Landforms of British Columbia 1976 - Department of Geography

Between the Taku &nd Sheslay Rivers the highland consists of gently sloping
upland surfaces lying between 5,000 and 6,000 feet, with a few peaks rising higher.
They are remnants of an erosion surface which has been dissected into blocks,
some of which are of considerable size.
Between the Sheslay and Iskut Rivers the degree of dissection is somewhat
greater, and the amount of undissected upland much less. Sharp peaks rise to
elevations of 7,267 and 7,690 feet northeast of Yehiniko Lake and to 8,386 feet
at Hankin Peak between Mess Creek and Iskut River. The shield volcano at Mount
Edziza rises to an elevation of 9,143 feet, well above the general level of upland
surface, and dominates the surrounding terrain.
The relief within the Tahltan Highland is controlled by the depth of incision
reached by the Taku and Stikine Rivers and their tributaries, which flow at
elevations ranging from less than 500 feet in the main valleys to about 2,500 feet
at Trapper Lake, Mess Lake, and Mowdade Lake.
The eastern edge of the highland is dominated by the great shield volcano
culminating in glacier-clad Edziza Peak (see Plate XLVIIA) . Pleistocene and
older eruptions of lava and ash built the dome-like mountain above the general
plateau level and poured lava over an area 50 miles long and 10 miles wide on the
east side of Mess Creek. The 9,143-foot peak is a composite volcano, but much
of its mass appears to be made of older rocks, over which the flows form probably
a relatively thin veneer.
“ Lava flows and volcanic ejectamenta of post-Glacial to modern age form
conspicuous bodies along the east side of and within the Coast Mountains from
Telegraph Creek to Unuk River. Several flows, poured from outlets on the flanks
of Edziza Peak, blanket the north, east, and south slopes of that mountain, and
some have advanced into the present forest near Buckley Lake and Nuttlude Lake.
Small flows and remnants of flows are confined to the inner canyon of the Stikine
River, overlying glacial and river deposits. Cinder cones and breccia pipes, very
friable but quite unmarred by erosion, are conspicuous features of the Edziza-
Spectrum Range area.“*
The Spectrum Range, which extends south of Edziza Peak, is included within
the Tahltan Highland. It is named for the brilliantly coloured altered lavas which
underlie it.
Glaciation during the Pleistocene was intense, and glaciers still occupy peaks
south of Mount Edziza. The upper limit of Cordilleran ice reached an elevation
of about 6,500 to 7,000 feet. Above that elevation, peaks have sharp matterhom
appearances due to the intense cirque erosion that ensued; below that elevation,
when the ice cover disappeared, cirque erosion was largely restricted to northern
and eastern aspects. The main valleys of the Taku, Sutlahine, Tahltan, Stikine,
and Iskut Rivers and Mess Creek served as discharge avenues for glacial ice and
were straightened and considerably modified by its passage.
[References: Kerr, F. A., “ Lower Stikine and Western Iskut River Areas,”
Geol. Surv., Canada, Mem. 246, 1948; “ Stikine River Area,” Geol. Surv., Canada,
Map 9-l 957.1
[Photographs: B.C. 538:75; B.C. 541:2, 7; B.C. 695:lOO; B.C. 698:33.]
Taku Plateau
The Taku Plateau (see Plate XVIA) lies east of the Tagish and Tahltan
Highlands and is flanked on the east by the Kawdy and Nahlin Plateaus.
* Gd Surv., Canada, Map 9-1951, 111ar&1a1 note.
50