Charles and Margo Wood - Charlie\'s Charts North to Alaska

17

circulation of water near the glacial snouts themselves is erratic, since fresh

vater is always being discharged and the ice movements are correspondingly

unpredictable. DO NOT APPROACH A~Y GLACIAL FACE CLOSER THAN 1/2 MILE. Treat

large icebergs with respect and pass well clear of thern. After having seen an

iceberg roll over it will be easy to appreciate the reason for caution.

Glaeial ice forms as snow crystals accumulate and are buried by successive
falls which slowly change the crystals by pressure, resulting in changes in
density and crystal structure (a volume decrease of as much as 9 times occurs).
The denser the ice, the bluer it looks since air has been e1iminated and the
greater proportion of water molecu1es present absorb alI co10rs except blue,
which i5 transmitted. Thus the color of the ice gives clues as to its origin
-- white bergs have much air stilI trapped and come from near the surface, blue
bergs are true glacier ice formed deep be10w the surface, greenish-black bergs
come from near the bottom of the glacier, and striped brown bergs show layers
of moraine sediments from the side of the glacier.

Ice presents a different and much greater prob1em in winter, when in

addition to glacier ice certain bays are subject to sea ice, and vesse1s can be

dangerously hampered by the aeeretion of superstructure icing. The majority of

vessels using this guide should be snug in harbor during such times.

Mirages

Mirages are not in themselves dangerous. They occur because of temperature

and density variations in the air and are found at the higher latitudes of this

guide particularly where the mountains and their snow and ice coverings help to

provide these conditions. Glaeier Bay provides examples of towering - the

vertical elongation of distant objects; and of superior mirage - the appearance

of an inverted image above an object. Looming may occur here as well as in any

part of the world. This results in objects appearing to rise above their

actual elevation to the extent that things below the horizon may come into view

long before one would expeet to see t~em. Exeept for their interest, mirages

ean be accepted mentally and accounted far in one's navigation.

~ind ChilI, Clothing, and H'pothermia

These are a very important eonsideration -- even in summer, when one is

travelling in areas cooled by weather, nearby snovy peaks, and glaciers. The

summer climate in the northern areas of this guide i5 te~perate and tolerable,

~ith daily mean temperatures in the mid 50's (F), and maximums that can be as

high as the 80's and 90's. But when cool ~inds blow ~ith temperatures in the

50's and 60's the effect of the wind chilI faetor is to make the conditions

equivalent to much colder temperatures.

Cool \.-inds can cause a considerable amount of body heat loss and strong

cold winds can lower body temperature by causing a los5 greater than the

replacement rate. As this eondition is affected by any barrier to the wind's

effect, the va1ue of a good dodger behind which to shelter and windproof

clothing combined with several layers of under clothing 15 obvious. Except

when the sun's rays beat directly down on calm day5 it is worthwhile to wear

one's heavy weather suit as an outer windproof covering with several layers

consisting of sweaters, flannel shirts, and longjohns underneath. Gloves are