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Chapter 7

Chapter 7 Weathering.docx

Course Code
GEOG 1300
John Lindsay

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Chapter 7: Weathering
7.1 Introduction
Geomaterials this is the cumulative name given to rocks and regoliths, materials which are
derived from a geologic source
Regolith (s) the basal layer of soil overlying the bedrock composed of loose, unconsolidated
weathered rock and gravel debris; it is the raw material from which soils are developed
Metamorphism (metamorphosis) (biological) a change in the form, function or habits of a
living organism by a natural process of growth or development
7.2 Environmental and material controls on weathering
Photochemical oxidation a process which occurs in the presence of light and results in the
chemical change of a substance through the loss of electrons
7.3 Some fundamental processes
Sub-aerial an object or a process which exists or occurs near or on the surface of the Earth
Reagent a substance or compound which is added to another substance to initiate a chemical
reaction or to determine whether a reaction will occur
Electrons within an atom electrons are the negatively charged particles
Solvent a substance which dissolves another substance to produce a solution
Alkaline a substance which has properties of an alkali, a pH greater than 7
Base pertaining to substances with a pH above 7 or substances that release hydroxide ions
Cations positively charged ions
Valent a substance which has valence, often used to refer to the potential of an atom to
combine with another atom. This is dependent on the number of atoms which can be shared,
lost or gained through combining
Surface tension the resistance of the surface of a material to external forces. It is determined
by the cohesive energy between the molecules which form the surface of the object. Molecules
in the middle of an object are subject to equal forces on all sides whereas forces acting on the
surface molecules are not in balance
Capillarity also known as capillary action. It is the process whereby a liquid can act against the
force of gravity and flow upwards in a narrow tube such as those found in a porous material. It is
dependent upon the surface tension of the liquid and the adhesion of the molecules
Absorption the action of removing and carrying away a superficial material; it primarily relates
to the sublimation, melting and evaporation which remove snow and ice from the surface of a
glacier or snowfield. It can also be applied to the wearing away of rock by water and the removal
of salt or sand from a surface by the action of wind
Hydrates a compound which contains water but which can dissociate into water and another
compound. This process is reversible and therefore the compound and the water can combine
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