Geoscience Reference
In-Depth Information
event or location within a broader
sedimentary environ-
ment
.
Sedimentology
The study of the character, origin and
dispersal of sediments and sedimentary rocks.
Segregated ice lens
A type of
ground
ice formed by the
migration of pore water to a freezing plane and displacing
unconsolidated soil particles to form a discrete ice lens.
Seif dune
A large, sinuous linear dune drawn out parallel
to the wind direction.
Seismic activity
The sudden release of accumulated
stress in rocks subjected to tectonic and other deformation
and the Earth shock waves or earthquakes which it
propagates.
Seismic sea wave
A travelling ocean surface wave caused
by
seismovolcanic
activity which grows in height as it
enters shallow coastal waters and frequently causes
damage and loss of life; often mistakenly confused with a
tidal wave
.
Seismovolcanic
The close association between volcanic
and earthquake activity whereby either may trigger the
other, and their mutual concentration at plate boundaries.
Sensible heat
Saturated overland flow
Surface water discharge in sheet
rather than channel form, generated where the soil water
table breaks the land surface.
Scattering
The process whereby radiation is dispersed
in all directions by particles. The particles can be from the
size of molecules upwards. Meteorologically, radiation
which has been scattered is known as diffuse radiation.
Scenario
A predicted sequence of events; often used in
relation to climate or emissions of atmospheric pollution.
A variety of climate scenarios can be illustrated in relation
to particular levels of greenhouse gas emission.
Schistosity
A rock texture in coarse-grained material
with close, sub-parallel planes formed by the arrangement
of
platy
minerals; a rather coarser form of cleavage.
Scree
Angular rock debris or
talus
which accumu-
lates on slopes below the rock wall from which it was
weathered; it may be partially gravity-sorted and
maintains a slope angle dependent on its friction strength.
Sea-floor spreading
The lateral spread of the sea floor
generated by
mantle convection
and consequential
formation of new ocean crust at a mid-ocean ridge; the
driving mechanism of
plate tectonics
.
Sea ice
Floating ice formed by the freezing of sea water;
not to be confused with floating
glacier
ice.
Sea level
The mean surface elevation of the sea,
normally excluding transient changes induced by tides,
atmospheric pressure,
upwelling
and water influx.
Seamount
A wholly submerged, submarine mountain;
many are former sea-floor volcanoes.
Secondary (S) wave
A slower-moving earthquake wave
which oscillates at right-angles to its direction of travel
and can only pass through rock (see also
primary wave
).
Secondary succession
Successions which start when
human activities cease (e.g. abandonment of farming) or
when ecosystems recover after a disturbances (e.g. fire,
avalanche).
Sediment balance
The volumetric input, storage and
output of sediment which constitute the sediment budget
of a
drainage basin
per unit of time, usually a calendar year.
Sedimentary
The description of a major group of both
unconsolidated and
lithified
rocks formed by the eventual
accumulation of rock and organic debris after a period of
transport, suspension or solution.
Sedimentary basin
A geographical area in which sedi-
ments accumulate, generally in the form of a continental
or marine depression which acts as a gravitational 'sump'.
Sedimentary environment
The heat we can feel and measure with a
thermometer.
Sensitive clay
A clay whose undisturbed strength is
four to eight times greater than its disturbed strength and
is therefore particularly prone to failure.
Sequestration
Literally meaning the process of
'isolating' or 'confiscating', and used in climate change
science of the processes, in the global carbon cycle,
whereby carbon is 'locked up' in soils, vegetation and
sedimentary carbonates.
Seral stage
A stage in a sere when the area is occupied
by a community which creates conditions more and more
favourable for a succeeding community.
Sere
An alternative term for
succession
.
Set-down
The local, minor fall in water level experi-
enced in the surf zone when
edge waves
and incoming
waves are out of phase.
Set-up
The local, minor rise in water level experienced
in the
surf zone
when
edge waves
and incoming waves
coincide.
Severn bore
The
bore
which marks the leading edge of
incoming tides at the head of the Bristol Channel, Britain's
largest marine inlet experiencing one of Earth's highest
tidal ranges.
Shape of soil structure
The morphology of
the
individual peds which make up the soil structure.
Shear strength
The sum of internal forces in a rock or
soil capable of resisting shear which determines the
maximum
shear stress
the material can endure without
failing.
A general location in which
groups of
genetically related
sedimentary facies
are
deposited, such as a fluvial or marine environment.
Sedimentary facies
A parcel of sediment with distinct
internal characteristics reflecting a particular depositional
