4

The scouring action of the streams is tremendous at such times and great
quantities of coarse gravel and boulders are carried downstream annually
in this way.

During the last week in May 1936 exceptionally warm weather caused
very rapid melting of the snow on the mountains throughout the district
and resulted in the most serious flood ever known along Skeena river. The
big river rose 15 feet above its normal high-water mark and swept down
through all the towns and villages located along the water front from
Hazelton to tide-water. Many homes were destroyed, bridges were
damaged, and over fifty washouts along the railway enforced cessation
of train service for one and a half months.

The main valleys and lower mountain slopes are heavily forested with
a fine growth of hemlock, spruce, balsam, cedar, and poplar. The area is
well known for its cedar pole industry, some of the poles shipped from
Terrace being over 100 feet long. Timber-line extends to an elevation
of 4,500 feet.

GENERAL GEOLOGY

Terrace area lies along the eastern contact zone of the Coast Range
batholith, which occupies a belt 90 miles wide running in a northwest
direction along the Pacific coast. The east border of the batholith intrudes
a wide belt of Mesozoic volcanic and sedimentary rocks ranging in age
from Triassic to Cretaceous. The batholithic, volcanic, and sedimentary
rocks are intruded by a wide variety of dykes, including quartz albite,
aplite, diorite, gabbro, and lamprophyre dykes.

Table of Formations

Period Formation Lithology
Recent and Pleistocene....]...........------- Gravel, sand, silt, talus, boulder clay,
glacial drift.
Middle Dykes.
Cretaceous |......... SS
or Coast Range Granite, granodiorite, quartz diorite,
Later intrusives....... diorite, gabbro, etc.
Lower Cretaceous......... Skeena........... Shale, sandstone, conglomerate, coal.
Upper Jurassic Sedimentary division:
Sandstone, argillite, quartzite, grey-
Hazelton group.... wacke, slate, tuff, conglomerate.
Voleanic division:
‘ Andesite, breccia, tuff, rarely lime-
Lower Jurassic stone, argillite, and chert.
PPIASSICEHii5 css eosin sas | eeis selene tanta Cherty quartzite, argillite, crystalline
limestone, conglomerate.