SUBCLASSES AND SUBTYPES

Subclasses for Mass Movement Processes
Subclasses for Fluvial Processes
Subclasses for Permafrost Processes
Bedrock Subclasses
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Subclasses and subtypes can be incorporated in terrain unit symbols to provide further information about a surficial material or a geomorphological process.

Note: Subclasses have been redefined (1997).
Note: Subtypes were previously included in subclasses.

SUBCLASSES FOR GEOMORPHOLOGICAL PROCESSES

For some purposes, it is useful to be able to map the specific types of geomorphological processes that are grouped together in the general classification presented in Geomorphological Processes. For example, in the general classification, rockfall, debris flows, etc., are grouped together as "rapid mass movement" (symbol: R). The use of subclass symbols enables these specific processes to be shown on the map. Subclasses are defined as subdivisions of the general categories of the Geomorphological Processes classification; symbols and definitions of process subclasses are specified within the Terrain Classification System (see: Subclasses for Mass Movement, Subclasses for snow Avalanches, Subclasses for Fluvial Processes, and Subclasses for Permafrost Processes in this chapter. In some cases, features that result from a particular process and thus indicate that the process is (or has been) active, are used to define the process. For example, "type of back channel" (in subclasses for fluvial processes) implies certain physical and biological conditions and processes.

Application and Examples

Subclasses are represented by a lower case letter that is placed after the related general geomorphological process symbol. Up to three subclasses can be attached to each general geomorphological process. It is recommended that subclasses be used for relatively detailed, large scale mapping, especially where the objective of the mapping is slope stability assessment or identification of slope hazards.

Examples: a meandering river with backchannels containing
flowing or standing water year-round F^Ap-Mp

gullied bedrock cliffs where rockfall (b)
and debris flows (d) start (") Rs/Cv-VR"bd

talus slope receiving rockfall xrCk-Rb
bedrock and colluvium slope with major
avalanche tracks Rsk/Cv-Af

Subclasses for Mass Movement Processes

The following subclasses can be used, where appropriate, with the symbols -F (slow mass movement), -R (rapid mass movement) and -A (snow avalanches).

Table 1. Subclasses for Mass Movement Processes.

Subclass Name	Map Symbol	Definitions*
Initiation Zone	"	terrain unit includes sites or zones of instability, such as the headscarps of debris slides or earthflows and source areas for rockfall and debris flows; use with -F and -R to distinguish initiation zones from runout zones.
Slow Mass Movement: use the following symbols with -F
soil creep	c	slow movement of soil
rock creep	g	slow movement of angular debris under periglacial conditions (e.g. rock glaciers)
tension cracks	k	open fissures, commonly near crest of slope
lateral spread - in bedrock - in surficial material	p j	lateral extension of a fractured mass of bedrock or surficial material; movement is predominantly horizontal
Rapid Mass Movement: use the following symbols with -R
debris fall	f	descent of a mass of surficial material by falling, bouncing and rolling
rockfall	b	descent of masses of bedrock by falling, bouncing and rolling
debris flow	d	rapid flow of saturated debris torrent
debris torrent	t	rapid flow of a mixture of water, earth and vegetation debris down a steep, well-defined stream channel
Slow or Rapid Mass Movement: use the following symbols with -F or -R
earthflow	e	slow viscous flow of material containing a high proportion of silt and clay
slump -in bedrock - in surficial material	m u	sliding of internally cohesive masses of bedrock or surficial material along a slip plane that is concave upward or planar
slump-earthflow	x	combined slump (upper part) and earthflow (lower part)
debris slide	s	sliding of disintegrating mass of surficial material
rockslide	r	descent of large masses of disintegrating bedrock by sliding
Snow Avalanches: use the following symbols with -A
major avalanche tracks; active	f	in zones of coniferous forest: broad avalanche track(s) occupied by predominantly shrubby, deciduous vegetation; conifers are largely absent
minor avalanche tracks; active	m	similar to above, but relatively narrow; generally narrower than the height of adjacent trees
mixed major and minor avalanche tracks; active	w	polygon includes both major and minor avalanche tracks
old avalanche tracks	o	track are clearly visible on air photos but are less well defined than active avalanche tracks because they are partly or completely occupied by young conifers
* After Fairbridge, 1968; Swanston, 1974; Swanston and Swanson, 1976; Varnes, 1978; White, 1981.

