Geoscience Reports
Winter 1986/87 No. 8
Glaciers: A Progeny of Earth's Climate
Introduction
What is a glacier? Where did it come from? How does it affect me
today, and what can it tell me about yesterday and tomorrow? The answers to these and
other questions lead us into another fascinating chapter of our Earth Series.
In the strictest sense a glacier is a large body of ice moving slowly
down a slope or valley. However, such a definition does not begin to describe the
intriguing natural phenomenon known as a glacier.
Glaciers are dynamic entities that currently cover about 10% of the
earth's land surface (see Table 1). They are found on every major land mass except
Australia, with the largest concentrations located at the earth's polar regions. While
glaciers contain 3% or less of the earth's total water, they contain up to 80% of the
earth's fresh water!
Glacial Budget
An active glacier is composed of two principal parts, an area of
accumulation and an area of ablation (wastage). The accumulation area is characterized by
yearly snowfall exceeding yearly snow melt, whereas the ablation area is characterized by
the yearly snow melt exceeding the yearly snowfall. Generally these two areas are
separated by the Firn Limit or Annual Snow Line.
Like you and me, glaciers are subject to budgets, environment and
gravity. Budgets, you say? Yes, budgets! However, the budget of a glacier is measured not
in terms of dollars gained and lost but in terms of snowfall and snow melt.
The glacier's budget period is seldom the same length or time every
year. A budget period has an accumulation sequence and a wastage sequence. The beginning
of a new budget period is defined as that point where accumulation of new snow exceeds
wastage of older material. The budget period extends through the following ablation
sequence up to the next accumulation sequence.
Unlike most, the glacier puts forth great effort to maintain a balanced
budget. In times of surplus the glacier expands down the valley, and in times of deficit
the glacier contracts and retreats up the valley in order to maintain a balanced budget.
It is very unlikely that within a single year a glacier could be found
to have a balanced budget. However, over a period of 5 to 10 years a small glacier can
maintain a balanced budget.
Formation of Glaciers
The ancestor of the mighty glacier is the delicate unassuming
snowflake. Immediately upon falling to the ground the snowflake begins to change
characteristics. Through the processes of melting, sublimation, crushing and compaction,
thousands of tiny snowflakes are formed into small granules of ice. This initial process
takes only a few days or weeks at the most and produces a loose granular aggregate known
to skiers as "Corn Snow". This transformation is accompanied by an increase in
density from less than 0.10 g/cm3 to 0.30 g/cm3 or higher. As the
processes of transformation continue, larger, more dense ice crystals are produced.
These transformation processes proceed smoothly until an ice density of
0.55 g/cm3 is reached. At this point the rate and mechanisms of transformation
abruptly change. It is at this point that glaciologists make the distinction between old
snow and firn. The density of 0.55 g/cm3 seems to be the maximum density
attainable through partial melting and compaction. Beyond this value other mechanisms such
as localized melting and refreezing, and re-crystallization take over until the average
glacial-ice density of 0.82 to 0.84 g/cm3 is attained.
Ice thus formed cannot be considered a glacier until it begins to move
down the slope or valley under its own weight. Internal resistance to flow and external
friction forces are seldom overcome until the ice reaches a depth of 18-20 m. Under
present circumstances the time needed to form this critical depth may take as little as 10
years in places such as Iceland or as long as 100 years in the Antarctica.
Under ideal conditions the average speed of glacial flow for a valley
glacier averages 30 to 60 cm/day. In very steep areas this flow rate may exceed 3 m/day.
Velocities up to 40 m/day have been documented for the large outlet glaciers of the
Greenland Ice Sheet. Short sudden bursts or surges have been noted on occasion for valley
glaciers. During a brief advance in 1937 the Black Rapids Glacier in Alaska attained
velocities of 75 m/day with an average of 35 m/day! During this particular surge the Black
Rapid Glacier advanced 4.8 km in six months. Surges such as the Black Rapid Glacier are
the exception rather than the rule.
Effects of Glaciers
Once identified, the footprints of past glaciers can be observed in
many areas today "outside" the current zone of glaciation. Probably the most
prominent glacial footprint is the U-shaped valley. Normal erosional processes produce the
standard V-shaped valley seen throughout the world. However, as the glacier begins to move
down the V-shaped valley the tremendous forces of the ice carve away the sides and floor
of the valley and transform the V-shape into a U-shape. The material carved away from the
valley sides and floor is pushed up along the sides and in front of the glacier to form
deposits known as moraines.
