Idea for 2014 field trip: Leave Fri aft; drive to Floodwoog bog, then to Itasca. Sat
morning drive to Perley then back to Itasca. Sunday morn: do drumlin then drive
home
GEOGRAPHY OF SOILS FIELD TRIP
Themes of Field Trip:
Soil Parent Materials derived from glaciers in Minnesota
Catena Concept
Forest-Prairie Transition in Soils
Practice in Soil Description Methods
Introduction to Great Soil Orders of the Taxonomy
Wear your seat belt at all times in the vehicles!
DAY ONE:
Leave UMD and drive to Floodwood (a one hour drive). On drive, notice flat (low
relief) landscape and abundance of bogs as we near Floodwood.
Floodwood: Gas up and have overview discussion in Rest Stop. Drive to peat bog on
Route 8.
First Soil Stop: PEAT BOG IN LAKE PLAIN OF GLACIAL LAKES
AITKIN AND UPHAM (Wear your rubber boots in the bog).
Glacial history in this region of MN is complex. Several advances from different
lobes) of the Laurentide Ice Sheet (Wadena, Rainy, Superior and Des Moines moved
through this region.
Each lobe in each advance deposited moraines. One of the advances of the Superior
Lobe left the Highland and the Mille Lacs moraines. The Highland moraine acted as a
dam and water was ponded to form Glacial Lakes Upham I and Aitkin I. Later, the St.
Louis sublobe (of the Des Moines Lobe) stagnated and Glacial Lakes Upham II and
AitkinII formed . These lakes covered an extensive area of northeastern Minnesota.
The lakes stood at several levels, and formed strandlines at each level. The
lake water also modified earlier deposits of till. On our drive to Floodwood and
Jacobson, we traverse Upham and Aitkin beaches and wave-washed tills from this
basin. Eventually, the lakes drained through St. Louis River around 9000 yrs. BP. You
will notice numerous peat deposits on the lake plain, where closed depressions have
filled with peat.
We will examine a core of peat from one of these closed depressions. The
peat deposits in the glacial lake basins here are extensive and many, such as the
Arlberg bog site in Floodwood, and have been mined to make peat fertilizer. The peat
soil in the Arlberg bog has 5-6 meters of peat above very fine sand of glacial lake
origin. Organic soils accumulate in these poorly drained old lake basins as a result of
anaerobic conditions. These soils have extremely low bulk densities (0.2 – 0.3
g/cm3) and high porosity (80%). The minerals in organic soils are tied up in organic
compounds and are not plant-available.
Important descriptive elements of organic soils are the botanical origin of the
organic material (sphagnum, grasses, sedges, cattails, wood and leaf litter) and the
extent of decomposition. A simple classification is:
Fibric (peat) <1/3 decomposed; >2/3 identifiable (Von Post H1 – H4)
Hemic (mucky peat or peaty muck) moderately decomposed (Von Post
H5 –H6)
Sapric (muck) 2/3 decomposed; <1/3 identifiable (Von Post H7-H10)
A more detailed classification is given in the Von Post method (below). We will
examine a core and use the Von Post method.
THE VON POST SCALE OF HUMIFICATION (source Ekono 1981)
Symbol
Description
H1
Completely undecomposed peat which, when squeezed, releases almost clear water. Plant remains
easily identifiable. No amorphous material present.
H2
Almost entirely undecomposed peat which, when squeezed, releases clear or yellowish water.
Plant remains still easily identifiable. No amorphous material present.
H3
Very slightly decomposed peat which, when squeezed, releases muddy brown water, but from
which no peat passes between the fingers. Plant remains still identifiable, and no amorphous
material present.
H4
Slightly decomposed peat which, when squeezed, releases very muddy dark water. No peat is
passed between the fingers but the plant remains are slightly pasty and have lost some of their
identifiable features.
H5
Moderately decomposed peat which, when squeezed, releases very “muddy” water with a very
small amount of amorphous granular peat escaping between the fingers. The structure of the plant
remains is quite indistinct although it is still possible to recognize certain features. The residue is
very pasty.
H6
Moderately highly decomposed peat with a very indistict plant structure. When squeezed, about
one-third of the peat escapes between the fingers. The residue is very pasty but shows the plant
structure more distinctly than before squeezing.
H7
Highly decomposed peat. Contains a lot of amorphous material with very faintly recognizable
plant structure. When squeezed, about one-half of the peat escapes between the fingers. The water,
if any is released, is very dark and almost pasty.
