1. Patrick M. Colgan
A Brief Geologic
History of the Ravines
The Ravines
ravine (ra-vine’) A small valley, usually carved by running water; esp.
the narrow excavated valley of a mountain stream. Etymology: French, Patrick M.
“mountain torrent.” (p. 419, AGI Dictionary of Geological Terms, Bates Colgan is Associate
and Jackson, 1984).
Professor of Geology
The ravines are a natural laboratory for students and faculty at Grand at Grand Valley
Valley. Each semester, the Department of Geology introduces hundreds State University.
of students to the geosciences via the ravines, and each year geology stu-
dents conduct innovative research projects and ask new questions about
the ravines. Here, I summarize the geologic history of the ravines, how
humans have impacted the ravines, and what is still not known about the
natural history of the ravines.
The ravines formed by the episodic erosion of small streams over the
last 15,000 years. Water flowing off the upland, upon which Grand Valley
State University is built, drains eastward into the Grand River Valley via 11
the ravines. This broad, gently sloping, upland was formed during the Ice
Age by a glacier lobe depositing sediment in a large glacial lake. Follow-
ing this glaciation, the Grand River began eroding its valley through this
landscape. The ravines probably began forming at about the same time,
and by about 6,000 years ago they had grown to roughly their present
dimensions. During the last 6,000 years the ravines have grown during
brief episodes of erosion alternating with long periods of stability.
The Back Bone
The back bone of the ravines is a broad upland ridge, composed of a thick
pile of glacial and lake sediments into which the ravines are cut. This ridge
is nearly two miles wide and runs from north to south through eastern
Ottawa County for about ten miles. On the topographic map this ridge
looks like the back bone of a prehistoric animal, lying with its head to
the north where it is bordered by the Grand River and its long tail to the
south. The east-west trending interfluves that separate ravines are like
vertebrae that make up the back bone of the beast.
The ravines are eroded into sediments rather than bedrock, unlike
the mountain stream mentioned above. These sediments are generally
2. unconsolidated, not cemented together as bedrock is. The bedrock in this
part of Michigan is ancient sandstone and shale, buried by about 100
to 300 feet of glacial sediment left by the ice sheets that advanced into
Michigan over the last 2.5 million years. The most recent glaciation of this
Ice Age occurred in two phases between about 80,000 and 10,000 years
ago. This most recent phase of glaciation is known as the late Wisconsin
Glaciation. During this glaciation, massive outlet glaciers of the ice sheet
called “lobes” deposited glacial sediments over Michigan and as far south
as the Ohio River. The most important lobe of ice in this part of Michigan
was the Lake Michigan lobe. The Lake Michigan lobe reached its maxi-
mum extent about 21,000 years ago. At this time it extended south into
central Illinois. Another glacier lobe extend south through what is now
Saginaw Bay. Farther east, the Huron and Erie lobes extended through
those basins south into Indiana and Ohio. To the west, other lobes of ice
invaded Wisconsin, Minnesota, Iowa, and the Dakotas. Because these
glacier lobes eroded the land, they hollowed out great basins that would
eventually become our Great Lakes. By about 16,000 years ago, the Lake
Michigan lobe occupied the present lake basin and its margin was located
just east of the present campus.
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Gra
nd R
iver
end
GVSU Campus moraine
Figure 1. A shaded relief image of the topography in eastern Ottawa County
derived from digital elevation data (U.S. Geological Survey). Blue and green shades
are lowest elevations found near the Grand River, whereas brown and yellow tones
are the highest elevations found on the upland ridge upon which GVSU was built.
3. Patrick M. Colgan
As the Lake Michigan lobe continued to melt back into Michigan
by about 18,000 years ago, a series of lakes formed around the edge of
the ice. These lakes are called glacial lakes because they were bordered by
the retreating ice sheet. These glacial lakes contained icebergs and glacier
sediments were deposited in them as the ice retreated. One of the larg-
est of these glacial lakes is known as Glacial Lake Chicago, because the
present site of Chicago was where water from the lake drained down into
the Illinois and Mississippi Rivers. Sand, silt, and clay were deposited in
this lake. When the Lake Michigan lobe advanced, this silt and clay was
mixed with local gravel and exotic boulders carried by the ice down from
southern Canada. This mixture of boulders, gravel, sand, silt, and clay is
called “till.” Much of the University is built on this till. The till may be seen
in the foundations of most of the campus buildings and in a few gullies at
the heads of the ravines. The till is between ten and fifty feet thick over the
campus. Grand Valley students and faculty have mined the silt and clay
from the till and fashioned it into fired clay sculptures like those displayed
in Henry Hall Atrium (Formation, 1996, Daleene Menning).