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Subclasses for Fluvial Processes

The following subclasses can be used, where appropriate, with the process symbols -B (Braided Channel), -I (Irregularly Sinuous Channel), -J (Anastamosing Channel) and -M (Meandering Channel).They are intended for use primarily with bioterrain mapping, and with detailed mapping of riparian zones and fish habitat.

Table 2: Subclasses for Fluvial Processes

Subclass Name	Map Symbol	Definitions
progressive bank erosion	u	persistent bank erosion indicated by the presence of undercut banks, overhanging and fallen trees, and much timber in the channel; old air photos and historical information can also be used as evidence. Example: sF^Ap-Mu
abrupt channel diversion; avulsion	a	the present channel has recently shifted abruptly to a previously vegetated area; the former channel can be identified by air photos or on the ground. Example: gF^Ap-Ja Example: gF^Af-Ba
backchannels	b	small channels which may or may not be connected to the main channel. Example: sgF^Ap-Ib
permanent river-fed backchannels	p	backchannels joined to the main channel at the upstream end,allowing flowing or standing water all year. Example: sgF^Ap-Jp
ephemeral river-fed backchannels	e	backchannels joined to the main channel at the upstream end, but dry during the late summer. Example: sgF^Ap-Je Example: sgF^Ap-Jpe Example: gF^Af-Be
spring-fed backchannels	s	backchannels in which water is maintained during the late summer by the emergence of floodplain groundwater. Example: sF^Ap-Ms Example: sF^Ap-Msu
permanent tributary-fed backchannels	t	either flowing or standing water from tributaries is present in the backchannel all year. Example: sgF^Ap-Jt
ephemeral tributary-fed backchannels	d	backchannels normally fed by tributaries, but dry during late summer. Example: sgF^Ap-Jtr

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Subclasses for Permafrost Processes

The following subclasses can be used, where appropriate, with the process symbols -X (permafrost processes), -Z (periglacial processes).

Table 3: Subclasses for Permafrost Processes

Subclass Name	Map Symbol	Definitions
palsas, peat plateaus	p	flat-topped or rounded mounds and ridges of peat or peaty earth formed by differential frost-heaving; contain perennial ice lenses and a core of permafrost Example: Op-Xp
thermokarst: subsidence	t	ground-surface depressions which are created by the thawing of ice-rich permafrost and associated soil subsidence Example: zLpd-Xt
thermokarst: thermal erosion by water	e	gullies and depressions created by melting of ice-rich permafrost due to heat transfer from water bodies; either streams or lakes Example: mWj-XeV
thaw flow slides	f	slope failures caused by the thawing of permafrost Example: dzsMb-Xf
ice wedge polygons	w	intersecting narrow cracks that contain ice-wedges comprise polygonal patterns on the ground underlain by permafrost Example: sFt-Xw
patterned ground	r	a collective term for the regular surface features, such as stone polygons, frost boils and stone stripes, that are characteristic of ground that is subject to intensive frost (freeze-thaw) action Example: rCv-Xr Example: rCv-Zr

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Bedrock Subclasses

Note: Bedrock Subclasses are new (1997).

Bedrock types may be indicated on terrain maps where lithological information is of direct relevance to project objectives. For example, on a terrain stability map, a particular rock type that is correlated with unstable slopes can be shown. In ecosystem terrain mapping, rock types that exert a significant influence on soil and vegetation characteristics, such as limestone or serpentine, can be mapped. In general bedrock types will be mapped only occasionally, and on any given map, rock type will be shown for only a few polygons.

Bedrock symbols are listed below. Either the generalized (e.g., Clastic, calcareous, coarse grained: kf) or the specific (e.g.,Calcareous conglomerate: kn) terms can be used. Symbols are placed in front of the bedrock (R) symbol.

Example: limestone escarpment IsRs

serpentine scarp with
earthflows spRks/zCb-F"e

Table 4: Subclasses for Sedimentary Rocks

	EITHER		OR
Clastic	fine grained	kf	calcareous siltstone	kz
calcareous			calcareous mudstone	kd
			calcareous shale	kh
	medium grained	km	calcareous sandstone	ks
			calcareous greywacke	kg
			calcareous arkose	ka
	course grained	kc	calcareous conglomerate	kn
			calcareous breccia	kb
Clastic	fine grained	uf	siltstone	zl
non-calcareous			mudstone	md
			shale	sh
	medium grained	um	sandstone	ss
			greywacke	gk
			arkose	ak
	course grained	uc	conglomerate	cg
			breccia	bk
Precipitates	calcareous	pk	travertine	tv
			limestone	li
			dolomite	do
	non-calcareous	pu	gypsum	gy
			limonite	li
			barite	ba
Organic	calcareous	ok	marl	lg
	carbonaceous	oc	coal	co

