23 IV THE ENVIRONMENT The traditional territories of the Tahltan contribute to the nature, abundance, and people, as outlined above, are located distribution of resources available for within two natural physiographic regions, human exploitation. This section the Stikine Plateau and the Skeena summarizes the environmental factors which Mountains (as shown in Figure 4). The have influenced human occupation of the complex interaction of geologic processes, area. topography, climate, soils, and vegetation Physiographic Areas The Stikine Plateau is generally B.P, with even younger material overlying it characterized by flat and gently sloping (Souther 1970:63). Edziza derives its name upland surfaces which represent remnants of from the Tahltan term 'edziOa' meaning late Tertiary erosional surfaces, uplifted 'volcano ash and sand mountain,' and oral during the Pliocene. It also includes areas traditions describe eruptions which have modified by extensive Pleistocene volcanic forced people to move their camps quickly. activity and glaciation. The Stikine Plateau The base of the dome provides sources of is differentially dissected by several major good quality obsidian for stone tool river valleys, and is subdivided into several technologies. Most of the obsidian is black units each with its own distinct whose thinned edges sometimes show black geographical and geological characteristics lines and specks. Opaque green, grey, and (Holland 1976:49-55). blue varieties are less common while The Tahltan highland, running from mottled, striped or speckled varieties are northwest to southeast, is a transitional rare. These good quality obsidians were zone between the Boundary Range of the formed about 0.9 to 1.1 million years ago, Coastal Mountains and the plateau areas to according to fission track and potassium the east. The Mount Edziza Complex and argon dating, and have an abnormally high the Spectrum Range dominate the eastern uranium content (Souther 1970:63). edge of the highlands. Mt. Edziza is a The blocky alkali olivine basalt flows composite volcano rising to a height of from the younger cone volcanos do not 2700 metres (9000 feet) with an ice covered produce a workable glass suitable for peak. The first Edziza flow, dated to six making stone tools. However, the scattered million years ago by radiometric assay eruptions of these cones have caused sudden (Souther 1973:16), was followed by many changes in drainage patterns. Well defined similar flows forming a basal shield volcano lacustrine terraces on Mess Creek and with a radial system of canyons. During Klastline River mark the former extent of the late Pleistocene, until about 10,000 now dry lava dammed lakes that persisted years ago, activity in the central conduit for hundreds of years and may have built up the central dome and summit influenced the location of early campsites. crater with lava flowing down the radial The effect of lava dams on salmon valleys. migrations may also have had important Since 10,000 years ago, 30 to 40 repercussions on early human populations. eruptions from small pyroclastic cones have The absence of salmon in upper Iskut River produced mobile flows of blocky olivine may be attributed to an impassable barrier basalt. One of these on the north slope of recent lava from a cinder cone near the of Edziza has been dated to 1340 + 130 mouth of Forest Kerr Creek (Souther 1970:55). 24 TAHLTAN ETHNOARCHAEOLOGY The plateau areas, including Nahlin, such as marmots. Kawdy, Tanzilla, Spatsizi, and Klastline The Skeena Mountains extend south from Plateaus, have gently rolling upland the Spatsizi and Klastline plateau areas. surfaces of low relief, lying mainly above The transition between the plateau areas timberline at 15 00 metres (5 000 feet). and the mountains is represented by gently These areas support a wide range of sloping upland areas which are remnants of subalpine and alpine vegetation including dissected late Tertiary erosional surfaces. grassland communities, low lying shrubs, Drained by the Stikine, Nass, and Skeena mosses, and lichens. Within the Spatsizi Rivers, the Skeena Mountains consist of a Plateau, Pojar (1976) has identified more series of ranges divided by prominent than 370 species of vascular plants and northwesterly trending valleys. The valley over 200 species of mosses and lichens. bottoms lie at 2,500 to 4,000 feet (750 to These rich habitats support large 1200 m) in elevation and are wide and drift populations of larger game such as caribou, filled (Holland 1976:55). sheep, and goats as well as small animals Climate Most of the study area has a climate Table 2 Hours of Direct Sunlight which is in direct contrast to that of the Coastal Mountains. Situated within the Latitude December 21______Tune 21 rainshadow of the Coast Mountains, the Stikine Plateau has low precipitation, 56° 6 hr 57 min 17 hr 37 min averaging 12 to 23 inches (3 0-5 8 cm) 5 7° 6 