The Fraser Glaciation lasted for about 10,000 years.  The ice that entered the Puget Sound occurred during the Pleistocene era.  The glacial occupation of the Puget Sound region is called the Puget Sound Lobe.  The advance began in the Olympic Mountains and was the beginning of the first stade: the Evans Creek Stade. At that time the ice divided going into the Strait of Juan de Fuca and Puget Sound.  The next stade was the Vashon stade, which reached its peak 15,000 years ago. This stage was much shorter and ended around 13,500 years ago.  To view the Glacial and Interglacial cycle view this link: http://www.nps.gov/olym/glacier/glaciate.htm

Evans Creek Stade:

     The maximum extent of this stage was reached at about 21000-19000 years B.P. (before present).  The glacier may have extended at its fullest to the Puget Sound Lowlands.  The Evans Creek Stade produced protracted alpine glaciation.  This type of glaciation is where the ice was formed in the Cascade and Olympic Mountain Ranges, which formed glaciers in the valleys.

Vashon Stade

     This Stage of Fraser Glaciation began in British Columbia and spread towards the area we now know as Issaquah near Snoqualmie Pass.  In the Issaquah area the glacier is thought to have reached a maximum thickness of about 3,000 feet!  As the Vashon Glacier retreated there were five main stages of ice stagnation that formed the topography (surface features) that exists today.  Five main stages of this retreat were (from oldest to youngest):

1. The glacier still occupied present day Lake Sammamish and as it melted drainage took place through Issaquah Creek and Tibbetts Creek.

2.  Lake Sammamish was formed and melting from Issaquah Creek was deposited into the newly formed lake.  Drainage out of the lake went through Tibbetts Creek.

3.  A large delta formed in the North Fork of Issaquah Creek and drainage out of Lake Sammamish occurred through what is now I-90.  Formation of the edges of the lake were happening along the eastern shore.

4.  Lake was much larger than its present size and occupied all of the lower Issaquah Valley.

5.  A low delta formed from 100-150 feet above sea level just south of present day Issaquah   

Tokul Delta Stage

Inglewood Stage

Redmond Channel Stage

Endemic Species are those which are unique to a particular area and are not found anywhere else in the world.  The Fraser Glaciation had a large impact on plants and animals in limiting their habitat ranges with its glacial advance.  Most of the affected endemic species are found only on the Olympic Peninsula and in the Olympic Mountain Range.

Endemic Plants  

• Olympic Mountain milkvetch Astragalus australis var. olympicus
• Piper’s bellflower Campanula piperi
• Flett’s fleabane Erigeron flettii
• Thompson’s wandering fleabane Erigeron peregrinus peregrinus var. thompsonii
• Henderson’s rock spirea Petrophytum hendersonii
• Olympic Mountain Groundsel Senecio neowebsteri
• Olympic Mountain synthyris Synthyris pinnatifida var. lanuginosa
• Flett’s violet Viola flettii

Endemic Animals

mammals: 

• Olympic Marmot Marmota olympus
• Olympic yellow-pine chipmunk Tamias amoenus caurinus
• Olympic snow mole Scapanus townsendii olympicus 
• Olympic Mazams pocket gopher Thomomys mazama melanops
• Olympic ermine Mustela erminea olympica 
    
  amphibians:  
• Olympic torrent salamander Rhyacotriton olympicus 
   
  fish: 
• Olympic mudminnow Novumbra hubbsi 
• Beardslee rainbow trout Oncorhynchus mykiss irideus 
• Crescenti cutthroat trout Oncorhynchus clarki clarki
   
  insects: 
• Hulbirt’s skipper Hesperia comma hulbirti 
• Olympic grasshopper Nisquallia olympica
• Mann’s gazelle beetle Nebria danmanni
• Quileute gazelle beetle Nebria acuta quileute
• Tiger beetle Cicindela bellissima frechini
   
  mollusks: 
• Arionid slug Hemphillia dromedarius
• Arionid jumping slug Hemphillia burringtoni

Featured Endemic Species

     The species of particular interest to the Vashon Stade of the Fraser Glaciation is the Olympic Mudminnow (Novumbra hubbsi).  The Olympic Mudminnow reaches a maximum length of only 8 cm.  Today there are only four species of the Mudminnow in existence.  There are two found in the Eastern US, 1 in Central Europe and 1 that exists in the area once covered by the Vashon Glacier.  The possible reasons that the Olympic Mudminnow has such a limited distribution are mainly due to glaciation.  During the Fraser Glaciation the Vashon Glacier all of the river systems became non-existent.  After the retreat of the ice sheet the Mudminnow had developed specialized behavioral preferences it was unable to leave its limited habitat range.

Olympic Mudminnow 

The Fraser Glaciation lasted about 10,000 years, a short time based on the history of the Earth.  In this relatively short time period, the cycle of glaciation has resulted in the formation of many of the large lakes in the Pacific Northwest.  Also, it limited the habitat range of a number of species of plants and animals giving this region the privilege of being the home to a number of endemic species.

Links

http://www.nps.gov/olym/invendemic.htm

http://www.nps.gov/olym/glacier/glaciate.htm

http://www.nativefish.org/Articles/Olympic.htm

http://www.front-street.com/COMORG/gwac/Glac.htm

http://www.front-street.com/COMORG/gwac/Stage.htm

http://courses.washington.edu/fish497u/week1.html