Geology Reference
In-Depth Information
sand
A loose, unconsolidated sediment made of par-
ticles of any composition with diameters in the sand-
sized range (0.625 to 2 mm in diameter). Most
sands have a preponderance of quartz grains, but cal-
cite grains derived from shells preponderate in some
sands.
siltstone
A consolidated sedimentary rock composed
chiefly of silt-sized particles that usually occur as
thin layers and seldom qualify as formations. Consoli-
dated silt.
slate
A fine-grained, clayey metamorphic rock. It read-
ily splits into thin slabs used in roofing.
sandstone
A medium-grained, bedded, clastic sedi-
mentary rock made of abundant rounded or angular,
sand-sized fragments in a fine-grained (silt or clay)
matrix. Consolidated sand. Arkoses are sandstones rich
in feldspar. Greywackes are sandstones containing rock
fragments and clay minerals. Flags or flagstones are sand-
stones with flakes of mica occurring along the bedding
planes.
slope
An inclined surface of any part of the Earth's
surface.
smectite
A name for the montmorillonite group of clay
minerals.
soil pipes
Subsurface channels up to several metres in
diameter, created by the dispersal of clay particles in fine-
grained, highly permeable soil.
schist
A strongly foliated, crystalline rock formed by
dynamic metamorphism. Readily split into thin flakes or
slabs.
soil wetness
The moisture content of soil.
suffossion
The digging or undermining of soil or rock
by throughflow.
sediment yield
The total mass of sedimentary parti-
cles reaching the outlet of a drainage basin. Usually
expressed as tonnes/year, or as a specific sediment yield
in tonnes/km
2
/year.
subaerial
Occurring at the land surface.
talus
Rock fragments of any shape and size derived
from, or lying at, the base of a cliff or steep rocky
slope.
serpentine
Any of a group of hydrous magnesium-
rich silicate minerals.
talus slope
A slope made of talus.
shale
A group of fine-grained, laminated sedimen-
tary rocks made of silt- and clay-sized particles. Some
70 per cent of all sedimentary rocks are shales.
tectosphere
A name for the continental lithosphere.
terracette
A small terrace; several often occur together
to form a series of steps on a hillside.
siderite
Iron carbonate, FeCO
3
, usually with a little
manganese, magnesium, and calcium present; a mineral.
toposphere
The totality of the Earth's surface features,
natural and human-made.
silica
Chemically, silicon dioxide, SiO
2
, but there are
many different forms, each with their own names. For
example, quartz is a crystalline mineral form. Chalcedony
is a cryptocrystalline form, of which flint is a variety.
vadose water
Subsurface
water
lying
between
the
ground surface and the water table.
Van der Waals bonds
The weak attraction that all
molecules bear for one another that results from the elec-
trostatic attraction of the nuclei of one molecule for the
electrons of another.
siliceous ooze
A deep-sea pelagic sediment containing
at least 30 per cent siliceous skeletal remains.
silicic
Pertaining to, resembling, or derived from silica
or silicon.
vermiculite
A clay mineral of the hydrous mica group.
silt
A loose, unconsolidated sediment of any com-
position with diameters in the silt-sized range (0.004
to 0.0625 mm in diameter). The chief component of
loess.
viscosity
The resistance of a fluid (liquid or gas) to
a change of shape. It indicates an opposition to flow.
Its reciprocal is fluidity.
