Download Unit 1 Major land forms and water forms DEFINITIONS

Unit 1 Major land forms and water forms
abrasion. The grinding away of bedrock by fragments of
rock incorporated in ice, water, or wind.
alpine glacier. A mass of ice, situated on an upland, which
may be moving, or has moved, overland. See also
continental glacier.
anticline. An arch-like upfold in buckled, bent, or
contorted rock. See also syncline.
arcuate delta. A fan-shaped delta, like that of the Nile.
arete. A steep knife-edged ridge between cirques in a
mountainous region.
ash. A fragment of solidified lava, less than 4 mm across,
ejected during explosive volcanic eruptions.
ash-and-cinder cone. A volcanic peak with a roughly
circular base tapering to a point, formed by layers of
ash and lava thrown out
bay. A wide-mouthed recess in the line of the coast, filled
with sea water and with open access to the sea.
bay bar. A ridge of mud, sand, or shingle extending
acrosss a bay. It may be formed when spits stretch out
from each side of the bay and meet.
bay beach. An accumulation of sediment deposited by
waves and longshore drift along a bay.
block mountain. A mass of upland, bounded by faults. The
surrounding rocks may have sunk, the mountain block
may have risen, or both may have occurred.
chemical weathering. The breakdown of rocks that causes
chemical change, including the processes of corrosion,
hydrolysis, and oxidation. See also physical
weathering.
cirque. A circular hollow cut into bedrock during
glaciation. The side and back walls are steep but the
front opens out downslope.
composite cone. A volcanic peak with a roughly circular
base tapering to a point, formed from lava flows and
layers of ash. In a composite cone, smaller cones form
through vents on the flanks of the volcano.
compressional force. A force pushing into a part of Earth's
crust, causing it to buckle. See also tensional force.
continental glacier. A mass of ice, situated over most of a
continent, which may be moving, or has moved,
overland.
corrosion. The erosion of rock by solution.
delta. A low-lying area found at the mouth a river and
formed of deposits such as silt laid down by rivers.
Deposition occurs as the river's speed, and hence its
silt-carrying capacity, is checked when it enters the
more tranquil waters of a lake or sea.
denudation. The laying bare of underlying rocks by the
processes of weathering and erosion. See also
gradation.
deposition. The dropping of material which has been
picked up and transported by wind, water, or ice.
desertification. The spread of desert-like conditions in
semi-arid environments.
digitate delta. A delta with long "fingers" of sediment
extending into the sea.
divide. A line of separation between waters flowing to
different rivers, basins, or seas.
drainage basin. The area of land drained by a river and its
tributaries.
drumlin. A long hummock or hill, egg-shaped in plan
and deposited and shaped under an ice sheet or very
broad glacier while the ice was still moving. The end
facing the ice is blunt while the other end is shallow
and its point is in the direction of the ice flow.
erratic. A large boulder of rock differing in character
(composition, structure, texture, and hardness) from
the pre-existing rock on which it rests. The boulder has
been moved on the surface of a glacier.
estuarine delta. A delta formed in that area of a river
mouth which is affected by sea tides.
faulting. The fracturing of the surface of Earth's crust
caused by the travelling of rocks relative to each other.
fiord. A long, narrow arm of the sea which is the result of
the "drowning" of a glaciated valley.
fold mountain. An upland area formed by the buckling of
Earth's crust. Many fold mountains are associated with
destructive or collision margins of plates.
folding. The buckling, bending, or contortion of rock.
glacier. A mass of ice which may be moving, or has
moved, overland.
gradation. The levelling of a land surface by erosion and
deposition.
hanging valley. A high-level tributary valley from which
the ground falls sharply to the level of the lower, main
valley. The depth of the lower valley may be attributed
to more severe glacia-tion because it contained more
ice.
headland. An area of high land jutting out into the sea.
hydraulic pressure. The pressure of water. Hydraulic
pressure is an erosional force acting in such ways as
directly removing loose bedrock.
hydrolysis. The chemical reaction of a compound with
water. Hydrolysis is an important component of
chemical weathering and of soil formation.
lateral erosion. Usually of rivers, erosion of the banks
rather than the bed. See also vertical erosion.
lateral moraine. A landform deposited by a glacier or ice
sheet at the side of the glacier.
lava. Magma which has flowed over Earth's surface.
leaching. The movement of water down the soil profile.
This results in the movement of soil constituents,
including humus, to the lower soil horizons.
leeward. Referring to the side sheltered from the wind.
See also windward.
longshore drift. The movement of sand and shingle along
the coast. Waves usually surge on to a beach at an
oblique angle and take sediment up and along the
beach. As the wave water returns downslope to the
sea, it usually drains back along the beach at an angle
more nearly perpendicular to the coast, taking
sediment with it.
magma.
