These terms are the bare minimum vocabulary you should be able to use and understand when sitting the examination. You are free to download this page for your own educational use.
- Aquifer
- A bed of rock which allows water to percolate
through it and accumulate within the spaces between the rock particles.
- Artesian Well
- A type of well from which water flows without
assistance. This is caused by the base of the well being in rock layers
which are saturated and contain water under pressure. The pressure,
called hydrostatic pressure is generated by the top of the well being
below the level of the water supply. This can occur when a well is sunk
in the base of a valley, and the porous rocks it exploits extend some
distance up the sides of the valley.
- Bedload
- The load of a stream or river which is moved
along its bed.
- Bourne
- A type of stream, common in the chalk areas of
Southern England, which flows only during the wetter parts of the year
when the water table rises above the bed of the stream. For the remained
of the year the watertable is below the stream bed, leaving the stream
dry.
- Catchment Area
- The catchment area, or drainage basin, of a river
is the land area which drains into the river. All rainfall in the
catchment area of a river will flow into the river. A valley will
usually form the catchment area for the river which flows in its base.
Rain falling in the next valley will flow into a different river.
- Clints
- A weathered block of limestone surrounded by
Grykes, the weathered joints of the rock. Clints and grykes
are typical of limestone pavements and karst landscapes.
- Consequent River
- A river which flows down the slope of the
landscape in the direction of the rock dip. Literally the river is a
'consequence' of the slope.
- Coombs
- A hollow in the side of a chalk valley, or
sometimes another word for a corrie.
- Cut Off
- A meander in a river course which is literally
cut off from the present river. When a meander has almost formed a
complete loop, the narrow neck of land may be eroded in flood
conditions, allowing the river to by-pass the bend. Silt begins to build
up at the entrances to the cut off section, eventually creating a lake
known as either a cut off or an ox-bow lake.
- Delta
- A triangular area of deposited silt or alluvium
at the mouth of a river. It will occur where a river carries a heavy
load and empties into a shallow sea. As the area of silt increases the
river tends to divide into many smaller channels. The mouth of the Nile
in Egypt forms a fan shaped delta known as an arcuate delta. The more
lobate delta at the mouth of the Mississippi is known as a bird's foot
delta.
- Dendritic Drainage
- A drainage pattern which resembles the trunk and
branches of a tree when viewed from above. Small streams (twigs) flow
into larger streams (small branches) which in turn flow into small
rivers (large branches). The small rivers eventually all flow into a
single main river (the trunk).
- Dry Valley
- A valley, usually on either limestone or chalk,
which should contain a stream but doesn't. This is caused by the water
table level being below the land surface. All rain permeated through the
porous rock to join subterranean water courses.
- Earth Pillars
- A very tall column of soil protected by a large
rock perched on top. The rock protects the soil beneath it from erosion
caused by rainfall. Earth pillars may be twenty or more feet high and
occur most frequently in mountainous areas.
- Flood Plain
- A flat area of land on either side of a river.
The soil consists of alluvium which is deposited every time the river
floods and overflows it's banks. The land tends to be slightly higher
along the edges of the river where a levee forms
- Gorge
- A valley with vertical walls created by the
headward migration of a waterfall. As the waterfall
retreats due to erosion, a gorge is formed downstream. Good examples
occur downstream of the Niagara Falls in Canada, and below High Force on
the River Tees, UK.
- Gradient
- The angle of slope down which a river or stream
flows. A steep gradient is typical of a young mountain stream, whilst a
gentle gradient is typical of a mature lowland river.
- Grykes
- The weathered joints in limestone which surround
clints. The grykes are weathered and enlarged by chemical
weathering of the limestone, eventually leaving an isolated block of
limestone, a clint, surrounded on all sides by grykes.
- Gully
- A small ,narrow and usually long channel on a
hillside created by flowing water.
- Infiltration
- The process by which rain water soaks into and
through the ground.
- Karst Landscape
- The classical landscape of Limestone areas,
featuring limestone pavements, caves, swallow holes, and other limestone
features. Almost all drainage is below the surface, leaving the ground
very dry and barren. The name Karst comes from the area of Yugoslavia
along the Adriatic coast.