A Cold, Dark Lake
The oldest sediments
exposed in the ravines
are clay, silt, and sand 13
layers that were deposited
in Glacial Lake Chicago.
Most of this silt and clay
probably settled out of
calm cold waters offshore
from where a river carried
sediment into the lake.
The river that delivered
this silt and clay may have
been an early glacial ver-
sion of the Grand River.
The silt and clay beds
probably took years or
decades to build up layers
only a few feet thick. The fine sands were probably deposited nearer to the Figure 2. Glacial till exposed
shore and the river mouth perhaps in a delta. We know this river flowed in the eroded stream bed in
from east to west just like the current Grand River because current ripples the ravine behind the Ravines
preserved in sand layers indicate flow to the west and northwest. Some Apartments. The boulder in
the upper center of the image
of the fine sands exposed in the ravines provide evidence for very rapid is probably granite. The scale
deposition, perhaps as much as a few feet in a matter of hours. The evidence is ten centimeters long.
for this is a feature called climbing ripples. Normal current ripples form in
4. fine sand that is being transported by a current across the bed of a river
or by waves along the shoreline. Climbing ripples form as layers of sand
rapidly build up on top of one another as the ripples migrate down cur-
rent. In this case, there is so much sand being deposited that the ripples
climb on top of one another.
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Figure 3. Upper
image is of ripple
cross laminations
preserved in sand
layers in a ravine
along the southern
boundary of GVSU
campus. These cross
laminations indicate
that flow was from
left to right. The lower
image shows climbing
ripples preserved in
another layer of sand
at the same site. Flow
direction is also from
left to right (both
images were taken by
Sarah Nagorsen, 2008).
5. Patrick M. Colgan
A Glacier Surge
As the Lake Michigan lobe wasted back into southern Canada it would
periodically surge forward as melt water built up under the glacier. This
occurs in many modern glaciers when they melt rapidly. Melt water on
the surface of the glacier flows down through cracks (crevasses) and holes
(called moulins) in the ice. When water reaches the glacier’s bed it can
cause the ice to float. This water greatly reduces the friction near the
bed of the glacier, and may cause the ice to surge forward. This has been
observed in modern glaciers in Iceland, Greenland, and Alaska, among
many other places.
During a surge, the edge of the ice may advance several miles in up to
a few years. It is likely that the Lake Michigan lobe experienced surges
similar to those observed in modern glaciers. As the edge of the ice
advanced into Glacial Lake Chicago it would bull-doze up sediment in
front of the ice and deposit till along under its margin. Because there are
numerous ridges of till called end moraines in West Michigan and around
all the Great Lakes, it is likely that the lobes of the ice sheet surged many
times between 18,000 and 13,000 years ago. The upland ridge upon which
Grand Valley sits is one of these end moraine ridges that probably formed
as ice surged into Glacial Lake Chicago.
Following a glacier surge the ice would waste back, and icebergs would 15
calve into the lake. Melt water would drain through the ice and discharge
from tunnels under the ice. Sediment would be deposited in the lake
around the margin of the ice, and glacial till would be deposited under
and in front of the ice.
The dense, boulder-rich glacial till that underlies most of the campus
and overlies the glacial lake sand and clay was the last sediment deposited
in the area. The till contains a plethora of different rock types some from
as far away as James Bay in Ontario and Labrador. Most of the larger
rocks in the till are local bedrock of sandstone, shale, and limestone. Still
there are many exotic boulders of granite, basalt, and gneiss. Many of these
large boulders can be seen used as landscape boulders and in retaining
walls all over campus.
The glacial till is very hard and resistant to erosion. It forms a hard
cap-rock over the softer glacial lake sediments below. As long as the till
is not eroded, the upland landscape is stable. Once erosion in the ravines
cuts through the till and reaches the soft lake sediments below, then ero-
sion proceeds very rapidly and deep ravines are the end product. This can
be seen in the ravine just to the east of the Ravine Apartments. Where
the till is still present the stream has not cut down as much as where the
till has been removed and erosion then proceeds rapidly.
