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Quick review for G107
Physical Geography Part III
Draft
Part III
Draft by Isiorho. June 4, 2001
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Soil
 ‘And the Lord God formed man (woman) of dust (soil)
from the ground..and out of the ground the Lord God
formed every beast..bird’
 Soil:
definitions… depends on the field
 Soil is the upper layer(s) of the earth in
which fine rock particles and organic
material provide the basis for plant life
(inorganic + organic + living things)
Draft by Isiorho. June 4, 2001
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Why different Soils
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Five major environmental factors in soil
formation
 S = f(CROP)T
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S = soil
F = function
C = climate
R = relief (topography)
O = organism (plants & animals)
P = parent materials
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Soil profile
 Layers/colors
in soil = soil profile
 Pedon = 3-D representation of soil
Draft by Isiorho. June 4, 2001
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Soil Horizons
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Soil Profile
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Divided into three zones or horizons
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O- accumulation of decaying matter (included in A
horizon)
A- zone of Eluviations
B- zone of Illuviation
C- transition zone between solum or true soil and parent
material
Solum or true soil is made up of A & B horizons
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Soil Properties
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Color – black, gray, brown, yellow, blue, green, red, white
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Black indicates the presence of organic (humic) matter i.e.
fertile soil
Red indicates the presence of iron compounds
Texture
Size of individual grains:
 gravel, sand, silt and clay
 (gravel is not considered here)
 loamy soil, silty clay,
clayey sand
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Soil Properties
 Structure
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Crumpy, granular,
blocky, columnar,
prismatic, and platy
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Soil Properties
 Chemistry
 pH,
Base ions (base cations)
 Ca, Mg, K, Na clay minerals- illite, kaolinite,
montmorillonite
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Pedogenic Regimes
 Laterization
(ferralitization)
 Podzolization
 Gleization
 Calcification
 Salinization
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Soil Classification
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Soil Orders
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Oxisols – heavy leaching… equatorial/tropics
Ultosols- clay accumulation… equatorial/tropics
Vertisols.. Tropics/subtropics
Alfisols.. Accumulation of clay… subhumids
Spodosols- cold moist climates
Mollisols- subhumid- semiarid..chernozem..prairie
Aridisols- dry climates
Histosols- large accumulation of organic… bog
soil
Entisols- lack soil horizon
Inceptisols- some weakly developed soil horizon
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The Earth

Divided into three major layers
 Crust- continental crust (Sial)(lighter than
oceanic crust) and Oceanic (Sima) crust with
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Mantle
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Crust plus upper mantle = lithosphere
Boundary between crust and mantle =
Mohorovicic Discontinuity (MOHO)
Lower (plastic) part of upper mantle =
Asthenosphere
Core
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Plate Tectonic

Lithosphere = crust and upper mantle
 Asthenosphere = the semi-liquid part of upper
mantle
 Lithosphere broken into large pieces called
PLATES
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Three types of plate boundaries
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Divergent
Convergent
Transform
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Composition of the Crust
 Eight
elements (oxygen (47%), silicon
(28%) aluminum, iron, calcium, sodium,
potassium and magnesium) form the
bulk of the minerals in the crust.
 There are over 3000 known minerals
A
mineral is a natural occurring substance
that is inorganic, has definite chemical
composition, and is crystalline
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Group of Minerals
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Silicate- most important group- examples
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Quartz, feldspar (orthoclase, plagioclase), Mica
(Biotite & Muscovite), amphibole, pyroxene, olivine
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Carbonate- calcite
 Sulfides- galena & pyrite
 Sulfates- gypsum
 Oxides- hematite
 Phosphate- apatite
 Halides- halite
 Natives- sulfur, copper, silver, gold
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Mineral Physical characteristic
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Color
 Streak
 Luster
 Hardness
 Crystalline form
 Fracture
 Cleavage
 Others- striations, smell, odor etc.
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Rocks
 Rocks
are aggregation of minerals,
usually made of two or more minerals.
 Three
Rock Groups
 Igneous
 Metamorphic
 Sedimentary
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Igneous Rocks

Igneous rocks are rocks that form from
molten material = magma
 The molten rock is magma when it is still
within the earth and Lava when it exposed on
the earth’s surface
 Intrusive and extrusive
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Can tell them apart using Texture (Phaneritic
(visible with naked eye) and Aphanitic)
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Igneous Rocks Contd.
 Examples
 Granite,
of Intrusive igneous rocks
Diorite, Gabbro, Pegmatite
 Examples
of Extrusive Igneous Rocks
 Rhyolite,
Andesite, Basalt, Obsidian,
Pumice Scoria
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Plutonic Rocks
 Intrusive
igneous rocks classified based
on size, depth of formation and
relationship to surrounding rocks
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Metamorphic Rocks

These are rocks that form as a result of
alteration of existing rock due to high
temperature and or pressure
 Two types of Metamorphic Rocks
 Non foliated and Foliated
 Nonfoliated metamorphic rocks include
quartzite, marble, anthracite coal
 Foliation is the alignment of minerals
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Examples of foliated met. Rocks- slate, schist,
phyllite, gneiss
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Sedimentary Rocks
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Produced from broken pieces of rocks or
precipitates or
 Lithification id the process whereby individual
sediments are turned into solid rocks
 Types of sedimentary rocks- clastic (detrital)
& biochemical
 Examples of sedimentary rocks- sandstone,
conglomerate, breccia, siltstone, mudstone,
shale, limestone, rock salt, bituminous coal
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Weathering and Mass Wasting
 Weathering
is the breakdown of rock or
chemical decomposition of rock, thus
two types of weathering: Physical
(Mechanical) and Chemical
 Physical
 Chemical
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Physical weathering
 Frost
action
 Salt action
 Unloading
 Plants
 Animals
 Heating & Cooling cycles (thermal)
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Chemical weathering
 Other
than the rock itself, water is the
most important substance needed for
chemical weathering
 Hydration
 Hydrolysis
 carbonic
 Solution
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Mass Wasting

The downward movement of earth material
under the influence of gravity
 Classified based on material type, velocity,
water content
 Types of Mass Wasting
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Fall…
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Flow……just like a river
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Slump…this is what kids do in the park
…remaining intact as shown in the diagram
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Slide…rolling (turn over) …
Creep- this occurs imperceptibly
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Expanded Key Words & Phrases

Soil horizons, base cations, leaching, eluviations,
Illuviation, soil colors and their meaning,
pedogenic regimes or soil forming processes,
minerals, rocks, plate boundaries, chemical
weathering, mechanical weathering, karst terrain,
plate tectonic, lithosphere, Sial (Continental
crust) & Sima (Oceanic crust) with Sial being
denser than sima, asthenosphere, Mohorovicic
Dicontinuity (MOHO) the boundary between
crust and mantle, Weathering (Physical
(mechanical) & Chemical), climates favorable to
physical weathering and chemical weathering,
mass wasting…types and being able to identify
them given drawing
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