Table 5: Subclasses for Igneous Rocks

	EITHER		OR
Intrusive	acid (felsic)	ia	syenite	sy
			granite	gr
			quartz monzonite	qm
	granodiorite	gd
	intermediate	ii	quartz diorite	qd
	basic	id	quartz gabbro	qg
			pyroxenite	py
			peridotite	pd
			dunite	du
Extrusive	acid (felsic)	ea	trachyte	tr
			rhyolite	rh
			dacite	da
	intermediate	ei	andesite	an
	basic	eb	quartz basalt	qb
			basalt	bs
	recent lava flow	la
	pyroclastic	ep	tuff	tu
			volcanic breccia	vb
			agglomerate	ag

Table 6: Subclasses for Metamorphic Rocks

>ar

	EITHER		OR
foliated	fine grained	ff	slate	sl
			phyllite	ph
	medium to course grained	fm	schist	sc
	gneiss	gn
			granite gneiss	gg
			diorite gneiss	dg
	course grained	fc	migmatite	mi
Non-foliated	fine grained	nf	argillite
			serpentinite	sp
	medium to course grained	nm	granulite	gl
			quartzite	qt
			hornfels	hf
	course grained	nc	amphibolite	am
			hornblendite	hb
	calcareous	nk	marble	mb
			dolomite marble	dm
			serpentine marble	sm

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SUBTYPES FOR SURFICIAL MATERIALS AND GEOMORPHOLOGICAL PROCESSES

For some purposes, it is useful to be able to map specific subcategories of surficial materials and geomorphological processes that are, at present, undefined in the Terrain Classification System. For example, within the context of project objectives, it may be useful to distinguish subcategories of till according to their mineralogy, or subcategories of gullies according to their morphology. Subtypes are defined as subdivisions of the classes defined for the Surficial Materials and Geomorphological Processes that are NOT specified within the Terrain Classification System.

Application and Examples

Subtypes should be defined only where their use is of direct relevance to project objectives. Symbols and definitions are the responsibility of the mapper. Symbols must be clearly defined in the map legend, and subtypes should be clearly defined in the project report.

Subtypes should not be defined where equivalent information can be indicated by pre-defined symbols, for example, to show differences in surficial material texture, or to define processes that can be described by the use of subclasses or qualifiers.

Subtypes are represented by a number that is placed immediately after the symbols defined in the Geomorphological Processesor Surficial Materials. Only one Subtype can be attached to a surficial material or process symbol.

Examples: blanket of calcareous till M1b

blanket of non-calcareous till M2b

mineralogy of till unspecified Mb

till blanket with steep-sided,
deeply incised gullies MB-V1

till blanket with shallow, rounded gullies Mb-V2

till blanket with gilly morphology
unspecified Mb-V

When subtypes are used, a short (<1 page) statement including: name of project; name and contract numbers for senior mapper; symbol(s) used, definition(s), and justification should be forwarded to the curator of the provincial database.

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SUBCLASSES AND SUBTYPES

SUBCLASSES FOR GEOMORPHOLOGICAL PROCESSES

Subclasses for Mass Movement Processes

Subclasses for Fluvial Processes

Subclasses for Permafrost Processes

Bedrock Subclasses

SUBTYPES FOR SURFICIAL MATERIALS AND GEOMORPHOLOGICAL PROCESSES

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Examples:	a meandering river with backchannels containing flowing or standing water year-round	F^Ap-Mp
	gullied bedrock cliffs where rockfall (b) and debris flows (d) start (")	Rs/Cv-VR"bd
	talus slope receiving rockfall	xrCk-Rb
	bedrock and colluvium slope with major avalanche tracks	Rsk/Cv-Af

Example:	limestone escarpment	IsRs
	serpentine scarp with earthflows	spRks/zCb-F"e

Examples:	blanket of calcareous till	M1b
	blanket of non-calcareous till	M2b
	mineralogy of till unspecified	Mb
	till blanket with steep-sided, deeply incised gullies	MB-V1
	till blanket with shallow, rounded gullies	Mb-V2
	till blanket with gilly morphology unspecified	Mb-V