H8
Very highly decomposed peat with a large quantity of amorphous material and very indistinct
plant structure. When squeezed, about two-thirds of the peat escapes between the fingers. A small
quantity of pasty water may be released. The plant material remaining in the hand consists of
residues such as roots and fibres that resist decomposition.
H9
Practically fully decomposed peat in which there is hardly any recognizable plant structure. When
squeezed it is a fairly uniform paste.
H10
Completely decomposed peat with no discernible plant structure. When squeezed, all the wet peat
escapes between the fingers.
B1
Dry peat
B2
Low moisture content
B3
Moderate moisture content
B4
High moisture content
B5
Very high moisture content
Note: The moisture regime of each peat sample is estimated using the above scale of 1-5 and symbol “B”
(derived from Swedish blöthet = wetness).
NOTES and OBSERVATIONS ON THE BOG:
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After leaving the peat bog, we will drive to Jacobson and examine a cutbank of the
Mississippi River. We will continue west on 2 and turn left on 200 (west) to Jacobson.
Right after we turn left on 200, we cross a continental divide between Great Lakes
drainage and Mississippi drainage.
Second Soil Stop: GLACIAL LAKES AITKIN AND UPHAM
UNDERFLOW FAN AND LACUSTRINE DEPOSITS: JACOBSON
LANDING, MISSISSIPPI RIVER CUTBANK
This site on the Mississippi River exposes underflow fan deposits of the glacial lakes
and a sharp contact with the underlying gray lake clays. (If you look again at the
figure of the Glacial Lakes above, the unlabeled, smaller star marks the site we are
looking at).
In the cutbank of the river, you can see the lake sediments, with clear thin layers
called rhythmites. These are rhythmic accumulations of sediments that form
distinctive laminae. Annual cycles of deposition create rhythmites called varves in
glacial lake sediment. Each varve includes a coarser-grained “summer” layer,
produced by rapid ice melt in the warmer months and wave activity that keeps finer
sediments in suspension, and a finer grained “winter” layer, deposited from
suspension in quiet water while streams feeding the lake are frozen. Rhythmites can
also be caused by periodic changes in sediment source.
There are three things to take note of here: the rhythmites, the cross-bedding
produced by the underflow fan and the gleyed (grey) layers of lacustrine sediments
at the base of the hill.
Notes and Observations:
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THINGS TO NOTICE ABOUT THE LANDSCAPE AS WE DRIVE
TOWARDS HILL CITY AND BRAINERD:
As we drive west, follow our route on your color maps showing the landscapes
through which we are driving. We continue to drive through the expansive, flat lake
basin. Eventually we approach Hill City, presumably so-named because of the
relatively high relief in the Des Moines Lobe end moraine, the “Sugar Hills Moraine”,
in which Hill City lies. From Hill City, we head west to Remer and then south towards
Brainerd. Along the way, we travel through a jigsaw puzzle of end moraines of the
Rainy and Des Moines lobes and peat deposits in closed depressions.
Approaching Brainerd, we enter the pitted outwash plain, composed of outwash of
Des Moines and Rainy lobes. Notice the shallow, lake-filled depressions, sandy
sediments and droughty soils. Driving south from Brainerd, we follow the terraces of
the Mississippi. This outwash deposit is pitted with kettles and is composed of
meltwater sediment of both the Des Monies and Rainy lobes. Outwash spreads out
beyond the till in the form of a broad outwash plain, created by the merging of the
floodplains of many braided streams draining the ice. Long after the glacier melts,
these plains are criss-crossed by shallow abandoned channels and may also be pock-
marked by depressions or kettles formed by ice blocks which were rafted into the
outwash, then melted away.
Outwash may also exist in more narrow valleys which cut through the sheets of till,
in which case the resulting landform is referred to as a valley train. The Mississippi
Valley in this area contains glacial outwash in the form of a valley train. Outwash
plains and valley trains generally have different terrace levels developed along their
margins, reflecting formation of floodplains and downcutting of the rivers into those
floodplains as the volume of meltwater changes through time.
FROM BRAINERD TO STAPLES:
As we head west on 210 and 10 towards Staples, you will see on your color maps,
that we begin to leave the Rainy lobe deposits and enter the deposits of the Wadena
Lobe.
