Physical Features

or ice-cap. Commonly a peak may have two or three small cirque glaciers
giving it a horn-like appearance. The largest ice-field entirely within the area
is about 9 miles long by 3 miles wide. It lies south of Seel Lake and supplies
several small ice tongues and one prominent valley glacier. West of the
headwaters of Morice Lake is another large ice-field, only part of which lies
within the map-area. The cirques on higher peaks of the Transitional Ranges,
such as Chikamin Mountain and Troitsa Peak, contain small glaciers, but
towards the eastern and lower ends of these ranges, at an elevation of about
5,000 feet, some cirques on the north side of the range are ice free. Evidently
alpine glaciation was formerly more extensive. This is borne out by many
instances of terminal and lateral moraines well in advance of their present
ice lobes, and such structures as hanging valleys, truncated spurs, and
U-shaped valleys.

Drift is abundant in the valleys and covers the plateau areas. The bulk
of the material is fluvioglacial in origin, particularly along the present
drainage channels, and consists mainly of silt, sand, and gravel. In one part
of Tahtsa River, about 8 miles below Kasalka Creek, the banks of the
former stream were red and blue varved clay.

Alluvial fans are common, particularly in the mountains where streams
from alpine glaciers enter lakes at the bottom of steep-sided mountains.
In several instances such fans were observed to have dammed the lake
completely or left only a narrow channel (see Plate III). Much of this
material is ultimately carried downstream by rivers such as the Tahtsa and
Whitesail and accumulates as deltaic deposits at the heads of the large
lakes (see Plate IV).

Ridges and Grooves

Perhaps the most prominent and striking glacial feature of the area
is the system of parallel, drumlin-like ridges and intervening grooves seen
so clearly in the air photographs (see Plate V). These ridges and grooves
mark the direction of the last ice advance in this part of British Columbia.
The general direction of the markings, which is north 50 to 80 degrees east,
agrees very closely with that of glacial striae measured on rock surfaces.
Valleys in some instances have influenced the direction of ice flow and in
such cases a change in the direction of the ridges may be noted. The
direction of many valleys is closely aligned with the principal direction of
ice flow so that the amount of influence the valleys exerted is difficult
to assess. There is no doubt that in the early stages they were the main
channels of ice flow and probably contained the ice until it became of

sufficient thickness to override the valley walls. Es