The formation of glacial-moraines can be visualized as being similar,
in process, to the drawing of your finger through wet sand. The sand ridges formed along
the sides of your finger would be termed LATERAL MORAINES and the sand ridge left at the
end of your drag line would be called the TERMINAL MORAINE. The third remaining major
moraine type is the medial moraine. The MEDIAL MORAINE is formed from the confluence of
two glaciers and the coalescing of their lateral moraines. The medial moraine can be
visualized as the middle ridge formed by bringing two fingers close together as you draw
them through the sand.
In addition to the above position classification, moraines can also be
classified according to their activity or their method of formation. For now we will be
content with position classification only.
The medial moraine is the most prominent form of active moraine in
valley glaciers, but is the least likely to form a permanent, stable feature. Few valley
glaciers have terminal moraines in contact with the ice at present. This is because
terminal moraines are formed from advancing glaciers and most of the glaciers today are
retreating. The lateral moraine is usually most obvious when it leaves the valley sides
and swings out into the plain of the valley where it forms an arcuate ridge as it merges
with the terminal moraine.
Moraines can vary in size and shape depending upon their age and the
activity of the glacier that deposited them. The terminal moraine of the Franz Joseph
glacier, an active glacier, in New Zealand, reaches the height of 430 m. Other high
terminal moraines can be found in the northern Italian Alps. Lateral moraines reaching
700-900 m height can be found in the southern French Alps.
Moraines are not always imposing land structures. In North Dakota there
are a series of washboard moraines that reach a height of 1.2 to 4.6 m, and are spaced 80
to 170 m apart. These washboard features occur at the end of the Mankato drift. Nearly
half of the former glaciated area of North Dakota is covered with washboard moraines.
Other prominent glacial footprints include kettle holes, erratics and
cirques. A kettle hole is formed when immense chunks of ice are left isolated under layers
of drift material as the glacier retreats. As the ice melts the overlying material slumps
down into the void leaving a kettle-like depression or hole. Often these holes fill with
water and turn into ponds or lakes. Kettle lakes are some of the most dominant features in
the northern states of Minnesota and Wisconsin.
The true glacial vagabond is the erratic. Erratics are rocks or
boulders that have been carried along by the glacier and then abandoned as the glacier
retreated. The sizes of erratics vary widely.
One of Europe's best known erratics is the Pierre a Bot or toadstone.
This erratic weighs about 3,000 tons and rests in the Jura Mountains of Switzerland, some
112 km from its source, Mount Blanc. Erratics can be found throughout Europe and North
America. The grand prize for largest erratic must, however, go to the vast
"Schollen" of Germany. The largest erratic there is 4 km long, 2 km wide, and
120 m in thickness!
Regardless of the size or location erratics give mute testimony to the
power and mobility of glaciers.
Other than the U-shaped valley, the glacial cirque is one of the most
easily recognized forms of glacial erosion. In its most classic form the cirque consists
of a rounded basin partially enclosed by steep cliffs and sometimes containing a small
lake or cirque glacier; the cliffs at the back of the basin (head-wall) may rise to
hundreds or even thousands of meters in height. The cirque is nature's amphitheater.
Wherever glaciation has occurred or is occurring cirques will be found.
It has been estimated that the Western Cwm (Welsh for cirque) on Mount Everest has a width
approaching 4 km and a head-wall height, if the ice were removed, of almost 2,800 m.
Conclusions
The causes of the ice ages are still the subject of speculation and
controversy. Most probably, several different factors are involved, and the most plausible
theories are those which are based on a combination of changes in land-mass altitude,
changes in the gas composition and particulate matter concentration of the
upper-atmosphere, and longer-term changes in the quality of solar emission. The complexity
of this interaction has been graphically summarized by Crowell and Frakes in Fig. 1.
Glaciers are the offspring of climate. They are totally dependent upon
the elements of climate for their birth and sustenance. The glacier's state of health, its
size, its activity, and its life span and history are controlled or influenced by
meteorological factors. The relationships between glaciers and controlling factors are
seldom simple or straightforward. Glaciers are competent and sensitive recorders of
climate because they are delicately tuned to the climatic environment. By learning to read
both the current and ancient glacial record we can learn how glaciers respond to changes
in climate. This information will then allow us to predict future glacial, responses to
climate and open a window to the possible climates of the past.
