Glossary - Fundamentals of the Physical Environment - page 737

fatigue failure is apparently most effective in a moist
environment.
Intact rock-mass strength The peak strength of a rock
mass capable of resisting shear; Mohr-Coulomb criteria
define it as comprising internal cohesion, friction strength
and normal stress.
Interception The process which catches and stores
precipitation in a vegetation layer, where it may be used,
evaporated or transmitted on towards the ground.
Internal deformation The change of shape and volume
of a mass of Earth material due to a change in the nature
or arrangement of its internal properties; a process by
which material moves under its own mass.
Interspecific competition

Joint A fracture between the constituent parts of a rock
mass, usually caused by its contraction on cooling or
drying.
Jökulhlaup A flash flood of glacier meltwater from a
subglacial or glacier-margin lake due to failure of an ice
dam.
Kame A steep, isolated mound of glaciofluvial sand and
gravel deposited in contact with glacier ice.
Kame moraine An irregular ridge of glaciofluvial
sediments marking a glacier terminus, formed either by
the wholesale meltwater reworking of a moraine or the
coalescence of kames and kame terrace fragments.
Kame terrace A valley-side bench of glaciofluvial sedi-
ment marking the course of an ice-marginal meltwater
stream.
Kaolinite A 1 : 1 type of clay mineral of high stability but
little reactivity, composed of a silica sheet fused with one
alumina sheet.
Karst geomorphology A landsystem uniquely developed
on carbonate rocks by the predominance of solution and
the progressive development of underground drainage.
Katabat The outflowing, descending portion of a local
thermal circulation system during the cooling phase of
diurnal heating in a mountainous region, or any other
more general cold air drainage current.
Katamorphism Intense and rapid weathering of rocks by
hydrolysis, hydration and oxidation under humid tropical
conditions.
Keystone species Species whose presence or absence in
an ecosystem has a dominant effect on productivity,
composition and biodiversity.
Kind A property of soil structure referring to the shape
of the aggregates.
Kinetic energy The energy possessed by a body because
of its movement. Its magnitude is equal to 1⁄2 mv 2 ,where
m is the mass of the body and v is its velocity.
Klippe A fragment of a nappe dispersed away from its
source into the mass of a collision orogen .
Knick point A step in the long profile of a stream
marking the rejuvenation of fluvial incision after uplift.
Knock-and-lochan A highly abraded, rocky land surface
characterized by streamlined ridges and intervening
basins, usually of glacial origin.
Krummholz A woodland of dwarf trees marginal to the
timberline, whose individuals are severely stunted by cold
and wind pruning.
Kuroshio The warm, north-east-flowing current of the
clockwise gyre in the north Pacific Ocean, flowing from
the Philippine coast and deflected southwards in the
eastern Pacific by the Alaskan coast.

Competition between distinct

species.
Interstitial ice Individual or fused ice crystals occupying
the voids of a soil or rock.
Intertidal zone The zone lying between low-water and
high-water marks which fluctuates in width and height
range with the monthly tidal cycle.
Intraspecific competition Competition between individ-

uals of the same species.
Intrazonal A class of soils whose profiles are dominated
by local factors (e.g. geology, topography).
Intrusion An igneous rock mass of intrusive origin
forming a subsurface batholith , dyke , pluton or sill and
exposed at the land surface only by subsequent erosion.
Intrusive A description of molten igneous material
which penetrates surrounding rock and cools and
solidifies before reaching Earth's surface.
Ion An atom which has lost or gained one or more
negatively charged electrons.
Ion antagonism The blocking of the uptake of one
cation by the presence in excess of another (e.g. excess
calcium inhibiting iron uptake).
Ionic substitution The replacement of one or more ions
in a crystal structure by ions of similar size and charge,
without altering the crystal structure.
Island arc A narrow belt of intense seismovolcanic
activity, containing arcs of active volcanoes flanked by an
outer ocean trench and inner marine basin, marking the
surface expression of a B-subduction zone.
Isomorphous substitution The replacement of one atom
by another of similar size in the crystal structure of clay
minerals, without disrupting the structure.
Isostasy The equilibrium condition in which lighter crust
'floats' on denser mantle and whose relative proportions
from one place to another maintain Earth's shape.
Isostatic adjustment The vertical and lateral displace-
ment of crust and lithosphere in order to maintain or
restore isostatic equilibrium.