hr 41 min 17 hr 56 min annually. Precipitation is particularly low 58° 6 hr 24 min 18 hr 15 min in the Tahltan highlands adjacent to the 59° 6 hr 08 min 18 hr 34 min mountains and increases eastward towards 60° 5 hr 52 min 18 hr 53 min the Cassiar Mountains. The area also experiences extremes in temperature, (Kendrew and Kerr 1956:156) although it is characterized by long cold winters and short cool summers, due to the combined factors of high northern latitude The major rivers freeze over by the end and high elevation of most of the area. of November and are closed to navigation by The amount of direct sunlight received boat until late April. At higher elevations, within the study area varies greatly from lakes start to freeze over in October and do summer to winter as shown in Table 2. not open again until late May or June. The long hours of daylight during summer Within the study area marked differences contribute to high plant productivity of in topography, climate, soils, and vegetation more hardy frost resistant species. Low are related to elevational zonation in local rainfall, combined with short frost free land forms. These differences are presented summers in the Stikine Plateau, prohibits according to the biogeoclimatic classification extensive horticulture or agricultural system developed by Dr. V.J. Krajina (196 5, activities except in a very restricted portion 1969). of the Middle Stikine Valley in the vicinity of Telegraph Creek. THE ENVIRONMENT 25 Biogeoclimatic Zones Alpine Tundra Zone between 900 and 1800 metres (3,000 to 6,000 feet). It is characterized by a cold The Alpine Tundra zone consists of continental climate (Dfc after Koppen) with treeless meadows, slopes, rocky ridges, short cool summers, and severe winters. snowfields, and icefields at high elevations Only tress which tolerate extended periods in mountainous as well as plateau areas. of frozen ground grow successfully in this Within the study area alpine tundra occurs zone. These include subalpine fir (Abies above 1500 to 1800 metres (5,000 to 6,000 lasiocarpa). white and black spruce (Picea feet) (Valentine et. aL 1978:154). The harsh glauca and mariana). Sitka alder (Alnus climate of the alpine environment is the sinuata). willows (Salix spp.), and shrub result of both increasing elevation and birch (Betula occidental is}*. latitude. The climate is described as Within the subalpine zone, Hutno-Ferric subarctic (Dfc after K op pen) with less than Podzols are the most common soils 25 frost free days. Frost may occur, throughout. On moderate to well drained however, any day of the year at higher sites on colluvial and morainal parent elevations. Absolute temperatures range materials white spruce and subalpine fir from 28° C to -45° C (83° to -49° F) while often grow in colonies or pure stands with the average temperature of the warmest a resulting thin acidic litter mat. On the month is less than 10° C (50° F). Average dry exposed plateau areas, such as the annual precipitation is 72 cm (29 in.) with Spatsizi, shrub willows and birch approximately 75% as snowfall (Krajina predominate, along with grassland 1965, 1969). communities. In some valleys subject to Factors such as high elevation, very cold cold air drainage from adjacent mountains, subarctic climate, lack of moisture, and shrub willows and birch, along with alpine rugged or often rocky terrain, all tend to species, occupy the valley floor as well as restrict soil formation processes in the upper elevations (Valentine e t.il. 1979: Alpine Tundra zone. Periglacial activity 154:55). Turbic Cryosol soils occur at such as cryoturbation is very active in this higher elevations where solifluction and zone resulting in churning of soil materials, nivation become active in moist areas patterned ground features, and poor horizon between clumps of krummholz, or dwarf, differentiation. Regosol landscapes are most tree forms. Although the Stikine Plateau common under these conditions (Valentine et_ lies south of the limit of discontinuous aL 1978:155). permafrost, permafrost occurs sporadically Alpine meadows occur under moist at higher elevations in the subalpine and conditions on flat or gently sloping alpine tundra zones, particularly in the topography where snow cover lasts longer. mountainous areas of the region. They have a short but colourful vegetative season and produce such species as grasses, Boreal White and Black Spruce Zone sedges, lupines, anemones, Indian paintbrush, and arnicas. A wide variety of mosses, This boreal forest zone occurs at lower lichens, and mountain heathers grow in the elevations in the major river valleys of the alpine tundra zone. Subalpine fir and Stikine Plateau from 150 to 900 metres scrub birch may occur in Krummholz, or (5 0 0 to 3 0 0 0 feet). This zone is dwarf, form in especially protected habitats characterized by a humid continental climate with moderate snow cover (Valentine et.