Geographical Terms : Letter F

ened valleys due to a rising sea level after the melting
of the Pleistocene ice-sheets. Fiords show many char­
acteristics of glaciated V-shaped valleys. They are com­mon in Norway, on the Pacific coast of British Columbia, Canada and South Chile.
Fimification Firnification refers to a combination of pro­cesses in which new snow is transformed into glacier ice, owing to the release of air and a change in
crystallography. "

Flash Flood A short-lived but rapid rise of water in a river is called flash flood. The quick and sudden rise of water may be due to snowmelt, heavy rainfall, the collapse of an ice-dam, log-jam or artificial dam.

Flood Flood may be defined as the inundation by water of any' land area not normally covered with water owing to a relatively rapid change of the level of the
particular water body. Floods may Occur due to (i) increase in rainfall, (ii) snowmelt, (iii) rise in water level in lakes, (iv) cyclone, (v) earthquake, and (vi) collapse of dams.

Flood Frequency The term flood frequency refers to a type of data analysis based on flood records in order to determine the probability of flood magnitudes and the
possible recurrence intervals.

Floodplain A floodplain is a low-lying land that borders a river is subjected to periodic flooding. In otrer words, it is that part of a river valley over which a river flows in times of flood. A zone of low relief and gentle gradients, a floodplain is composed of alluvium and - incorporates ox-bow lakes, point bars, abandoned chan­ nels and scrolls.

Florida Current One of the important currents of the North Atlantic Florida current comes as a branch of the north equatorial current which enters the Carribean and then returns to Atlantic Ocean through the Florida Straits as Florida current. Florida current is the southern portion of the Gulf stream.

Fluidisation Fluidisation is defined as the process in which
finely powdered rock material is invaded by an uprising
stream of very hot gas which welds it together and
causes it to flow like a liquid.
Focus (of an Earthquake) The point of origin of an
earthquake within the earth's crust is called the focus
of the earthquake. Focus of an earthquake is also known
as the hypocentre, the seismic focus and the seismic
origin. An earthwake originating (i) at a depth of more
than 300 km is called a deep focus earthquake, (ii) at
a depth of less than 70 km, a shallow focus earthquake,
and (iii) at depths between 70 km and 300 km, an
intermediate focus earthquake.
Fog Fog is defined as droplets of water suspended in the
lower layers of the atmosphere whose visibility is less
than one kilometre. Fogs result from the condensation
of water vapour around the nuclei of floating dust or
sm9k~ pMticles.
Fohn (Fadm, f9n) Fpftn is a warm and dry wind which
descends On the le~Wi"lf9 sid~ pf P Ipountain range,
especially the Alps in EYfQP@, An ifflpprt~1T).t f=h?racteris­
tic of fohn is the rapid rise of temp!'1n~t~f(;? tpM it
generates, generally more thaft 10" C in a fgw pour§:
Fohn is mOst common in I>prfn~ l:Utq autl/mo.
.
Fold Mountains Mountain~ that ' fe formeq )'.u1der com­
pression in which the sedimentary rock stra'ta are
squeezed into a succession of synclines and anticlines,
are c~lled fold mountains. Fold mo~ntain~ represr,nt ~p
upland area formed by the buckling of earth's crust:
Foli~tion The term foliation refers to a laminated or banded
" , ".' I'"'' ,1! ,) '". '"
structure within a' metamorphic rock. Such a structure
is caused by the segregation of diffbrent minerals into
parallef layers due to' schistosity of th~ r~c~. Fpl~a,tipn
is also defined as the stratiform structure of ice in the
lower layers of a glacier. '
Fossil Fossils are the remains of a plant or animal preserved
i~ .sediment~ry rock. Rocks. of ~ s~miiar a~e apq ~H~f,°­
slhonal envIronment possess sImifar fOSS"Ils.
Front A front is ~terin usecfto describ~ a sloping boundary
piarie or surface separating...t.o air masses that exhibit
different meteorojogical properties or characteristics. It
was formerly used for the tropics to describe the ITCZ
but the usage is now restricted to higher latitudes where
thermal discontinuties are much more pronounced.
A cold front is the front that separates a retreating warm
air mass and an advancing cold air mass, which forces
its way underneath "the warm air causing ittq ri'se.
Conversefy, a war~ front !~ the fr~nt that s~.R~f.at~~ 'I
retre~ti~& cold air ina~s 'i'\!ld an advancing warm air
mass:,LWhich rises above the cold air. A cold front is
steeper than a warm front and the weath~r a,ssociated
with it tends to pass more rapidly.
Frost Frost refers to a' weather condition that occurs when
, ,', ' Ie,. :'
the air temperature is at or b~low 0 "~. ~t is "Iso p~fjl1ed
as a weathering agent which ~reak~ up rocks ami (>QH
owing to freezing of the inte.rsfitial water:'" . L' '"
Fuller's Earth A fine earth similar to a cla~ bl.~t lacking
plasticity is called the fuller's earth. The fuller's earth
contains the mineral montmorillonite which enhances its property of taking up water or other fluids.
Funnel Cloud A whirling mass of cloud that forms at the
heart of a tornado or water spout is cajled funnel cloud.
The funnel cloud is a downward ~!rojectiiig' funnel­
shaped cloud. I " . u' ,;',.