Glossary - Fundamentals of the Physical Environment - page 899

Morphogenesis The conversion of weathered regolith into a soil profile by processes of
soil formation.
Morphogenetic Said of a geographical region or process where climate is believed to
have created a distinct suite of landforms.
Morphological system A type of system in which the morphological expression is
examined rather than the dynamics of interactions and flows.
Morphotectonic landform A landform created by tectonic processes, such as an island
arc , orogen , rift valley or passive margin coast or any of their principal components.
Morphotectonics The construction of large-scale surface landforms by tectonic
processes.
Mosaic theory The theory of climax vegetation which emphasizes the mosaic patterning
of the climax cover.
Moulin A cylindrical, supraglacial 'pothole' marking the englacial transfer of a surface
meltwater stream.
Mountain circulation winds A general regional pattern of wind circulation determined
or modified by the insolational and mechanical character of mountainous terrain.
Mud flow The moderate to fast downslope movement of a fluidized mass of very fine
debris, or its resultant landform.
Mull Well decomposed and well humified organic matter, thoroughly mixed with
mineral soil by earthworms.
Nappe A fold which has experienced such intense deformation as to have become
recumbent (horizontal) and sheared along its axis.
Natural fire A fire ignited by natural means (e.g. lightning).
Neap tide The twice-monthly tidal period when the gravitational pull of sun and moon
are opposed (at right-angles to each other) and minimize tidal range.
Nearshore The zone of shoreline-wave interaction, subdivided landwards into breaking
wave , surf and swash zones.
Negative feedback A feedback effect in which the initial change in the system is damped
down.
Neotectonic Plate tectonic activity during the late Cenozoic era.
Net ecosystem production ( NEP ) The change in the biomass of an ecosystem per unit
time; equivalent to net primary productivity minus losses due to grazing by herbivores.
Net primary productivity ( NPP ) The amount of energy fixed by plant photosynthesis ,
taking losses by respiration into account; it represents growth by the plant or
ecosystem, and is measured per unit area per unit time.
Net radiation The difference between the total incoming and outgoing radiation terms. A
positive value would indicate greater incoming than outgoing energy and so a
warming; a negative value would indicate the reverse.
Net radiation deficit The situation in which Earth is losing more radiant energy than it
is gaining.
Nitrate - vulnerable Zone ( NVZ ) An area where there are restrictions on the use of
nitrogen fertilizers.
Nitrification The conversion of organic nitrogen compounds in soil organic matter into
nitrates by soil micro-organisms.
Nitrogen fixation The conversion of atmospheric nitrogen into organic nitrogen
compounds by soil microorganisms, either free-living or in nodules of plant roots.