The Georgia Depression is a depression in the

Pacific Northwest The Pacific Northwest (sometimes Cascadia, or simply abbreviated as PNW) is a geographic region in western North America bounded by its coastal waters of the Pacific Ocean to the west and, loosely, by the Rocky Mountains to the east. Though ...

region of western

North America North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and the Car ...

. The depression includes the lowland regions of southwestern

British Columbia British Columbia (commonly abbreviated as BC) is the westernmost province of Canada, situated between the Pacific Ocean and the Rocky Mountains. It has a diverse geography, with rugged landscapes that include rocky coastlines, sandy beaches, ...

and northwestern

Washington Washington commonly refers to: * Washington (state), United States * Washington, D.C., the capital of the United States ** A metonym for the federal government of the United States ** Washington metropolitan area, the metropolitan area centered on ...

along the shores of the

Salish Sea , image = PNW-straits.jpg , alt = , caption = The Salish Sea, showing the open Pacific Ocean at lower left, and from there, heading inland: the Strait of Juan de Fuca, the narrow Puget Sound at lower ri ...

Formation

The Georgia Depression was formed out of the collision of continental plates about 150 million years ago. During this period, the depression manifested as a broad valley with various rivers flowing down into it to reach the

Pacific Ocean The Pacific Ocean is the largest and deepest of Earth's five oceanic divisions. It extends from the Arctic Ocean in the north to the Southern Ocean (or, depending on definition, to Antarctica) in the south, and is bounded by the continen ...

where the mouth of the Strait of Juan de Fuca lies.Environmental History and Features of Puget Sound
, NOAA-NWFSC Much of the current topography was formed through the erosion of the depression by the Cordilleran Ice Sheet during the

Vashon Glaciation The Vashon Glaciation, Vashon Stadial or Vashon Stade is a local term for the most recent period of very cold climate in which during its peak, glaciers covered the entire Salish Sea as well as present day Seattle, Tacoma, Olympia and other surro ...

, which lasted from about 19,000 – 16,000 BP. The retreat of the ice sheet revealed a scarred landscape that filled in with sea water once it had retreated beyond what is now the Strait of Juan de Fuca, forming the

Geography

The Georgia Depression is encompassed by the

Pacific Ranges , photo = Mount Garibaldi (50997016501).jpg , photo_size = 280px , photo_caption = Mount Garibaldi massif as seen from Squamish , map = , map_image = South BC-NW USA-relief PacificRanges.png , m ...

to the north, Vancouver Island Ranges and

Olympic Mountains The Olympic Mountains are a mountain range on the Olympic Peninsula of the Pacific Northwest of the United States. The mountains, part of the Pacific Coast Ranges, are not especially high – Mount Olympus is the highest at ; however, the easter ...

to the west, and North Cascades to the east. The depression includes the Fraser Lowland, Nanaimo and Nahwitti lowlands of

Vancouver Island Vancouver Island is an island in the northeastern Pacific Ocean and part of the Canadian Provinces and territories of Canada, province of British Columbia. The island is in length, in width at its widest point, and in total area, while are o ...

, Puget Sound basin, and all the islands and adjoining waterways of the

. The majority of the population of

and

reside within this depression.

Geology

The landscape features glacially striated tablelands and rolling hills underlain by sedimentary rocks. The majority of soils in the depression are formed from glacial till,

glacial outwash An outwash plain, also called a sandur (plural: ''sandurs''), sandr or sandar, is a plain formed of glaciofluvial deposits due to meltwater outwash at the terminus of a glacier. As it flows, the glacier grinds the underlying rock surface and ca ...

, and

Lacustrine deposits Lacustrine deposits are sedimentary rock formations which formed in the bottom of ancient lakes. A common characteristic of lacustrine deposits is that a river or stream channel has carried sediment into the basin. Lacustrine deposits form in all ...

Ecology

Much of the Georgia Depression is dry, flat, and at low elevation relative to the surrounding highlands. As such, a wide diversity of flora and fauna thrive within the depression. Human activity has greatly altered much of the natural environment here through

industrialization Industrialisation ( alternatively spelled industrialization) is the period of social and economic change that transforms a human group from an agrarian society into an industrial society. This involves an extensive re-organisation of an econo ...

, agriculture, forestry, urbanization, and

suburban sprawl Urban sprawl (also known as suburban sprawl or urban encroachment) is defined as "the spreading of urban developments (such as houses and shopping centers) on undeveloped land near a city." Urban sprawl has been described as the unrestricted growt ...

References

''Landforms of British Columbia: A Physiographic Outline'', by S. Holland 1964 (revised 1976), British Columbia Ministry of Energy, Mines and Petroleum Resources ''Landforms of British Columbia: A Physiographic Outline''- ''Physiographic map'', by S. Holland 1964 (revised 1976), British Columbia Ministry of Energy, Mines and Petroleum Resourcesaccess to online ''Physiographic map of the Canadian Cordillera'', W.H. Mathews, Geophysical Survey of Canada (Natural Resources Canada), 1986
{{coord missing, British Columbia Landforms of British Columbia Landforms of Washington (state) Geography of the Pacific Northwest

Formation

Geography

Geology

Ecology

See also

References