415Rock fall the free falling of a newly detached segment of
bedrock of any size from a cliff or other very steep slopes.
Runoff Water which is not absorbed by the soil and flows to
lower ground, eventually draining into a stream, river, or
other bodies of water.
r-strategist species (r-strategists) Cf K-strategist species
S2 amount of hydrocarbon that escapes from the sample
during the thermal cracking in Rock-Eval analyzer,
expressed in mg HC/g sediment.
SSU rDNA Small SubUnit of Ribosomal DNA.
Saprophytism Ability of certain organisms to use dead or
decaying organic matter as source of energy.
Sauroctonous dragon killer, mostly used in early Christian
times (e.g. St Georges).
Scoria cone a volcanic cone formed by lava and or pyro-
clastics build up around a volcanic vent.
Seasonal overturn During winter, the lake water column
becomes unstable when the uppest layers are low dense
than the deepest ones. Therefore, the lake is affected by
a convective movement of the layers of the water column
that is called seasonal overturn.
Sedimentary event individual sedimentary bed recording
rare geological events at any scale.
Sedimentary facies lithological signature of sediments
including the color and the occurrence of sedimentary
structures, bedding and grain size distribution.
Sedimentary unit sedimentary layer composed by similar
sedimentary facies or any of the many characters, proper-
ties or attributes that sediments may possess.
Seismic reflection profile a cross section through the
subsurface produced by the propagation and reflection
of an acoustic wave into a sedimentary basin. It repre-
sents the layering geometry in the subsurface tens of
meters to kilometers below the surface, depending of the
frequency.
Sensory grid of degassing a collection of sensory percep-
tion of lake misbehavior (sight, hearing, taste, smell,
touch) assembled from scientist’s records of degassing
lakes in Cameroun and Italy (Table 1.2). It includes
observations at the lake or its surroundings, their far away
effects on the environment and damages to populations
and living beings. Used to re- interprete historical or leg-
endary accounts.
Sestonic particulate matter suspended in the water column.
Siderite iron carbonate mineral (Fe(II)CO 3 ) in the trigonal
crystal system.
Slide scar a scratch left on a sea floor/lake floor by subaque-
ous sliding or slumping.
Slump the sliding-down of a mass of sediment shortly after
its deposition on an underwater slope characterized by a
shearing and rotary movement along a curved basal slip
surface.
Social responses to degassing The social responses gener-
ated by lake disorders are very diverse. They depend on
the perioid and culture. They range from purely technical
(tunnels and canals) to lake cults with specific deities and
Christian communities on lake shores or in their vicinity,
lake-related legends and fantastic stories featuring fantas-
tic animals, as dragons, and/or marvelous events, includ-
ing the damages caused to populations (e.g. a “plague”)
and their iconographic representations.
Solifluction flowage of oversaturated soil and colluvium on
steep slope. Slow flowage produces smooth, gentle, con-
cave and convex landforms on slopes.
Sporogenesis Production of spores
Sub-bottom profile a very high resolution reflection profile
detailing the first few meters of the subsurface (m to tens
of meters).
Sunken city legends common legend found for many
lakes featuring a misbehaving city sunk into the lake;
interpreted as a transcription of the biblical Sodom and
Gomorrha myth. It appears in Pavin in the late XIXth and
is thought by guidebooks authors to be its original legend
since then
Surge or pyroclastic surge One of the pyroclastic density
currents (PDCs), a diluted current interpreted as moving
with a turbulent regime. Surges usually form fine grained,
stratified and cross-bedded deposits.
Syntrophic association A biological relationship in which
microorganisms of different species or strains are mutually
dependent on one another for nutritional requirements.
T-RFLP Terminal Fragment Length Polymorphism is a
culture- independent, rapid, sensitive and reproducible
method of assessing diversity of complex communities
without the need for any genomic sequence information.
The technique provides information on a collection of
microorganisms that may be present in a given sample.
Tephra The word ‘tephra’ is derived from the Greek tephra
(φ) meaning ash, and is a collective term for all the
unconsolidated, primary pyroclastic products of a vol-
canic eruption. It is inclusive of all grain sizes, includ-
ing fine ash (dust) (<0.06 mm), coarse ash (0.06–2 mm),
lapillus/i (2–64 mm), and block/s or bomb/s (>64 mm).
Strictly, ‘tephra’ is singular (it does not occur in Greek
in the plural form) and hence it is used as a collective
with singular verb forms. Note that in compound words
in English based on Greek roots, the original final vowel
(‘a’) is always replaced with ‘o’ to form derivatives such
as tephrostratigraphy.
Tephrochronology (Sensu Stricto) ‘Tephrochronology’
(sensu stricto) was defined as a dating method based on the
identification, correlation and dating of tephra layers that
is, essentially using tephra deposits as time- stratigraphic
marker beds to establish numerical or relative ages.Glossary