Figure 5. How map unit types relate to a valley glacier. (After Boulton and Eyles 1979.)

Figure 4. Major landforms in the Anchorage Lowland.

Table 1. Characteristics of surficial deposits.

TR00-3
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8

Lateral Moraine

Active Lateral Moraine

Debris Flow (Diamicton)

Glaciofluvial Outwash

(Outwash Train)

Glacial Marine Silt

Diamicton (Till)

Figure 5. How map unit types relate to a valley gla-

cier. (After Boulton and Eyles 1979.)

ridge is relatively high on a mountainside, it may

across south-central Alaska. It indicates a major

regional advance between 14,000 and 13,000 14C

directly overlie bedrock. In other areas, they

appear laterally gradational with colluvium on

years BP (before present) (Reger et al. 1995). There

the mountain slopes while overlying other glacial

are also several smaller end moraines in the larger

valleys of the Chugach Mountains (Schmoll et al.

Ground-moraine deposits

Ground moraines form through a number of

Lateral-moraine deposits

processes believed to operate beneath glaciers,

These deposits develop as narrow, well-defined

most of which are not fully understood (e.g.,

ridges and less well-defined ridge segments along

Drewry 1986, Menzies and Shilts 1996). They are

the sides of glaciers. Lateral moraines are com-

spatially extensive and commonly thinner than

posed of sand, gravel, and diamicton, similar to

deposits of end and lateral moraines (e.g., Fig. 4

end moraines (Fig. 5; Plate 1). Lateral moraines are

and 5; Plate 1). Ground moraines may be associated

found in the Chugach valleys and along the

with positive-relief landforms, such as flutes and

Chugach Mountain front. The latter ridges are

drumlins. They are generally composed of diam-

aligned in an en-echelon pattern, descending

icton that may exhibit various degrees of sorting

gradually to the southwest. Older moraine ridges

and stratification and may contain thin, inter-

are generally better developed in the southwest,

bedded sand, silt, and gravel horizons. These de-

where they form the principal ridges along the

posits are common north of the Elmendorf

base of the Chugach Mountains (Schmoll et al.

1996). Lateral moraines usually have gentle to

Moraine, where there are many drumlins and the

moderate slopes along ridge tops, but steep sides,

surface is locally incised by modern and ancient

especially in the downslope direction. Where a

alluvial channels and are of similar age to the

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