Geoscience Reference
In-Depth Information
Fault
A line or zone along which
faulting
has occurred
in rock mass.
Fault breccia
Angular rock rubble lining a fault and
formed by shearing and crushing of a wider zone of rock
mass bounding the fault during movement.
Faulting
The process of fracture or brittle failure of rock
with displacement of adjacent parts on either side of the
fault
.
Feedback
The property of a system such that, when
change is introduced via one of the variables in the system,
its transmission through the system leads back to a change
in the original variable.
Felsenmeer
A German term for
blockfield
.
Felsic
A mnenomic from
fel
dspar and
si
li
c
ate, which
identifies the silicate-rich igneous rocks characterized by
their light-coloured, acidic minerals.
Fetch
The extent of open water over which a dominant
wind develops a wave system.
Field capacity
The maximum volume of water held in
the voids of a soil when gravitational drainage is complete,
comprised of
capillary
and
hygroscopic
water.
Firn
A stage in the transformation of snowpack towards
glacial ice, with a density of 0·4-0·5
Fluid stressing
The erosive power of a stream contri-
buted by fluid shear stress at the stream bed.
Flysch
Submarine
turbidite
sediments eroded from an
orogenic belt during uplift and therefore located in
adjacent
trench
or
back-arc
zones.
Föhn
An equivalent of
the chinook wind in the
European Alps.
Fold
A compressional or gravitational plastic deforma-
tion of Earth materials which has bent and shortened a
previously planar mass.
Foliation
A close-spaced planar texture in rock acquired
by the alignment of platy minerals during
metamorphism
.
Force
Mass
acceleration measured in newtons, N (SI
units).
Fore arc
A zone lying between and parallel to the trench
and
volcanic arc
of a
B-subduction
zone, consisting of an
outer ridge and an inner basin.
Fore-arc basin
A narrow marine basin lying just offshore
of a volcanic
island
arc in a
B-subduction zone
.
Foreshore
That part of a beach lying between the low-
water mark and maximum high-tide mark.
Formation
A world vegetation type dominated by plants
of similar life form and identified in a geographically
distinct area.
Fossil soil
A soil formed in the past under environ-
mental conditions which no longer exist.
Fractional crystallization
Separation of a
magma
during
cooling into distinctive, usually mineral-specific parts.
Fractionation
10
3
kg m
-3
.
Fissure
A wide fault or tension crack in the land surface
often associated with a linear volcanic eruption.
Fixation
The transformation in soil of a plant nutrient
from an
available
to an unavailable state.
Fjord
A long, deep rock basin excavated by an
outlet
or
valley glacier between high rock walls and flooded by the
sea during deglaciation.
Flandrian stage
The current global
temperate stage
,
more or less synonymous with the Holocene, which
commenced
c.
10,000 years
BP
.
Flexural isostasy
Localized isostatic adjustment
peripheral to, and in an opposite direction from, an area
of crustal loading or unloading; due to flexure or
creep
in
the lithosphere.
Flocculation
The aggregation of individual suspended
clay particles into larger masses, with consequential
implications for their sediment dynamics.
Flood basalt
An extensive basalt flow extruded from
continental rifts and fissures which forms distinctive
terrestrial land surfaces.
Flood plain
A lowland land surface prone to episodic
river floods and associated alluvial sedimentation.
Flow regime
The range of styles of stream flow and
their related
bed forms
and modes of sediment transport.
Flow tuff
A lithified form of volcanic ash which once
moved as a
pyroclastic flow
and contains evidence of that
movement,
The separation of
a mixture into its
component elements and minerals.
Fragipan
A dense pan-like subsoil horizon, indurated by
physical and/or chemical processes, and with a high bulk
density.
Free-living fixation
Fixation of atmospheric nitrogen
into organic nitrogen compounds by soil micro-
organisms which live freely in the soil rather than existing
in association or symbiosis with a plant.
Friction strength
The portion of rock or soil strength
dependent on the frictional contact between constituent
particles.
Frost heave
Process of vertical and lateral movement in
periglacial soils in autumn due to expansion of water into
ice and vein-ice aggradation.
Frost shattering
The fracture of rock mass attributed
to internal stress generated by expansion on freezing,
pore water migration to a freezing plane or hydration
in the
permafrost
environment; it is probable that
some form of
fatigue
is involved over many freeze-thaw
cycles.
Froude number
often in the form of
parallel extruded
An index of the type of flow in a stream.
minerals.