Introduction

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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18,000 Years BCE

The Cordilleran Ice sheet covers the majority of British Columbia, and is connected to the Western Laurentide over the Canadian Rockies.

17,500 Years BCE

Seams between the Cordilleran ice sheet and the Western Laurentide sheet appear in the northern part of what is now British Columbia and Alberta.

17,000 Years BCE

The southern end of the Cordilleran moves south during a period of glacial growth.

16,500 Years BCE

Both the Cordilleran and the Laurentide continue southern movment, pushing further into eastern Washington state.

16,000 Years BCE

The southern boundary of the Cordilleran Ice Sheet continues to grow, and around this time it is believed to have reached its greatest extent.

15,500 Years BCE

Glacial Lake Columbia, another ice-dammed lake, forms west of Glacial Lake Missoula.

15,000 Years BCE

A large portion of the Cordilleran ice sheet, called the Puget Lobe, extends south.

14,500 Years BCE

The Puget Lobe reaches its fartherst southern extent, and its erroding features create the inland waterway that becomes known as the Puget Sound.

14,000 Years BCE

A sliver of land is opened as the western Laurentide ice sheet grows apart from the Cordilleran.

13,500 Years BCE

Significant temperatures and climatic conditions accelerate the loss of glacial material, the Puget Lobe melts, and the Cordilleran and Laurentide sheets continue to move away from each other.

13,000 Years BCE

This gap continues to widen as the Cordilleran undergoes its most significant period of deglaciation.

12,500 Years BCE

At this time, the western Laurentide has become fully separated from the Cordilleran, opening a corridor of land between the two ice sheets.

12,000 Years BCE

The interior where the Cordilleran and Laurentid have separated is inundated with meltwater lakes.

11,500 Years BCE

Deglaciation trends continue, with increased separation, retreat and meltwater features.

11,000 Years BCE

The Cordilleran has lost a significant amount of material, opening more land for migration, and creating more lakes and eroding features.

10,500 Years BCE

Material is lost at an increasing rate, and the Cordilleran is fully isolated from the Western Laurentide.

10,000 Years BCE

The Cordilleran ice sheet has undergone a significant loss of material.

The landscape we see today

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.

Sources

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