The topography, climate, and vegetation of the Pacific Northwest, its fjords, inland waterways and islands, are a result of an extended period of glaciation and glacial retreat.
This retreat influenced the physical features and the resulting succession of vegetation that led to the landscape we see today.
This tool takes the user through an interpretive, interactive journey of the deglaciation events.
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The Cordilleran Ice sheet covers the majority of British Columbia, and is connected to the Western Laurentide over the Canadian Rockies.
Seams between the Cordilleran ice sheet and the Western Laurentide sheet appear in the northern part of what is now British Columbia and Alberta.
The southern end of the Cordilleran moves south during a period of glacial growth.
Both the Cordilleran and the Laurentide continue southern movment, pushing further into eastern Washington state.
The southern boundary of the Cordilleran Ice Sheet continues to grow, and around this time it is believed to have reached its greatest extent - between approximately 2,741,591 and 2,749,954 sq. kilometers.
Glacial Lake Columbia, another ice-dammed lake forms in this peris west of Glacial Lake Missoula. Occasional dam breaks result in floods that scour Eastern Washington.
A large portion of the Cordilleran extends into what is today known as the Puget Sound. This formation is called the Puget Lobe. Glacial dams on the Southeast extent of the Cordilleran break allow meltwater to accumulate, forming Glacial Lake Missoula.
The puget lobe reaches its fartherst southern extent, and its erroding features create the inland waterway that becomes known as the Puget Sound.
A sliver of land is opened as the western Laurentide ice sheet grows apart from the Cordilleran. Multiple glacial lakes form from the meltwater.
Significant temperatures and climatic conditions accelerate the loss of glacial material, and the Puget Lobe melts. A gap between the Cordilleran and Laurentide sheets widen as they move away from each other.
This gap continues to widen as the Cordilleran undergoes its most significant period of deglaciation. It lost approximately 700,000 sq. kilometers over the thousand years between 13,000 BCE and 12,000 BCE.
At this time, the western Laurentide has become fully separated from the Cordilleran, opening a corridor of land between the two ice sheets. It is theorized that the first human visitors to North America may have used this route (alongside coastal routes) to access the continent's interior.
The interior where the Cordilleran and Laurentid have separated is inundated with meltwater lakes.
Deglaciation trends continue, with increased separation, retreat and meltwater features.
The Cordilleran has lost a significant amount of material, opening more land for migration, and creating more lakes and eroding features.
Material is lost at an increasing rate, and the Cordilleran is fully isolated from the Western Laurentide. The large glacial meltwater lakes between the two become scarce and begin to disappear. The landscape increasingly appears to resemble what is seen today.
The Cordilleran ice sheet has undergone a significant loss of material. It has an approximate 500,000 square kilometers of disconnected glacial material remaining, mostly focused in the Coast and Rocky mountains.
The landscape we see today was directly influenced by these series of growth and retreat. It is what gives this region its geographic and biological diversity, and these great changes were a result of climatic factors. This landscape can still change further.
Data:
Elsevier: Ehlers, Gib0bard, Hughes: Quaternary Glaciations - Extent and Chronology Volume 15
Natural Earth
Other:
Whitlock, C. (1992). Vegetational and climatic history of the Pacific Northwest during the last 20,000 years: Implications for understanding present-day biodiversity. The Northwest Environmental Journal, 8:5—28. Retrieved February 11, 2019, from https://www.fs.fed.us/rm/pubs/rmrs_gtr292/1992_whitlock.pdf