— We propose three different hypotheses
to explain our terrace
elevation data along Lake Iliamna. Firstly, there may have been no crustal deformation (a)
during lake-level decline. This
hypothesis fails to explain a large section of coast where no profiles show scarps
as high as those further to the northeast. Secondly, isostatic rebound might have tilted the lake over
time (b) leading to older beaches being sloped along their length. Though along two large sections of
coast the uppermost scarp lies at roughly the same elevation, this might be
coincidental, and the true highest scarp may have been eroded away on many of
these profiles. However this
interpretation still fails to explain the location of the uppermost wave-cut
scarp on profiles 10 and 11. On
profile 10, our survey did not reach the highest beach feature, and yet the
hypothesis depicted here predicts it would. On profile 11 the uppermost scarp lies well below the
prediction, and the scarp is not tall enough to have removed some higher
scarp. Lastly, the terraces might
be roughly flat, but offset by localized deformation on or over an active fault
(c). This hypothesis can explain
all the data.
