South American Archaeology: Northwest Landscapes

Northwest Landscapes

Overview of Northwest post Pleistocene regional geography and vegetation communities
1. Pacific Province
  1. Olympic peninsula
    1. West coast, narrow and rocky
      1. Continental shelf
    2. Olympic Mountains, very high and craggy
      1. Maximum Elevation 7,950 ft. asl
    3. Rain forest, giant cedars, mossy understory
      1. Annual precipitation 120-140 inches/year
    4. Drained by short rivers
      1. Quinault
      2. Elwah
      3. Hoko
  2. Pudget trough (northern part inundated: Pudget Sound southern part valleys of Chehalis, Cowlitz, and Columbia rivers)
    1. Structural trough
    2. Many islands and rocky protuberances
    3. Maritime forest, Douglas fir and cedar
      1. More open meadows in the past, formerly maintained by aboriginal burning
      2. In the rain shadow of the Olympic Mountains, Seattle average 37 inches/year precipitation
  3. Southern Washington/Oregon Coast (Willapa Hills)
    1. Wider, sandier beached coast than on peninsula
      1. Major indentations: Grays Harbor, Willapa Bay
    2. Lower, less rugged mountains, 3,000 ft. asl
    3. Less densely forested
  4. Tide cycle very important
    1. Most and least areas of exposure twice each month
    2. Very most exposed December and June, equinoxes
2. Sierra-Cascade Province
  1. Volcanic origin, including active volcanos
    1. Rugged mountain 6,000-8,000 ft. asl
    2. Tallest volcanoes (important for tephrochronology)
      1. Mt. Rainier 14,410 ft.
      2. Mt. Adams 12,276 ft.
      3. Mt. Baker 10,778 ft.
      4. Mt. St. Helens 8,365 ft.
      5. Glacier Peak 10,541 ft.
        
        Significant areas above tree line
        
        Some modern glaciers
  2. Low elevation passes
  3. Western slopes of Cascades
    1. Dense maritime forest, Douglas fir and cedar
    2. Many short rivers, streams, and lakes
  4. Eastern slopes (lumped with Columbia Plateau because of climate rather than land form)
3. Columbia Plateau province
  1. Eastern slopes of Cascades
    1. Drier, 15 inches/year
    2. Open Ponderosa pine forest, white pine at higher elevations
    3. Short, but big rivers
      1. Yakima
      2. Methow
      3. Wenatchee
      4. Stehekin/Lake Chelan
  2. Okanogan Highlands
    1. NxS trending ridges shaped by continental glaciation
    2. Drier parkland forests and grasslands
    3. Major rivers, Okanogan and Sanpoil
  3. Columbia Basin
    1. Center 300 feet about sea level
    2. Before irrigation, desert 6 inches/year
      1. Hot summers, cold winters
    3. Native vegetation big sage brush and blue bunch wheat grass
    4. Really big rivers
      1. Columbia River
      2. Snake River
    5. Terrain largely shaped by Pleistocene floods
  4. Palouse
    1. Ancient lava flows covered all but tallest pre-miocene mountains
      1. Remnant mountain tops include Steptoe and Kamiak Buttes
    2. Wind blown miocene loess
    3. Moderate precipitation, 12-16 inches/year
    4. Grasslands with Ponderosa pine on north facing slopes of stream valleys and brushy valley bottoms and some hill slopes
    5. Beyond the reach of pleistocene floods
    6. Smaller rivers and lakes, Palouse River and seasonal tributaries
  5. Blue Mountains, very southeastern Washington and north eastern Oregon
    1. Different ranges with different orientations
    2. Moderate slopes
    3. One major river, Grande Rhonde
    4. Xeric forest
4. Northern Rocky Mountain Province, very easternmost Washington, northern Idaho, and northwestern Montana
  1. Mesic forest: Hemlock, cedar and larch in addition to Douglas fir, White pine, Ponderosa Pine, lodgepole pine
  2. Major Rivers: Kettle, Pen Oreille, Colville, Kootenai, Clark Fork

Video: Over Washington
This is a 50 minute video produced by a tourism group in Washington State. The images are largely taken from low flying aircraft and there is no dialogue, just airy music. I also bring to class a large, 4x5 foot, beautiful, laminated topographic map of Washington (made by Raven Maps in Oregon) that I hang on the white "write-on" board with magnets. I actually bring the map to every class, sometimes I refer to it a lot sometimes it just hangs there and hopefully gives the students a sense of the region we are talking about. As the video introduces different geographic areas of Washington I stop the machine and identify the region presented by the video on the map. I also often speak over the music to point out things or expand on things in the video. This is a little bit of an awkward presentation but the visuals can do what words can't and the video is the best overview I have found to date. In fact it was given to me by a student in a former class.