Table I
Present-Day Ice-Covered Areas (in km2)
Antarctica 12,588,000 Greenland 1,802,600 North-east Canada 153,000 Central Asian ranges 115,000 Spitsbergen group 58,000 Soviet Arctic islands 55,700 Alaska 51,500 South American ranges 26,500 West Canadian ranges 24,900 Iceland 12,200 Scandinavia 3,800 Alps 3,600 Caucasus 1,800 New Zealand 1,000 USA (excluding Alaska) 500 Others 100 TOTAL AREA 14,898,400
Further Reading
The following books and articles are intended to assist in further understanding the theme of the feature article "Glaciers: A Progeny of Earth's Climate."
EDITORIAL
THE ENIGMATIC GLACIER: IS THERE ANY HOPE?
Many creationists have difficulty addressing the time problems associated with past glaciation and the Ice Age. Some completely deny the existence of an Ice Age. Others accept one glaciation, but reject the multiple continental glaciation concept advocated by most glaciologists. Stratigraphy requires glaciation to be post-Flood. Biblical time constraints allow only one epoch of glaciation within post-Flood time, and require the ice buildup and subsequent melting to have occurred many times more rapid/y than could be allowed by conventional uniformitarian geology.
Tensions
Any effort to ease the tensions between the Biblical creationist
view and modern concepts of glaciology is hampered by the complexity of the subject matter
and the lack of a cogent "short time period" model. Progress, nevertheless, is
slowly being made in both of these areas.
Assistance in unraveling the complexities of glacial deposits has come
from engineering geology, petroleum geology, and sedimentology. Through the use of the
"depositional system" of the petroleum geologist, or the "land system"
of the engineering geologist, or the "basin analysis" of the sedimentologist,
the traditional "tills" and "type-sites" used to identify the
stratigraphic units in a glaciated area have been consolidated at many locations into a
single unit produced by a single event, rather than multiple units that accumulated from a
series of glacial epochs. In the book GLACIAL GEOLOGY: An Introduction for Engineers and
Earth Scientists, N. Eyles (ed.) makes the following statement:
"The term 'land system' is used because of the importance of landform recognition in interpreting subsurface sequences and expected variation in sediment type. It is a fact that in many glaciated areas, a PROFUSION OF FORMALLY IDENTIFIED SEDIMENTARY UNITS often reflects lateral and vertical variability WITH IN A SINGLE LAND-SYSTEM, the NUMBER of geologists who have worked in that area and OVERZEALOUS USE of formal stratigraphic nomenclature RATHER THAN A LONG HISTORY OF DEPOSITION." p.15 (emphasis supplied)
The significance of the landsystem approach for creationists is that many glacial deposits once attributed to multiple glaciation are now considered deposits from one dynamic glacier. Ancient ice sheets are now interpreted to have undergone many advances, retreats and surges similar to modern glaciers which show multiple surges and retreats.
Model Period
The most sagacious short time period model for the Ice Age, that I
am aware of, is that proposed by Michael J. Oard (U.S. National Weather Service, Great
Falls, Montana). In his paper "A RAPID POST-FLOOD ICE AGE" (Creation Research
Society Quarterly vol. 16, June, 1979), Oard proposes a scientifically competent Ice Age
mechanism which requires only approximately 500 years for the buildup of continental
glaciation. When buildup ceased, melting could have removed the glaciers within another
500 years or less.
Oard's mechanism is based on three key components. The first component
is the cooling of the mid- and high-latitude continents from volcanic dust trapped in the
upper atmosphere. The second component is a globally warm ocean immediately after the
Flood. This universal warmness could have been the consequences of (a) warmer than usual
waters coming from the breaking out of "the fountains of the deep" coupled with
(b) additional heating from large amounts of submarine volcanic activity and (c) an
initially warm antediluvian ocean. The final component is the moisture needed for the high
levels of snowfall necessary for the buildup of continental glaciers. This moisture was
provided by evaporation from the worldwide warm oceans. (Note the recent effects of El
Nino on the overall levels of precipitation.)
The significance of Oard's Ice Age model to creationists is that it
presents for the Ice Age a sound mechanism that is harmonious with the constraints of both
Scripture and science.
Hope?
Is there hope for this enigma? By all means, YES! There are many questions that are still unanswered but we need not despair. As more data come in, and as more individuals break away from extreme uniformitarian thought, the harmony between science and Scripture will continue to increase.
REFERENCES:
HOW-TO DEPARTMENT ...
Glacier A La Plank
No, I'm not talking about a frozen dessert! This simple classroom
demonstration assists in understanding the processes of moraine formation. If carried to
completion you may even end up with a Kettle lake.