6. A Barren Landscape Turns Green
After glacier ice disappeared from West Michigan, by about 15,000 years
ago, the landscape would have been a cold, windswept, and dusty place.
There was permafrost or permanently frozen ground at this time. Recently,
relict features indicating permafrost have been found on landscapes older
than 15,000 in Wisconsin and in eastern Michigan. It is likely that at this
time tundra vegetation would have been present (dwarf willow and birch,
and many different kinds of sedges). Animals such as mammoth and musk
ox were present in the Great Lakes region at this time. The lack of veg-
etation at least initially, would have led to dust and sand being blown up
out of the river valleys and deposited on top of the glacial sediments. This
wind blown silt is called loess. In areas to the south of Michigan along the
Missouri and Mississippi Rivers the loess piled up in layers up to 150 feet
thick. To the west of our campus on the flat lake bed of the former Glacial
Lake Chicago, sand dunes would have migrated across the barren surface.
Now most of those dunes are stable under woodland vegetation.
Between 10,000 and 13,000 years before present, the climate rapidly
warmed enough so that trees and grasses could begin to take a foothold in
Michigan. As forests and other vegetation spread, the landscape would have
supported ice age animals such as the Mastodon. Pollen records from bogs
16 and lakes in Michigan show the spread of spruce and pine between 13,000
and 10,000 years ago. By 10,000 years ago the climate was probably the
same or perhaps even a little warmer than today’s climate. Oak, maple, and
hickory began to invade Michigan by this time. Native American peoples
populated this landscape and took advantage of its many resources.
Birth of the Ravines
Most of the erosion that produced the ravines probably occurred very
early, just after the local deglaciation, starting approximately 15,000 years
ago. There are several lines of evidence for this. First, we know that the
Grand River had eroded its channel down to almost its current level by
about 9,000 years ago. River terraces above the present Grand River formed
before this time. The Grand River may have even eroded even deeper
than today because the lake into which it flowed was much lower than
the current Lake Michigan. By about 9,000 years ago there is evidence
that a very low lake level was reached in the Lake Michigan basin. The
earliest version of a non-glacial Lake Michigan is called Lake Chippewa.
Lake Chippewa was approximately 300 feet lower than the present Lake
Michigan (which is ~578 feet above sea level). Lake Chippewa was low
because of a warmer climate and the low elevation of the outlet to the
Great Lakes 9,000 years ago. The lake’s outlet was very low because the
great mass of the ice sheet had depressed the land, and at 9,000 years ago
it had not completely responded to the melting of the ice sheet yet. With
7. Patrick M. Colgan
time the eastern outlets of the Great Lakes would rebound and with this
land rising, the lakes would rise in level, just as the water level of a bath
tub will rise if you raise the drain. Even today, the outlet of Lake Superior
at Sault St. Marie is rebounding at a rate of about 20 cm of elevation per
century. This rise in the outlet causes the lake level of Lake Superior to
slowly rise over time. During the low Chippewa Lake level the rivers in
West Michigan responded to the low lake level by cutting deeply down
into their channels. The ravines would have been forced to cut down in
their channels as well.
Another piece of evidence for the depth of the ravines by 6,000 years
before present is in ancient wood found buried in the Little Mac Ravine
near it confluence with the Grand River. In the fall semester of 2006, geol-
ogy students drilled and collected two sediment cores near the mouth of
the Little Mac Ravine, approximately 10 feet deep. Near the bottom of one
core fossil wood of a log about a half a foot in diameter was penetrated by
the core. The wood was sent to a radiocarbon dating lab in Florida and the
returned age was 5,720 to 5,920 calendar years old (one sigma uncertainty,
Beta-223048). Since the valley had to be there before the sediment and
wood could fill the valley, this indicates that the ravines had eroded to a
depth greater than their present depth before approximately 6,000 years
before present.
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Sediment Fills the Ravines
Figure 4. Students in an environmental geology class taking a core in the Little Mac Ravine in the fall of 2007.
