation

S= f(pm, c,t, r, b)

How does climate impact the soil function?

As temperature increases, biological activity increases; in addition, as moisture increases, biological activity increases until H20 doesn't have enough O2 for aerobic organisms

Pedon, polyypedon, landscape

Individual unit, units that are the same, and multiply polypedons

Glacier formation

Cold air hitting sea, evapotranspiration, moist air, snow , accumulation

Mountain glaciers

Form on top of mountain; flow downhill and carve out

Terminal moraine

Glacially formed accumulation of glacial debris

V shape v U shape when looking at landscape?

Carved by streams v. glaciers

How to tell if glacier was moving North to South versus East to West?

Carved out v. filled in (water pushing debris out with hanging valley in back)

Drumlin

Ice has imperfections from rocks, so has highs and lows as ice moves over (pockets) that are tear-shaped

Esker

Pile of rocks in any direction (ribbons)

Soil architecture

Texture, structure, bulk density

Particle size

Stones and pebbles are largest; fine-earth fraction includes sand (2mm), silt (0.002mm to 0.05mm), and clay

Particle size matters due to

Surface area

Loam

Intermediate between clay and sand

Sand: sorting and packing

Well-sorted, loose packing

Silt: Grade, packing

Well-graded, loose packing

Clay: Sort, Packing

Well-sorted, tight packing

Aggregate

Clumps of particle

Micropores v macropores

Smaller particles with capillary action

Act as big and small straws (much more draw)

Soil structure

Spheroidal/granular, plate-like, prism-like, block-life, massive

Prism-like

Columnar or prismatic

Block-like

Angular or subangular blocky

Granular

Cookie crumbs

Blocky

Irregular blocks

Prismatic

Vertical columns of soil that might be a number of cm long. Usually found in lower horizons

Columnar

Vertical columns of soil that have a salt cap at the top

Platy

Flat plates of soil that lie horizontally (compacted)

Single-grained

Soil is broken

Drainage classes for structure

Rapid for granular/single grain, moderate for prismatic/blocky, and slow for massive and platy

Pro/con of small pores

Hold water well but restrict aeration

Pro/con of larger pores

Permit free air flow but hold water poorly

Soil as a three-phase system

Soil air (connection to atmosphere), soil solution (solvent for reactions), and soil solids (reservoir of nutrients)

A horizon

Topsoil (partially decomposed)

E horizon

Zone of leaching, lighter in color, restiant materials

B horizon

Accumulation

Eluviation

Clay and iron oxide lost

Illuviation

Clay and iron oxide gained

Solum

O-B horizons

Where/ where aren't O horizons

Forests, agricultural fields

Bh, Bs horizons

Humus and sesquiodies, cool/humid climate, coarse parent material

Bf

Clay illuviation with moist climate

Bk horizon

Carbonate, arid/semi-arid climate

bulk density

The mass of dry soil per unit volume

What is key to keep in mind with bulk density?

If too high, roots can't penetrate

What soil transformation are organic matter (deposition of plant material), solutes (salts introduced by groundwater), and sediment (aerial and fluvial deposits)?

Additions

Examples of losses

Sediments (erosion), solutes (leaching by groundwater), OM (oxidation)

Examples of transformation

Mineral altercations, recrystalization from weather products, salts through capillary action?

The steeper the environment, the more

Change

Examples of parent material

Organic deposits, mineral deposits (chemical/physical weathering that are usually transported)

Direct effects in relation to parent material are

Inherited

Examples of inherited effects from parent material

Rocks, unconsolidated material (soil is sandy but was transported)

Rocks are

Indurated or consolidated material

Types of rocks

igneous, sedimentary, metamorphic

Examples of indirect effects

Acquired (e.g. weathering)

Difference between chemical and physical weathering

Chemical alters composition, physical just makes smaller

Alluvial

Parent material transported by water and transported in streams

Lacustrine

Parent material transported by water and deposited in lakes

Parent material transported by gravity

Colluvial

How does surface area affect weathering?

More SA = more weathering

How does climate affect soil?

Precipitation and temperature

What is the main agent of weathering

Water

Clay formation

Most rapid at high rainfall levels due to more water meaning more reactions

C:10 rule but what to keep in mind

As temperature increases, so does reaction rate. BUT if wet, not enough oxygen to decompose

Why are temperature changes less drastic in deeper horizons?

Earth acts as insulator

Bioturbation

Plants and animals mix surface organic matter into subsurface

What does relief determine?

Effective v. actual precipitation

Where are deeper/shallower soils with mountain

Depper where C/10 rule, more soil genesis

How to measure time with soil?

Carbon dating, volcanic ash layers

Difference between soil forming factors and soil forming processes

Factors are the conditions from which soil is formed; the processes are what act on the factors

What are the soil forming factors?

Additions, losses, translocation, and transformation

What is translocation primarily due to?

Gradients in water potential and chemical concentrations within soil pores

What may move due to translocation?

Solube minerals, colloidal material, organic compounds, iron

Three most abundant elements in earth's crust

Oxygen, silicon, and aluminum

How is sandstone made up?

Oxygen atom + silicon atom, silica tetrahedron, quartz crystal, grain of quartz, sandstone rock, and sandstone outcrop

Soils as stage in geologic cycle

Parent material in-place (residual) or transported, surficial processes (climate, wind), subduction, magma, cooling, uplift, exposed rock

Igenous rock

Extrusive v intrusive

Extrusive igneous rock

Magma cooled at surface (lava flow) and produces small crystals

Intrusive igneous rock

Magma cooled below surface (produces large crystals with different rates of crystallization per mineral type)

Sialic rock

Mostly quartz and K-feldspars that are resistant to weathering (igneous)

Malic rock

Contains less quartz and more MG, Fe-rich minerals; not resistant to chemical weathering

Which igneous rock is more resistant to chemical weathering

Sialic instead of mafic

Types of sedimentary rocks

Conglomerate, Sandstone, siltstone, shale, limestone

Conglomerate rock

Gravel

Limestone

Carbonaceous shale

Are sedimentary rocks or igenous more porous/softer?

Sedimentary

Types of metamorphic rock: limestone, shale, granite, sandstone

Marble, slate, gneiss, quartzile

How are metamorphic rocks formed?

Heat and pressure

Rock consolidation v. weathering: Hard, soft, unconsolidated

Slow, faster, fast

How does mineralogy impact soils?

Influence secondary mineral formation, soil fertility, nutrients