Third Soil Stop: WADENA DRUMLINS
(Ron and Sue Storbakken’s farm)
There are approximately 1200 drumlins in the Wadena drumlin field. The
drumlins are elongated hills of glacial till. They are quite evident on the topographic
map. The long axes of drumlins are oriented in the direction of ice movement, with
the less steep side of the drumlin pointing in the direction of ice movement. The
Wadena drumlins suggest that the ice was moving from the northeast to the
southwest. (See “Advance 4” in small figures). However, the source area for the the
Wadena Lobe is thought to be from the northwest, from what is now SE Manitoba.
Wadena lobe till is buff-colored, sandy, and calcareous. The common explanation has
been that another ice lobe deflected the Wadena lobe to the southwest, resulting in
the drumlins’ orientation. Recent research suggests that the Wadena lobe may have
come from the northeast and is really an early phase of the Rainy Lobe.
The drumlins in the field we are visiting are composed of loose material that
has been plastered into a very compact core. The bulk density of the core is very
high, 1.9 – 2.0 g/ml. (For comparison, loamy soils have a bulk density of 1.1 – 1.5;
concrete has a bulk density of 2.4). The core is encountered at approximately 4 – 5
feet below the surface (depth of frost). The core is so dense that it prohibits water
penetration. The depth of redoximorphic features tells where the water is
concentrated in the soil. We will examine a catena of soils on the slope of a drumlin.
Moving downslope, the redox features are closer to the surface, the sediment
becomes increasingly moist, and the texture changes because clay is moving
downslope. (In spring, there are springs in the side of the slope).
Working in four groups, collect cores from four topo positions on the side of
the drumlin. Core as deeply as you can and describe the core. Then we will place the
cores side by side to compare them. Use the 4 soil description sheets that you
printed, copy notes from the other groups, and answer the following questions in
your field book.
QUESTIONS TO ANSWER ABOUT DRUMLIN CATENA:
As a group, answer the following questions about the four soils:
1. What changes in A horizon thickness did you observe in the profiles? To what do
you attribute these changes?
2. What changes in color of the surface horizon did you observe in the profiles and
to what do you attribute these changes?
3. What changes in texture did you observe in the surface horizons of the profiles
and to what do you attribute these changes?
4. What changes in chroma values did you observe in the subsurface horizons of
the profiles and how do you explain these changes?
5. What redoximorphic features did you observe in the profiles? How can you
explain their presence or absence in the various landscape positions?
6. Did you observe any significant changes in soil pH in the profiles? Can you
hypothesize as to the reasons for those changes?
Put 4 soil description sheets here in your lab book
and leave room ( 2 pages) to answer the above
questions
ITASCA STATE PARK, UNIVERSITY OF MINNESOTA FIELD STATION
Itasca is the oldest park in Minnesota. It used to be called Omushkos, the Ojibwe
word for “elk”. The first white explorer called it Itasca as a combination of “veritas”
and “caput”, Latin for “true head”. We will look at some interesting things in the
park, including the headwaters of the Mississippi. From its headwaters here in the
park, the Mississippi travels 2,492 miles to the Gulf of Mexico, making it the third
longest river system in the world.
DAY TWO:
FOREST-PRAIRIE TRANSITION:
There are many theories attempting to explain the abrupt transition in Minnesota
from forest to prairie. These theories range from climate change to fire patterns to
changes in topography. Prairie and forest vegetation have existed in Minnesota since
the Pleistocene glaciation. The prairie/forest transition was very dynamic and everchanging before European settlement. The changing border was dictated by the
frequency and severity of fires and weather patterns. Several different kinds of
communities existed along this transition zone, including brush prairie and savanna.
Before settlement, the “Big Woods”, existing south and west of the Twin Cities,
covered over 2 million acres in Minnesota. Currently the remaining acreage of the Big
Woods is mainly comprised of the late-successional species of maple and basswood
referred to as maple-basswood forest. The first trees to invade the prairies were oak,
aspen and willow, followed later by elm.
Fires started by lightning and by American Indians were originally the primary
obstacles to forest invasion into the prairie. Frequent fires spread easily over the
prairie, killing most invading trees and shrubs, but were extinguished when they
reached the moister forest regions. The prairie grasses would quickly regenerate
after the burns but the large burr oaks were resistant to fire, and the willow and
aspen regenerated quickly after burns at the transition. A later shift in climate to
cooler, wetter conditions in the Big Woods likely ushered in the shift from oak and
aspen to elm.
