Vashon Glaciation

The Quaternary Glaciation is part of the Late Cenozoic Ice Age, which began 33.9 million years ago and is ongoing.

It was an ice sheet covering much of Canada, and parts of the northern United States in the Midwest and east.

This would seem to be a climate too warm to support glaciers, but the ice was pushing in from the north faster than it could melt.

However, 19,000 years ago marks the approximate time when glaciers crossed the present-day Canada–United States border into Western Washington,[6] which is generally considered to be the beginning of the Vashon Glaciation.

During the Vashon Glaciation, the Cordilleran Ice Sheet grew and advanced southwards at a rate of about 135 metres (443 ft) per year.

[6] The Puget Lobe reached its maximum extent in the vicinity of the present-day city of Tenino[9] around 16,950 BP.

[7] Around 16,850 BP, the Puget Lobe began retreating northward at a rate of about 340 meters (1,120 feet) per year.

[6] By about 16,000 BP, the Puget Lobe retreated far enough north that Glacial Lake Russell and the Strait of Juan de Fuca became connected, making Glacial Lake Russell the salt water body of Puget Sound again.

Around 16,850 BP when the glacier began retreating, the ice dam holding back the lake became breached causing a major glacial outburst flood.

[11] Bison antiquus[12] Panthera atrox[16] Smilodon fatalis[citation needed] Thomomys mazama melanops[18] Abies lasiocarpa[3] Picea engelmannii[3] Artemisia[3] Pollen data collected from Battleground Lake shows that between 16,000 and 15,000 BP, temperatures were around 4 ± 2 °C (7.2 ± 3.6 °F) colder than present (present as of 1990).

[3] From about 14,000 to 12,000 BP, more Pinus contorta (lodgepole pine) began to grow in the region, but was still an open area.

[3] The vegetation was similar to today with Alnus rubra (red alder), Picea sitchensis (sitka spruce), Pinus contorta (lodgepole pine), Pseudotsuga (Douglas fir), and Tsuga heterophylla (Western hemlock).

[3] Between 9,500 and 5,000 BP, there was Alnus (alder), Pseudotsuga (Douglas fir), Pteridium (bracken fern), and high amounts of Chrysolepis (chinkapin) and Quercus (oak trees).