- Knickpoint
- An abrupt change in slope or gradient of a river,
often characterised by waterfalls or rapids over hard rock areas. It is
caused by uplift of the land or a drop in sea level leading to rejuvenation.
- Landslide
- The mass movement of earth and rocks down a
slope. Landslides are often caused by soil becoming too heavy to remain
stable due to saturation by rainwater, or by earth tremors such as
volcanic eruptions and earthquakes.
- Lateral Erosion
- A river valley is widened by erosion of the
valley sides. This is lateral erosion. The deepening of the valley due
to river action is vertical erosion. In youthful rivers, vertical
erosion is the most active form, whilst in mature rivers, lateral
erosion is more pronounced than vertical.
- Levees
- Raised banks of alluvium along the edges of an
old river. When a river floods its banks, the water spreads out and
rapidly loses its load carrying ability. Deposition occurs close to the
banks, increases their height. When not flooding, sediment is deposited
on the river bed. After a period of time the river and its levees stand
above the general level of the surrounding flood plain.
- Meander
- A bend or curve in the course of a river. The
river constantly alters the shape of a meander by eroding the outside of
the bend and depositing sediment on the slipoff slope, the
inside of the bend.
- Mouth
- The part of a river where it enters the sea, a
lake or even another larger river.
- Oasis
- An area within an arid desert area where water is
present at or near the surface. Clusters of Date Palms are typical
indicators of an oasis within the Sahara Desert.
- Ox-Bow Lake
- A meander in a river course which is literally
cut off from the present river. When a meander has almost formed a
complete loop, the narrow neck of land may be eroded in flood
conditions, allowing the river to by-pass the bend. Silt begins to build
up at the entrances to the cut off section, eventually creating a lake
known as either a cut off or an ox-bow lake.
- Peneplain
- A large area of almost flat land. The area is
eroded flat by the action of rain and river erosion. More resistant
rocks may as isolated sections above the general level of the land. A
highland peneplain is known as a plateau.
- Percolation
- The movement of water down through the soil or
cracks in rocks.
- Pervious
- Something which allows water to pass through it
due to cracks or defects is pervious. A pervious rock differs from a
porous one in that a porous rock allows water to flow throuFebruary 24, 2006ement through the pores. For
example, solid granite is neither porous nor permeable. Granite
containing cracks and faults may allow water to pass. It then becomes
permeable, but is still not porous.
- Plunge Pool
- A deep pool which forms at the base of a
waterfall. Water and its load gain velocity by falling at a waterfall
thus increasing erosion directly below the fall. Once a depression
forms, currents cause pebbles to swirl around within it, increasing the
erosion and thus the depth of the plunge pool.
- Porous
- A porous substance allows water to pass through
it, making use of the spaces between the pores. Rocks such as sandstone
are porous since they allow water to penetrate the gaps between the rock
particles.
- Pot Hole
- A vertical hole into which a surface stream
flows, or used to flow. Pot holes occur in limestone areas where
subterranean drainage is developed. The Pot Hole is the route taken by
the water from the surface to the underground drainage. It may also be
known as a sink hole or a swallow hole.
- Radial Drainage
- When rain falls on the top of a dome shape it may
run off the surface in any direction. Domed areas such as Dartmoor in
the South West of the UK exhibit radial drainage. When viewed from above
the pattern of rivers resembles the spokes of a wheel, the hub being the
top of the dome.
- Rapids
- When a river crosses a band of hard rock
differential erosion occurs. The hard rocks erode less quickly than the
softer rocks below them. This steepens the river gradient and increases
the velocity of the water. A waterfall or rapids will be formed where
the water rushes over the hard rocks producing white water as it speeds
down the steepened section.
- Rejuvenation
- When land is uplifted, or the base level of a
river is lowered for any reason, the river's erosive power is increased.
The gradient down which it flows is increased and it's powers of vertical
erosion are also increased. The river becomes more active and is
literally rejuvenated.
- Riffle
- An area of a river which is wide and shallow, the
water flowing over a pebble bed with protruding rocks. Friction is high
due to the shallow depth and rough bed. Riffles occur between pools,
which are located within meanders. Water flow is divergent
at a riffle, and convergent in pools.
- River Basin
- The area of land drained by a main river and its
tributaries. See catchment area
- River Cliff
- The outer bank of a meander
experiences considerable erosion and is often concave and relatively
high when compared with the inner bank. It forms a cliff like structure,
hence the name river cliff.