Landscape history, associated with glaciation, last major period of glaciation
1. Wisconson 100-10 KYA
  1. Not one big advance and then retreat but multiple advances and retreats
2. Last advance—Fraser Advance
  1. Began about 20 KYA
  2. Reached maximum 18-16 KYA
    1. Continental and alpine ice sheets
  3. About 14 KYA de-glaciation began
    1. 11-9 KYA ice retreated to mountains
3. Alpine glaciers continue to advance and retreat (but no continental ice)
  1. Three notable periods of glacial advance since the end of the "Ice Age;" related to cooler/moister climatic episodes.
    1. About 7 KYA
    2. About 4.5-2 KYA ("Neoglacial")
    3. 500 years ago to early twentieth century ("Little Ice Age")
      1. Since 1940s glaciers melting
4. Washington Coastline not glaciated during late Wisconson
  1. Pudget Sound—Strait of Juan de Fuca glaciated
  2. Olympic mountains glaciated
  3. Cascades glaciated
5. Coastline not glaciated but still effected by glaciation
  1. Water tied up in ice, sea level lower. At maximum 320-500 ft. lower than present
    1. Continental shelf exposed, average about 25 miles wide (overhead)
  2. Glaciers also resulted in isostatic changes, ie., land surface rising and lowering
    1. Heavy ice weighs down land masses beneath and adjacent to it
      1. Pushes more distant areas up
      2. Process reverses when ice melts, ie., lands beneath and adjacent to ice rise, more distant lands lower
  3. Results in complex local effects, ie., individual locations can have complicated historic of submersion and exposure
    1. Isostatic changes slower than water level changes
  4. Further complicated by tectonic activity, ie., moving plates, as in continental drift and earthquakes
  5. The modern coast line is only about 2,000 years old and local changes still taking place
6. Interior
  1. Continental ice sheet over Okanogan Highlands to south of Spokane
  2. Alpine glaciers in Cascades, Blues, Rockies
  3. Major landscape altering events toward the end of the Wisconson period
    1. Spokane (or Missoula floods)
      1. Idea first proposed by J. Harlin Bretz
        
        University of Chicago, 1920s
        
        Not accepted until 1960s-1970s
      2. Others recognized lake deposits
        
        Well bedded/sorted sands and silts
        
        Interpreted them as representing a large, long-lived, proglacial lake
      3. Underlying theoretical issues
        
        Gradualism vs catastrophism

15 minute video, "The Great Floods" Produced by WSU in cooperation with the Coulee Dam National Recreation Area and the National Park Service. Very good film, good aerial photos of landscape features formed by the floods and computer graphics that show the extent of the ice sheets and flood events.

Post glacial environments, climate and vegetation
1. Sources of information
  1. Plant remains
    1. Pollen
    2. Macrofossils
    3. Bog cores and soil profiles
  2. Animal remains
    1. Large animals
    2. Small animals, sometimes especially sensitive to change
    3. Fresh water shell fish
      1. Different species with different water conditions
        
        Fast vs slow flow
        
        Clear versus silty
        
        Warm versus cold
  3. Geomorphology, especially fluvial (ie. water deposits)
    1. Streams and rivers form deposits and erode materials at the same time, young rivers move around a lot as they cut a channel, once channel is defined movement slows but never stops
    2. Size and character of sediments
    3. Amount of water in the system
    4. Timing of maximum flow
    5. Type and amount of stream\river side vegetation
  4. Soil types and distribution
    1. Different types of soil result from different factors (not silt, loam etc. but forest soils, grassland soils, bog soils, etc.)
      1. Parent material
      2. Type of plant material
      3. Amount of water
Reconstructed climate/vegetation/faunal histories
1. Coast
  1. Fewer forested areas during height of glaciation
    1. Grasslands, parklands, tundra
  2. Forests expand at end of glaciation, about 14 KYA
    1. Early species lodgepole pine, within 2,000 years more varieties of pine and fir (so 12KYA or so)
  3. Faunal remains poorly preserved, but maybe elephants (Manis mastadon)
  4. 10-7 KYA
    1. Rapid warming
    2. Declining rainfall, especially during summer
    3. Grasslands expand, dry tolerant tree expand area (oak, Douglas fir) moisture loving trees decline (spruce, hemlock)
    4. Higher proportion of sea than land mammals, especially seal; land mammals include elk and deer; also salmon and other fish as well as mussels
  5. 7-4 KYA
    1. Temperature and precipitation increase
      1. Probably warmer than today, but maybe also moister, or at least as moist as today
      2. Forest composition changed again, to moisture loving trees, cedar by 5-3 KYA
    2. Faunal assemblage similar
  6. Late Holocene, changes still on-going, but more localized; plant communities especially, shifting
    1. Relative proportion of different species
    2. Distribution of different species
    3. Greater amount of shellfish, but maybe technological/cultural change rather than environmental change but is more or less coincident with "stabilization" of modern coastline so may have allowed growth of shellfish beds
2. Interior
  1. 11-9.5 KYA
    1. Warm dry summers, very cold winters
      1. Young big rivers, cutting through glacial outwash, sandy, shifting river beds
      2. Fewer trees, more grasslands
      3. Faunal assemblages include elk, bison, deer, mountain sheep, and pronghorn
  2. 9.5-6.5 KYA
    1. Increased moisture in mountainous areas
      1. Increased number of trees
    2. Drier in Okanogan highlands and basin
      1. Grasslands declined, sage communities expanded
      2. More aeolian activity (drier, less plant cover, more wind erosion)
      3. Pronghorn antelope population increased
  3. 6.5-4.5 KYA
    1. Evidence for cooling but still warmer than present
    2. Decreased aeolian activity
    3. Tree lines lower (ie., forest expanding back into grasslands)
  4. 4.5-2.5 KYA
    1. Coolest and wettest period of the holocene
    2. Continued forest expansion
    3. Winter dominant precipitation, cooler summers and winters
  5. 2KYA
    1. Warmer, especially warmer summers
    2. Grasslands expand, forests shrink, also different balance of tree species
    3. Bison "common" only time during pleistocene
    4. (Still make up only about 10% of faunal assemblages)
    5. Modern river channels established
    6. Forest fires more frequent, maybe associated with human activity
  6. Summation
    1. Although there are regional generalizations, such as those mentioned above, most changes were predominately localized, eg., once different plant communities had colonized the region the relative balance changed in response to climatic changes but whole new species did not appear and disappear; change could be fast, a decade or so