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Hydrology Vegetation History Zone: 5, 4, 3, 2, 1

Volo Bog State Natural Area, Ingleside, Illinois
Volo Bog is a wonderful example of a kettle moraine. We will learn what formed the kettle, the plant life that can survive in this area, and the surface as well as ground water hydrology.

Volo Bog was a kettle lake formed by a large chunk of glacial ice (see diagram labeled A-H) and is filling in with vegetation in a concentric fashion (See Figure, McComas, 1972).

A. Glacier advances over proglacial sands and gravel, depositing sand and gravel, depositing thin till (Haeger) and sand and gravel with incorporated ice blocks.
B. Ice block near Algonquin forms dams and creates Lake Wauconda; ice blocks become islands in lake. Clay is deposited in lake over sand and gravel.
C. Ice block dam breaks, and Lake Wauconda drains via the Fox River.
D. Wadsworth glacier advances from east and deposits sand and gravel over clay.
E. Area drains. Deposition of loess on sand and gravel. Colluviation begins.
F. Area has drained to maximum water table decline. Marl forms in shallow lakes and organic debris accumulates. Upland depressions partly fill with colluvium.
G. Water table and lake levels rise. Reed and sedge growth on periphery of the lakes is periodically drowned by rising water. Organic debris accumulates on top of the marl and at sides of lakes.
H. Water table rises to within 5 feet of present elevation. Reed and sedge peat forms along lakeshores. Bog fills with organic debris.

Regionally Volo Bog is located in the Upper Fox watershed (See Figure, EPA website), however locally it has its own. The bog and surrounding lakes are poorly drained because locally the gradient in elevation is low. Originally the surface water in Volo Bog drained to the northwest into Brandenburg Lake until settlers wanted to drain the area for farming. Through their attempt they changed the flow of the surface water south to Sullivan Lake through ditches and a culvert then northwest through Lilly lake drain to Pistakee Bay (Figure 18 Drainage of Volo Bog, McComas, 1972). The bog primarily gets its surface water from precipitation but also gets it from run-off thus making it a fen. The surrounding surface is very permeable and the organic matter has a high retentive capacity. Through out the year the pond in the center of the bog as well as pools on the sphagnum mat and surrounding marshland retain water. The high hydraulic conductivity of the organic matter permits the water to flow freely between the pools. The surface water seen here is also the water table or the contact between the saturated and unsaturated soil. Due to the high permeability and porosity of the mostly sand and gravel subsurface, groundwater flows relatively fast through the saturated area (See Figure, EPA website). The water enters the subsurface in the recharge areas of the basin moves laterally and is discharged to the surface in the ponds, marshes, and streams which is determined by gravity and pressure gradients within the saturated zone. Along areas of recharge the gradient is downward from the water table and in the discharge area it is upward to the water table and the difference between the two produces the lateral movement along the water table.

Originally Volo Bog was a deep 50-acre lake with poor drainage and steep banks. With the aid of preserved pollen in the bog, scientists have determined that the lake began filling in with vegetation approximately 6,000 years ago. The vegetation began with sphagnum moss that formed around the outside edges in and amongst the cattails and sedges. As the plants died and decomposed, the peat thickened providing supporting materials for other plant life. Volo Bog contains the thickest known deposit of peat in northeastern Illinois where 34.56 feet of peat have been measured. In northern Europe, peat is harvested, drained of its water, and cut into bricks. The Europeans use these bricks for heating and generating electricity. Due to the sphagnum moss and the fact that there was no drainage outlet, the water became highly acidic. Only certain species of plants can survive here because of the high acidity and low oxygen content. In 1977, Dr. James King studied preserved pollen grains. Ragweed pollen was discovered in the top .8 feet of the peat. From this observation, it is evident that this plant began its growth in Illinois about the time that European descendents came here. Ragweed, because it was not originally here in the United States, would be classified as an exotic species. Near the bottom of Volo Bog's basin, Dr. King found pine and fir pollen. Using carbon dating, it was determined that these evergreens grew in the area between 10,000 and 11,000 years ago.

Volo Bog was a lake formed by glacier meltwater as the glaciers retreated. As seeds and spores were carried with the wind, a plant community was produced. Plants died and fell to the bottom, but due to the high acidity and low oxygen content, decomposition was slow. The layers that accumulated are referred to as peat. Because the lake is filling in very slowly, there are five easily distinguishable habitat zones. Starting in the center with the open water surrounded by sphagnum moss, the zones are (Figure 21 Zones of Volo Bog, McComas, 1972):
Zone 1 - Herb Mat
Zone 2 - Low trees and shrubs
Zone 3- Tamarack Trees
Zone 4 - Tall shrubs
Zone 5 - Marshland
Based on recent changes in scientific terminology, Volo Bog is not really a bog, it is a fen. A bog receives water from precipitation only, and since Volo Bog receives its water from ground water and runoff, it is a fen.