Settlement of the transition area brought with it extensive fire control to protect
buildings, crops, livestock, and the surrounding woodlands. Constructed railroads
and highways served as fire breaks. This fire suppression has and continues to lead
to the invasion of the forest into the remaining native prairie lands. Prescribed
burning is now used to manage the remaining native prairie.
Fourth Soil Stop: BAD MEDICINE LAKE ESKER: FOREST SOIL
(ALFISOL) IN WADENA LOBE DEPOSIT
(As we drive to the first stop today, we will be crossing another continental divide
between Hudson Bay drainage and Mississippi drainage).
We will look at two forest soils, one in Wadena lobe deposits and the second one in
Des Moines Lobe till. The first deposit is on an esker. An esker is a long, winding,
narrow ridge made up of stratified sand and gravel, deposited by a subglacial
meltwater stream. This esker formed at the margin of the Wadena lobe and is
composed of coarse gravelly material.
This soil is an Alfisol. We will compare the forest soils to the prairie and the forestprairie transition soil. Notice all of the characteristics of this soil that make it a forest
soil.
Fifth Soil Stop: FOREST SOIL (ALFISOL) IN DES MOINES LOBE
DEPOSIT
The next three sites show changes that occur traversing the transition zone between
prairie and forest. All 3 sites occur in the same parent material, Des Moines lobe till.
This site is still in the Des Moines lobe till, which is finer-textured and more
carboniferous than the Wadena lobe till. This area is in a stagnation moraine, which
formed in a body of ice, cut off from the main glacier, which melted in place, leaving
the irregular topographic moraine surface. This alfisol formed in a forest. Note all the
features of this soil that make it a forest soil.
Sixth Soil Stop: FOREST/PRAIRIE TRANSITIONAL SOIL
We are now in an area that has experienced both deciduous forest and prairie
influences over the past 10,000 years. The soils here have characteristics of both
Alfisols and Mollisols: a thick dark A horizon, a thin E horizon, an argillic horizon, and
moderate depth to carbonates. This soil is called a “Mollic Hapludalf”.
Seventh Soil Stop: PRAIRIE SOIL
Prairie vegetation dominates landscapes to the west on Des Moines lobe ground
moraine, which has relatively low relief. Here the landscape is made up of beach
ridges, inter-ridge complexes and lacustrine sediments.
The topographically higher landscapes are dominated by forests and are composed of
Itasca End Moraine (from the Wadena Lobe) and the Big Stone Stagnation Moraine
(from the Des Moines Lobe).
The prairie soil that we will look at is a Mollisol, with the typical deep, dark, mollic
epipedon characteristic of grassland soils. Working in groups, we will describe a
prairie soil here.
PASTE A SOIL PROFILE DESCRIPTION SHEET HERE.
LAKE AGASSIZ : BEACH RIDGE AND LACUSTRINE SEDIMENTS
Glacial Lake Agassiz was formed as the retreating ice towards the end of the
Wisconsin glaciation blocked the northward flowing drainage towards Hudson Bay.
During this time, the lake had multiple stages and multiple outlets. The primary
outlet was over the Big Stone Moraine (in the vicinity of Brown’s Valley, MN), which
created Glacial River Warren that formed the current channel of the Minnesota River.
The various lake stages left a series of continuous beach ridges along the perimeter
of the lake. The beach ridges are composed of sand and gravel and often show
cross-bedded strata. The beach ridges are often mined for sand and gravel, being
the only local sources. The inter-beach areas trap water and are quite wet.
The lake sediments themselves form Vertisols in deep deposits of silty clay. The lake
plain itself is extremely flat, with relief in some places only one inch per mile.
Ditching in this region can be seen on the topo maps. It removes water from the
surface, and has led to productive agriculture, especially of sugar beets and small
grains. But the ditching has increased peak flows to the Red River and may be partly
responsible for severe flooding in recent years.
Eighth Soil Stop: BEACH RIDGE
The Beach Ridge we are going to see is in the Twin Valley Prairie Scientific
and Natural Area. This prairie remnant is 339 acres and is dominated by big
bluestem and prairie cordgrass. Sandhill cranes stop here on their migration and
prairie chickens boom here during mating season.
Ninth Soil Stop: LAKE CLAY
We will drive to a cutbank of the Red River and look at the soils developed on
lacustrine sediments of glacial Lake Agassiz. Locally, these clayey soils are called
“gumbo soils”.