Lower Mainland Geology

Viewed geographically Greater Vancouver straddles the Coast Mountains and the Fraser lowlands of southwest B.C. While the region’s geology is a record of events that shaped the earth’s subsurface over millions of years, the soil reflects natural forces that left an imprint on the earth’s surface over the past 10,000 years: both cast the blueprint for settlement and development.

Over millions of years southwest British Columbia was formed by global movement which stacked slabs of the earth’s crust against each other. More than 150 million years ago igneous, granitic rocks were formed by the intrusion of hot, molten rock deep in the earth’s crust. More than 80 million years ago the Coast Mountains to the north and west of Vancouver were formed as the granitic rocks progressively were buoyed up in the earth’s crust. At the same time the Georgia basin formed between the mountains and what was to become Vancouver Island. Greater Vancouver was formed from sediments deposited approximately 35 million years ago in the younger part of the Georgia basin.

Some 2.5 million years ago when global cooling caused the formation of ice sheets in the Coast Mountains, glacial streams flowed out and over the Greater Vancouver area. When the last ice age began approximately 25,000 years ago, ice streams sculpted the area’s landscape. An ice sheet over Greater Vancouver perhaps two kilometres thick deposited a mixture of clay, sand and rock fragments, known as till, on the lowlands.

Until the end of the last ice age approximately 14,000 years ago, Greater Vancouver was submerged below sea level by the great weight of ice. When the ice eventually vanished about 11,000 years ago the sea invaded much of the Lower Mainland while the earth’s crust gradually emerged from the sea. At the same time great volumes of melting ice water flowed from the mountains and the Interior. Sediment carried down the Fraser River formed an estuary of sand, gravel and mud, which fanned westwards into Georgia Strait.

The process continued. Sediment from the Fraser River delta slowly built and continues to build outwards into Georgia Strait. Richmond and Delta are among the habitable areas formed by such sedimentary deposits. As land rebounded from beneath the sea, a weathering process created Greater Vancouver soils from glacial till, sand and clay. As the climate warmed, superior forests grew in well-drained soil.

Aboriginal groups first formed coastal communities around accessible fish, berries and timber. When European pioneers arrived in the mid-19th century, most of Greater Vancouver was covered by old-growth forest. Grasslands, shrubs and peat bogs covered the Fraser delta.

Settlers who came by boat organized communities close to inlets and creeks which offered safe anchorage, fish and timber. Since cities traditionally grow outwards from an industrial core, areas first to develop have superior soil and access to good timber. Steveston, Burrard Inlet, False Creek and New Westminster developed naturally from geological patterns. New Westminster was an ideal first capital city; situated on the Fraser River, near the upper limit of navigation for seagoing ships, it was easy to defend and close to rich timber resources.

Communities such as Kerrisdale grew around fertile, well-drained soil, accessible by rail and road. As land prices rose many farms and market gardens were swallowed by housing, shopping, schools and recreational facilities. Automobile transport allowed settlers access to other fertile soils which developed as integral communities east and southeast of the original city core.

Greater Vancouver’s natural soils have been modified over the years as timber was cut and roads and houses were built. Soils continue to be modified and amended by the planting of non-native species of plants and trees and where construction debris is used as fill. For example, after the natural soil of False Creek was contaminated by industrial waste, it proved an expensive undertaking to revert to natural soil conditions. Many remaining patches of natural soil in Greater Vancouver are in parks which are left in a near-natural state. Stanley Park is a notable example.