- Run Off
- Rainfall which flows across the surface rather
than sinking into the ground.
- Sink Hole
- A vertical hole into which a surface stream
flows, or used to flow. Pot holes occur in limestone areas where
subterranean drainage is developed. The Pot Hole is the route taken by
the water from the surface to the underground drainage. It may also be
known as a pot hole or a swallow hole.
- Slip Off Slope
- The inside edge of a meander. The
inside edge of a meander is characterised by slow flow, deposition and
the creation of a gently sloping profile which creates progressively
deeper water as distance from the inner bend increases.
- Solution
- The part of a river's load which is dissolved in
the water. An example is Calcium Carbonate which is dissolved from
limestone by acidic water. See Stalactite and Stalagmite
for more information about Calcium Carbonate in solution.
- Source
- The point at which a river starts.
- Spring
- A natural source of water rising out of the
ground. A spring will occur where the watertable is at the surface.
Where rain water percolates through permeable rocks then meets an
impermeable layer the water will flow along the boundary. If that
boundary happens to occur on a hillside, the water will appear as a
series of springs along the side of the hill. This line is the spring
line.
- Stalactite
- A formation of Calcium Carbonate which hangs down
from the roof of a cave or similar structure within limestone rocks.
Water rich in dissolved Calcium Carbonate ( see solution )
seeps through the roof and, as it drips, some of the Calcium Carbonate
is left deposited on the roof. Over a considerable period of time the
Calcium Carbonate accumulates to form an icicle shaped formation which
grown downwards. See Stalagmite
- Stalagmite
- Similar to a stalactite in formation, a
Stalagmite is formed when drips of Calcium Carbonate rich water fall
onto the floor of a cave. As the drip hits the floor some of the
dissolved Calcium Carbonate is deposited. Over a period of time the
deposit accumulated forming a column of Calcium Carbonate growing up
from the floor. Due to the splashing of the drips, Stalagmites are
generally wider and more robust than stalactites.
- Subsequent River
- A river which does not flow down the main slope
of the land. See Consequent River and Trellis
Drainage .
- Suspension
- The part of a river's load which is carried as
particles held in the water. It is load in suspension which gives water
a cloudy appearance. See bedload and solution
- Swallow Hole
- A vertical hole into which a surface stream
flows, or used to flow. Pot holes occur in limestone areas where
subterranean drainage is developed. The Pot Hole is the route taken by
the water from the surface to the underground drainage. It may also be
known as a pot hole or a sink hole.
- Trellis Drainage
- This form of drainage develops on a surface
composed of alternate layers of hard and soft rocks which all dip in the
same direction. A main river will develop which flows in the direction
of the slope. This is a Consequent River . It is fed by
rivers which form in the vales on either side. These rivers will follow
the softer bands of rock which are generally at right angles to the main
river. The overall pattern resembles a trellis, hence the name.
- Tributary
- A river or stream which feeds a larger water
course.
- Vertical Erosion
- Vertical erosion is caused by the erosive action
of rivers cutting downwards. This deepens river valleys. The valley is
widened by lateral erosion
- Water Table
- The level of the groundwater, or the level below
which the rocks are saturated with water. During dry weather the water
table will sink, and during wet weather it will rise nearer to the
surface. The lowest point to which the watertable sinks is known as the
permanent watertable. See Zone of intermittent saturation,Zone of
non-saturation and Zone of permanent saturation .
- Waterfall
- When a river crosses a band of hard rock
differential erosion occurs. The hard rocks erode less quickly than the
softer rocks below them. This steepens the river gradient and increases
the velocity of the water. A waterfall or rapids will be
formed where the water rushes over the hard rocks producing white water
as it speeds down the steepened section. The waterfall may occur at the
sight of a Knickpoint
- Zone of intermittent
saturation
- The area between the normal level of the
watertable and the level it reaches after heavy rainfall. This
area is only saturated during periods of wet weather.
- Zone of non-saturation
- The area of the ground between the surface and
the top of the watertable. Water always passes through
this zone which never becomes saturated.
- Zone of permanent
saturation
- The part of the ground in which the pores are
always saturated with ground water.
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