The molten rock found below Earth's crust
which can give rise to igneous rocks. See also lava.
mature river. A river characterized by many welldeveloped tributaries, a broad, flat valley with a welldeveloped floodplain, and a relatively broad channel
with meanders. Water moves efficiently in mature
rivers since erosion and deposition are almost
balanced.
meander. A winding curve in the course of a river.
medial moraine. A landform produced where two lateral
moraines combine.
overthrust fault. A fault that has previously under
normal fault. A fault in which rocks have moved down the
slope of the fault.
ocean current. A permanent or semi-permanent horizontal
movement of unusually cold or warm surface water of
the oceans, to a depth of about 100 m. The global
system of winds is the most important cause of these
currents, which are also affected by variations in the
temperature, and hence density, of the water, and by the
coriolis force.
old river. A river characterized by extremely flat relief, little
or no slope, very little velocity and elaborate meanders.
Because of their low velocity and lack of slope, old
rivers tend to be muddy with swampy areas nearby.
outwash plain. A plain formed by sediments washed out
by glacial meltwater and deposited beyond the ice sheet
or glacier supplying the water and the debris. Such
deposits are usually sorted with the coarsest sediment
being deposited nearer to the ice front and finer
material being laid down further away.
overthrust fault. A fault that has previously undergone
folding, with one set of rock layers pushed up and
thrust over other rock layers.
oxidation. The absorption by a mineral of one or more
charged oxygen atoms (ions). Oxidation is a major
type of chemical weathering, particularly in rocks
containing iron.
peninsula site. A site on a piece of land jutting into, and
almost surrounded by, the sea.
physical weathering. The disintegration or splitting up in
situ of rock without chemical change. Processes
include exfoliation and frost fracture. See also
chemical weathering.
plain. A level tract of land.
plate. A rigid segment of Earth's crust which can "float"
across the heavier, semi-molten rock below. The plates
making up the continents are less dense but thicker than
those making up the oceans.
Thus, a plate is part of the lithosphere which moves
over the plastic asthenosphere.
plateau. An extensive, relatively flat upland area.
plate tectonics. The theory that Earth's crust consists of eight
large and several small plates. The movement of some
plates causes earthquakes and volcanoes. This occurs
when one plate plunges below another. At oceanic
ridges, plates divide and magma wells up from Earth's
interior.
range. A row of mountains.
reverse fault. A fault, perhaps caused by a com-pressional
force, where movement is up, rather than down, the
face over which movement occurs.
rift valley. A valley bounded by two roughly parallel
faults formed when the rocks of its base moved down
the fault plane.
sand dune. A hill or ridge of sand sorted and accumulated
by wind action. Once a dune is formed, sand will
settle on it rather than on bare surfaces. This is because
the friction of the sandy surface is enough to slow
down the wind, which then sheds some of its load. See
also barchan.
sea arch. The feature which results when two caves
occurring on either side of a headland are cut until they
meet. Arches are relatively temporary features of the
landscape, as roof fall isolates the seaward end which
then becomes a stack.
sea cave. A large, natural hollow in a headland caused by
wave erosion.
sea-floor spreading. The creation of new crust as magma
rises up at a plate margin. The magma creates new
oceanic crust as the far end of the plate moves away.
seismology. The study of earthquakes and of other Earth
movements such as those that may be caused by human
beings.
shield cone. A volcano formed of successive eruptions of
free-flowing, relatively thin lava which spreads over a
large area, creating a broad, gently sloping dome tens
of kilometres across and around 1 km high.
spit. A ridge of sand running away from the coast, usually
with a curved seaward end. Spits grow in the prevailing
direction of longshore drift. Their ends are curved by
the action of waves coming from different directions.
stack. An isolated islet or pillar of rock standing up from the
sea bed close to the shore. A stack is a residual feature
formed when marine erosion attacks a cliff.
syncline. A downfold of rock layers. See also anticline.
tensional force. A stretching force in Earth's surface which
may cause faulting. See also com-pressional force.
terminal moraine. A landform deposited by a glacier or ice
sheet which marks the end of a glacier.
topography. The natural and human features of Earth's
surface.
vent. An opening in the crust through which volcanic
material flows. Some volcanoes have a single, central
vent, while others have a line of vents or side vents.
vertical erosion. Usually of rivers, erosion of the river bed.
See also lateral erosion.
volcano. An opening of the crust out of which magma,
ash, and gases erupt. The shape of the volcano depends
very much on the type of lava. Most volcanoes are
located at plate margins.
wave refraction. The change in the approach angle of a
wave as it moves towards the shore. This change in
speed causes the straight line of a wave to "bend" so
that the line of the wave mirrors the submarine
contours. Refraction causes waves to converge on
headlands and diverge in bays. This means that the
energy of the waves is concentrated on the headlands
rather than on the beaches.
weathering. The breakdown, but not the removal, of
rocks. See also erosion.
youthful river. A river characterized by a steep slope, a
relatively small volume of water, rapid flow, and a
narrow, relatively straight V-shaped valley.