Figure 15. Map of part of south-central Alaska showing present-day extent of glaciers and icefields.

Figure 16. Map of south-central Alaska showing possible maximum extent of glacial ice during the most recent major glaciation (the late Wisconsin, about 26,000 to 10,000 radiocarbon years ago). Glaciers probably covered a smaller area of the continental shelf than shown here. Some areas of the continental shelf may have been free of glacial ice and exposed as land by lower sea level. Such lands probably supported herb and shrub tundra vegetation and probably some bird, mammal, and fish populations. Green areas indicate ice-free regions or "islands."

Figure 17. Extensive ice fields exist today in the Kenai Mountains, Chugach Mountains, St. Elias Range, and Wrangell Mountains of south-central Alaska (see Fig. 15). In this photograph, part of the massive Malaspina Glacier is shown flowing south from icefields in the western St. Elias Range, east of the area shown in Fig. 15. The sinuous ridges shown on the glacier surface in the foreground are medial moraines covered by late winter snow. This photograph helps us visualize what the southern margins of the icefields of south-central Alaska looked like during Pleistocene glaciations. T. Ager photo.

Figure 18. Present-day tidewater glaciers of south-central Alaska can be found in Prince William Sound and southern Kenai Peninsula. Icebergs form as portions of the glacier terminus collapses. Modern tidewater glaciers in Alaska are very small in comparison with massive glaciers that reached the sea during full glacial time (see Fig. 16). T. Ager photo.

Figure 19. Boreal forests occupy the valleys of "interior" south-central Alaska such as the upper Nenana River valley, shown here. These forests include white spruce, black spruce, paper birch, aspen, balsam poplar, alders, and willows as major tree and shrub types. These forests now occupy valleys that were filled with glacier ice or glacial lakes during the last major glaciation. Boreal forests spread from interior Alaska (north of the Alaska Range) into south-central Alaska following the retreat of glaciers. T. Ager photo.

Figure 20. A peat core from this black spruce bog near the Anchorage airport provides a pollen record (and vegetation history) of the upper Cook Inlet dating back to about 11,500 radiocarbon years ago. T. Ager photo.

Figure 21. Circle Lake formed as a kettle pond on a lateral moraine on the north side of Kachemak Bay, Kenai Peninsula. A sediment core provides a pollen record and vegetation history for the past 12,800 radiocarbon years. The present-day vegetation around Circle Lake is primarily boreal forest, but some coastal plants also grow nearby. The spruce trees growing around the lake appear to be hybrid white spruce-Sitka spruce. T. Ager photo.

Figure 22. Subalpine and alpine zone vegetation on the north flank of the Chugach Mountains shows scattered, stunted white spruce trees interspersed with shrubs such as alders, willows, and blueberries. Rounded mountain summits and glacially sculpted landforms indicate that this part of the valley was overridden by glacial ice during the late Wisconsin glaciation. A peat core near this location provides a pollen record and vegetation history for the past 9300 radiocarbon years. T. Ager photo.

Figure 23. Alpine tundra vegetation in the Chugach Mountains is adapted to short, cool growing seasons and thin to rocky soils. Alpine tundra plants survived in scattered ice-free areas of south-central Alaska during past glaciations. T. Ager photo.

Figure 24. Alder thickets with an understory of ferns cover extensive areas of coastal south-central Alaska. Pollen records indicate that this vegetation colonized much of the region between 10,000-9300 radiocarbon years ago. In many areas of coastal south-central Alaska this vegetation type was replaced by coastal forest within the past ca. 3000 years. T. Ager photo.

Figure 25. Coastal forests of south-central Alaska commonly are composed of Sitka spruce, and mountain hemlock, with black cottonwood in some valleys. In Prince William Sound and areas to the east, western hemlock and yellow cedar are also part of these forests. This photo shows a small sedge-moss bog near Girdwood, NE Turnagain Arm, surrounded by mountain hemlocks. T. Ager photo.

Figure 26. In general, trees in the coastal forests of south-central Alaska rarely grow to the impressive diameters seen in southeastern Alaskan old growth forests. However this Sitka spruce and many others of similar size were found on western Hinchinbrook Island in Prince William Sound in 2003. T. Ager photo.

Figure 27. Muskegs are wet, peaty areas that cover large areas of flat to gently sloping terrain in southern and southeastern coastal Alaska. The high water table and low nutrient content of the peat create unfavorable conditions for tree growth. Trees that grow in muskegs are usually stunted, malformed, and slow-growing, such as these mountain hemlock "trees" on Hinchinbrook Island in Prince William Sound. T. Ager photo.

Figure 28. A coastal exposure of peat overlying silt and glacial till is being eroded by high tides and storm waves. Samples from this exposure provide a pollen record and vegetation history for northern Hinchinbrook Island spanning more than the past 10,000 years. Eroding peat deposits such as this can be found in numerous coastal locations in Prince William Sound. This indicates that coastal lands are undergoing subsidence in many areas. P. Carrara photo.