Park Point beach, April 11, 2003
Ice by any other name?
Learn the different words used to describe ice and snow by both Inuit and English speakers.
Candled ice on
Park Point beach
Is that why it's Colder by the Lake?
One of the most pleasurable things to do on a sunny spring
day in Duluth is to go down to the beach at Park Point and
wander the Lake Superior shoreline when the winter's ice floes
are stacked up. Some years a strong Northeast wind will stack
the winter's lake ice into piles 5 or 10 feet or more, forming
a wonderful maze of ice, snow, gouged up sand and pools of
crystal clear water.
The ice itself appears in a striking variety of clear and frosted
slabs, needles and flakes. In Winter 2002-2003, after a relatively
snowless (until Spring at least) but fairly cold winter, the
big lake froze over about 95% of its area (see image below).
Lake Superior freezes at least in part every year and less frequently
in its entirety. The last year that it froze completely was
in February 1994. It almost froze completely in March 2003 and
this photograph was taken by the GOES satellite on March 7,
It is one of a series taken from 17 February - 18 March 2003
during a cold spell in the northland when ice was forming
on Lake Superior. This image was taken from the
GOES Satellite Gallery
developed by the University of Wisconsin.
April 3, 2003. The Indiana failed to get out of the channel. Image courtesy of Duluth
After the weather warmed in early spring, strong winds from
the northeast that persisted for several days blew enormous
numbers of ice floes into the far western end of the lake where
it piled high from eastern Duluth all the way to the beach at
The ice piled so thick that on April 3, 2003 the thousand footer
iron ore boat Indiana was unable to break out of the Harbor
into Lake Superior. It did apparently manage to destroy our
water quality data cable connection to our website. The Coast
Guard cutter Mackinaw spent the next couple of weeks trying
to create and maintain a shipping channel.
Inactive fingerrafting highlighted by new snowfall. Lakewood, MN February 1970.
Finger Rafting and Pressure Ridges
Many strange shapes can be seen in lake and river ice. Rafting
refers to the process commonly seen in Duluth region lakes and
streams where pressure caused by expanding and contracting ice
causes one piece of ice to override another. It most commonly
occurs in younger, thinner ice.
Fingerrafting occurs when interlocking thrusts are formed,
each floe thrusting "fingers" alternately over and
under each other. Professor John Green of the University of
Minnesota, Duluth, noted these formations along the Lake Superior
shoreline just north of town in the 1960's and reported his
observations in a research journal (Green. J.C. 1970. Finger-rafting
in fresh-water ice: Observations in Lake Superior. J. of Glaciology
9(57) 401-404). He noted that the phenomenon occurred
when the ice was very thin (less than about 3/4 of an inch)
and could be caused by a gentle breeze. The image at right
is an example.
Ridging is the process where ice is formed into ridges. A
ridge is a line or wall of broken ice forced up by pressure.
The submerged volume of broken ice under a ridge, forced downwards
by pressure, is termed an ice keel.