A buried log found in a core like this was radiocarbon dated as approximately 5,800 years old. This suggests
that the ravines were present and as deep as they are today before approximately 6,000 years ago. Photo by
Patrick M. Colgan.
8. The Little Mac Ravine is filled with at least 15 feet of sediment where it
meets with the Grand River based on the cores mentioned above. Most
of this sediment probably filled the valley as the Grand River responded
to the rise in Lake Chippewa Lake Levels after 9,000 years ago. By 6,000
years before present the lake reached a high lake level known as Lake
Nipissing. Lake Nipissing was between 20 and 30 feet higher than the
present lake level. Much of the Grand River Valley was probably flooded
at this time. Some of the ravines would have been flooded or at least have
been wetlands at this time. Clay, silt, and sand, along with logs and organic
material were deposited in the ravines at this time. As mentioned before,
fossil wood of approximately 5,800 years before present, suggests that
some of the sediment in the valley is at least that old.
Equilibrium
As the ravines became heavily wooded during the last 10,000 years, they
would have experienced long periods of stability (or equilibrium). As
long as vegetation held sediments in place erosion would be held at bay.
Events such as droughts and fires would have led to instability and brief
periods of erosion. During this time, soils formed on the upland and on
the ravine slopes below.
Settlement and Development
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With European settlement the land was cleared first for timber and then
for farming. This would have had an immediate destabilizing effect on the
ravines. It is likely that upland soils were washed down into the ravines and
rapid erosion occurred near the ravine heads. Aerial photographs taken in
1958, just before the GVSU campus was built show active erosion occurring
at the heads of the ravines at this time. Many of the ravine heads were
filed with field stones and garbage in an attempt to reduce erosion. The
ravines were used as a garbage dump at this time. The cleared fields and
orchards surrounding the ravine would have been highly susceptible to
erosion during spring and summer rainstorms especially in spring when
fields were bare and the ground was frozen. The very low infiltration rates of
the underlying glacial till would have made runoff and erosion a persistent
problem. In many ways the glacial till that underlies the campus is natu-
rally as impermeable as is today’s parking lots. Runoff during agricultural
use of the campus might have been as great as today’s runoff except that
most of the runoff then would have entered the ravines directly overland
and at the head of the ravines instead of as today in underground storm
water systems.
As the campus was established and grew in the 1960s and 1970s there
is strong evidence that erosion and sedimentation in the ravines increased
greatly. The 1958 aerial photos show that most of the ravine bottoms are
heavily wooded. Even aerial photos taken in the late 1970s show the ravine
9. Patrick M. Colgan
bottoms as heavily wooded. Today many of the ravine bottoms are filled
with dead trees and large open meadows. Many of the trees appear to have
died because sediment buried them and killed them as the soils became
waterlogged. In the small stream in Little Mac ravine tree stumps can be
seen buried by three to five feet of sediment. Logs buried in the sediment
are also found. This suggests that since the campus was built sediment
moved down off the upland into the ravines filling them in places with
three to five feet of sand, silt, and clay. This has had a dramatic effect on
the ecology of the ravines.
Today, uncontrolled erosion is occurring in many of the ravines, threat-
ening the stability and beauty of these natural features. Most of the threat
is because of runoff from parking areas and buildings. Storm water from
structures and parking lots is focused on the ravines so that today during
heavy rains the ravines truly are mountain torrents. Studies of the change
in the ravines during the past ten to fifty years have been carried out by
Geology Professors John Weber, Patricia Videtich and numerous past geol-
ogy students. Ongoing studies by Professor Peter Wampler and students
have begun to measure and quantify changes in storm water runoff. Prof.
Wampler estimates that since the campus was built that peak runoff in
the Little Mac Ravine has increased by more than 200 percent.
Some of the most dramatic erosion is occurring in the ravine behind
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the Ravine Apartments. Observations made by the author and others in
the Geology department indicate down cutting of the stream near its head
by as much as 10 to 15 feet. This has led to landslides along the sides of
the ravines and the toppling of trees some of which are more than seven
decades old. This clearly shows that the stability of the ravines has been
upset by recent human impacts. This could lead to the ravine in this area
becoming an unsightly mess of toppled and dying trees. Along the southern
campus boundary, runoff down an old access road and from an adjoining
farm property resulted in massive head ward erosion in a ravine tributary
between 2003 and 2007. This led to sedimentation in the ravine below
and its effects on the ecology of this ravine. This will probably lead to a
similar die off of trees in the ravine bottom similar to what happened in
Little Mac Ravine. Since the author arrived here in fall 2003, the erosion
only seems to be getting worse and with each record rainfall new and
irreparable damage to the ravines is occurring.