Your journey begins in Zone 5. This type of environment forms in poorly drained areas that are saturated or covered with water during the growing season. The growing season is typically the spring and early summer months. The soil in this zone is peat from the surface all the way to the bottom. The water depth varies depending on the time of year. In the past, the depth has been measured as deep as 1.6 feet. During drier times, it is possible that no water would be present in this zone at the surface. Plant species than can be found in this zone include cattails. In late spring, the flower develops and turns brown during the summer months. In the fall, the seeds ripen and burst open to be dispersed by the wind.

Continuing on, the plant community changes to tall shrubs, this is Zone 4. This area contains poison sumac (See Photo). In the spring and summer months, it is characterized by its green compound leaves and gray branches. In the fall, this shrub is noticeable by its reddish-brown leaves. After the leaves have dropped off, it retains its off-white berries. Another plant that is easily identified in this zone is Winterberry Holly (See Photo). It has bright red berries that remain on the plant throughout the winter. Buckthorn, the tall shrubs with the dark gray bark and white markings are also encountered in this zone. This plant is exotic to Illinois. It was brought from Europe and planted here as an ornamental shrub. Birds enjoy eating the dark blue berries and by doing so, disperse the seeds of the Buckthorn to different communities across the world. The downside to this shrub is that the seedlings grow quickly and block out light for growth of native species in the area. If you look down towards the boardwalk you will notice the leaves of the Sensitive Fern (See Photo). During the spring and summer months it is a green multi-leaved plant. When the temperature at night begins to get cooler, the leaves turn brown and hence the plant was named Sensitive Fern. The tall trees growing out of the dense shrubs are Trembling Aspen. This Aspen gets the name "trembling" because the leaf stalks are very long and flat which allow the whitish leaves to quake with the slightest breeze. In this zone, it is also possible to see some of Illinois's native species: Milkweed and Sunflower. The dominant plant in this zone as well as throughout any bog is sphagnum moss. When cattails, reeds and sedges began filling in the original glacier lake, sphagnum moss (See Photo) filled in the open spaces between the plants. Sphagnum moss forms a floating mat on top of the water. The sphagnum moss floats because of gas filled cells that allow is buoyancy. The water containing the moss is always acidic because the moss absorbs bases and releases acids. When sphagnum moss dies, it decomposes very slowly and incompletely because of the acids and lack of oxygen which keep bacteria from growing. The sphagnum moss insulates the water underneath it. Because of this, the layers under the moss stay cool all year long. In late fall, it takes longer for the water and peat to freeze and in the spring, it takes longer for these layers to thaw.

The trees that are growing out of the sphagnum moss are Tamarack trees (See Photo) in the Third Zone. Tamarack trees, also referred to as American larch, are shallow rooted deciduous conifers. Although it is a pine tree, it is deciduous - it looses all its needles each fall. By doing this, the Tamarack is able to conserve water during the winter because there is less surface area exposed to the winds. Some of the Tamaracks here at Volo Bog reach heights of 50 feet. In the spring and summer they are green needled trees but in the fall, their leaves turn golden and fall into the bog. The needles that fall release tannic acid in to the peatland. This release of tannic acid also maintains the high acidity of the bog.

The next zone, the Low Tree and Shrub Zone, is characterized by young Tamarack trees. The zone may be hard to decipher from the Tamarack Zone but it is also marked with a plant called Leatheleaf. In the spring, Leatherleaf (See Photo) produces white bell shaped flowers. To survive in an environment where water temperature is cool and the water is nutrient poor, Leatherleaf has adapted to these conditions. Leatherleaf has waxy leaves which enable it to retain water. The leaves turn reddish-brown in fall and remain on the shrub throughout the winter. When spring comes, the Leatherleaf begins to turn green. Leatherleaf in Volo Bog is the first plant to bloom, usually around mid-April. The pitcher plant is also found in Zone 4. Remember, the pitcher plant is a green plant which supplements its' diet by nutrients obtained from "digesting" insects that get trapped in its cilia.

The last zone encountered before the open water is called the Herb Mat. The plants that are able to grow here are on a thin mat too delicate to support the heavier shrubs or trees. Underneath this mat is about 50 feet of water and mud. Duckweed (See Photo) is a common species here in the Herb Mat. Duckweed has small green leaves that are in clusters. In this zone, we also encounter more sphagnum moss.

The center pond of the bog was deeper but has been continually filling in with organic material. This decaying material at the bottom as well as living plants on the surface contribute to the bogs acidity (See Figure). Alkaline water, which is in the sand and gravel subsurface, moves upward through the organic material and becomes acidic. This groundwater flowing through the organic material created the initial acidity that is optimum for sphagnum growth, which in turn adds to the acidity of the bog. Large amounts of alkaline surface water into the bog could adversely affect the supporting plant life so to prevent this the water level within the bog is controlled.
Human activity is also responsible for the bog not being completely covered by the sphagnum mat or drying up completely. The McHenry dam located across from Moraine Hills on the Fox River keeps the regional water levels high including Volo Bog preventing further drainage. With continued development within the Upper Fox watershed, near Volo Bog, of impervious urban structures such as: roads, houses, and parking lots surface run-off would increase into the bog. The introduction of greater amounts of alkaline water would upset the pH balance and be detrimental to the bog's flora.

Directions to Volo Bog Extensions for Teachers