Construction for this experiment is very simple. All that is needed is
an incline covered with 2-3 inches of sand and a block of ice from the local store. An
uncomplicated construction is shown in the figure below.
Several experiments can be performed by simply changing the angle of
inclination of the plane and/or the thickness of the sand. On a sheet of paper prepare a
table for recording the angle of inclination (height), rate of travel, thickness of sand,
and size and shape of moraines. You can then use this data to help your students use the
scientific methods of graphical interpretation.
You may use your own imagination to add variety to this experiment such
as placing "mountains" (big rocks) in the path of the glacier, etc. Let your
students plan some of the experiments and predict the results!
P.S. It might be best to place a large sheet of plastic on the floor in order to minimize the mess!
LIST OF MATERIALS
CALL FOR PAPERS
Do you have a restless pencil or a lonely sheet of paper? If so, why
not try your hand at putting the two together and writing a feature article for Geoscience
Reports, or sharing with others your experiences in the How-To Department?!
Feature articles should be 1,000 to1,200 words in length. The subject
matter should be on a science topic of general interest to teachers (K-12), with emphasis
on understanding God's created works. A list of further reading should be included with
the feature article, whenever possible.
The How-To Department should be singular in purpose and include concise
directions and illustrations. Topics should be readily adaptable for in-class construction
and/or demonstration.
All submissions are to be typewritten and double-spaced. All authors
should be identified by name, place of employment, grade level, and date, at the end of
the article.
If feature articles and how-to's are not your strong suit, why not try
an editorial?! Here would be your chance to share with others your concerns.
Submit all articles and inquiries to:
Editor, Geoscience Reports
Geoscience Research Institute
Loma Linda University
Loma Linda, CA 92350
NEWS NOTES:
The 1986 GRI Field Conference
The Geoscience Research Institute staff and twenty religion and science teachers from
our colleges and universities toured the Rocky Mountains and the Colorado Plateau for two
weeks during July. This traveling conference commenced at West Yellowstone, Montana, and
terminated in Zion National Park, Utah. Some areas of interest along the way were the
petrified forests of Yellowstone, Heart Mountain overthrust northwest of Yellowstone Park,
Dinosaur National Monument, and Bryce Canyon, Grand Canyon and Zion Canyon National Parks.
Lectures and discussions were held throughout the conference in meeting
rooms along the way and at strategic sites in the field. Some of the topics considered
were the origin of the petrified forests, radioactive dating methods, rates and limits of
evolutionary change among animals, the use of trace elements to establish temporal and
geographical parameters, paleocurrents, footprints in the paleontological record, flood
models, and the nature of inspiration, and the historicity of Genesis.
Major contributions on important topics were presented by attendees
from Andrews University, Loma Linda University, Southwestern Adventist College, S.D.A.
Theological Seminary and the White Estate. Other conference participants added much
through their daily morning worships and Sabbath services.
Field Conference for Secondary Educators
Geoscience Research Institute is planning a Field Conference for secondary
educators for July 13-23, 1987. All secondary educators concerned with issues in
creationism are invited to attend. The meetings will take place at Brianhead, Utah,
located in southwestern Utah at an elevation of over 9,000 feet. Lodging will be in
rented, furnished condominiums, each with a furnished kitchen. Academic credit should be
available.
The Field Conference will include lectures, discussions, and field
trips. Topics to be addressed include evidences of a world-wide flood, fossil forests,
radiocarbon dating, plate tectonics, changes in species, and the origin of life. Materials
and methods for teaching creationism will be discussed. Field trips will include Grand
Canyon, Bryce and Zion National Parks, Cedar Breaks National Monument, and a visit to a
stand of bristle-cone pines.
For further information, write to:
L. James Gibson
Geoscience Research Institute
Loma Linda University
Loma Linda, CA 92350
Geoscience Reports Winter 1986/87 No. 8
Editor .........................Clyde L. Webster
Associate Editor ..............Katherine Ching
Subscription requests, correspondence, and notices of change of address should be sent to: Geoscience Reports, Geoscience Research Institute, Loma Linda University, Loma Linda, CA 92350.
Geoscience Reports is a newsletter published by the Geoscience Research Institute to present current happenings at the Institute as well as articles of general interest which deal with creation/evolution issues for primary and secondary school teachers. The views expressed are those of the authors and not necessarily those of the Institute.
Staff of the Institute are: Ariel A. Roth - Director, Robert H. Brown, Katherine Ching, Harold G. Coffin, L. Jim Gibson, and Clyde L. Webster.