Professor Peter Wampler’s work with the storm water committee has
made a good start at developing solutions to the problem of ravine ero-
sion and sedimentation. His research group has recognized that a major
solution to the problem can only come from controlling and reducing the
amount of runoff directed to the ravines. Increasing infiltration in parking
areas, building rain gardens, and retention ponds can and hopefully will
improve the situation. If runoff is reduced, the ravines have a good chance
10. 20
Figure 5. Photograph of active erosion of a small tributary to a ravine near the southern boundary of
GVSU campus. Most of the erosion seen in the image occurred between 2003 and 2006 (Photo by Sarah
Nagorsen).
of reaching a new equilibrium with human land use changes. Other mea-
sures such as planting new trees in the valley bottoms, stabilizing eroding
slopes, and protecting eroding trails are other urgently needed steps that
need to be taken.
One change that could accelerate ravine erosion in the future are the
effects of global climate changes on precipitation in this region. Most
of us have heard of global warming and are familiar with its effects in
the polar regions and on glaciers, but one little known effect has been
a overall increase in rainfall in some areas as well as extended drought
in other regions. The Great Lakes region has seen only minimal tem-
perature changes during the 20th century due to climate change, but the
future could bring larger changes in rain and snow fall totals. Larger and
more frequent rainfall events have been observed in some regions of the
world due to human induced climate change. If we were to receive more
extreme or more frequent rainfall events because of climate change this
could make our ravines more susceptible to erosion and disequilibrium.
Warmer winters could also produce rainfall when in the past we would
11. Patrick M. Colgan
have received snow. Warmer and or wetter climates could lead to invasions
by new or non-native insect pests and or new tree species changing the
makeup of our woodlands in the ravines.
Alternative Futures
The future of the ravines like all stream valleys is of continued erosion and
eventually the denudation of the upland landscape. In tens of thousands of
years the ravines will certainly succeed in eroding most of the flat upland
topography upon which the campus is built. At this time the now smooth
upland will be reduced to a dissected complex of deep valleys and steep
ridges. Under natural conditions this would occur episodically and trees
and other vegetation would have time to adjust as erosion continued.
In the near term, most important to humans, the ravines face two
alternative futures. They could reach a new equilibrium with the chang-
ing climate and the newly imposed human impacts and become a stable
well-managed forest that can be used as a natural laboratory for all. This
future will require some careful, thoughtful management by all of the Uni-
versity community. Alternatively, the ravines could become an unsightly,
chaotic zone of unstable and eroding slopes with toppled, dying trees,
and a dense underbrush of non-native and invasive species. The choice
is up to the university community and those who manage the university
property. Hopefully, patient management by Grand Valley will choose the 21
former instead of the latter. We probably need to stop taking the ravines
for granted, assuming that they will always be a beautiful natural resource,
and start managing them with a purpose.
More Questions
The geological and environmental history of the ravines remains poorly
understood in many ways. Future student projects will hopefully shed light
on these questions. How deeply were the ravines eroded at the end of the
Ice Age? Cores taken from Little Mac Ravine have not penetrated the
deepest parts of the filled ravines. The deepest cores go down more than
15 feet and the bottom has not been reached. What is the oldest sediment
preserved in the ravines? So far the oldest radiocarbon age on fossil wood is
approximately 5,800 years old, but sediment twice that age could be found
in the ravines if our understanding of their formation is correct. How was
this sediment deposited? Was it deposited in a lake that backed up into
the Grand River Valley, or was it deposited in small streams eroding, and
then filling the ravines? Other questions pertain to the building of the
upland itself into which the ravines are cut. How big and how deep was
the lake into which glacial lake sediments were deposited? When and
exactly how were these sediments formed?
In summary, the ravines are a wonderful laboratory for our students,
where all of the long geological history of West Michigan is laid out for
12. those interested enough to inquire and learn about it. The ravines are
also a natural resource that currently needs some help and management
in order to retain their beauty and uniqueness.
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