Original Proposal | Final Exhibit Components

Soil is vital to mankind's existence: it supports the growth of plants upon which all life on earth is based; soil filters the water which we drink; soil and its underlying rocks support the structures we build. Despite the obvious importance of soil, most of the soil scientists we contacted believe that the general public knows little about soil or its physical properties. Typical was the comment of Dr. Ray Tucker, Chief of the Soil Lab at the North Carolina Department of Agriculture: "As a general rule, all of the public is woefully ignorant of the chemical, physical, and biological properties of soil and the many benefits we derive from these properties." A survey of relevant organizations ­ the National Wildlife Federation, the Soil and Water Conversation Society of America, the Natural Resources Conservation Service ­ revealed no systematic surveys or other information on the general public's perceptions about soil.

The lack of knowledge of the public regarding soil is mirrored by a dearth of museum exhibitions which deal with the physical properties of soil. Most of the exhibitions under development are slanted toward the organisms which live in soil, rather than the physical properties of soil, and few of the exhibitions travel.

REVIEW OF RELATED EXHIBITIONS AND APPROACH

"Dirt" will focus to a large extent on the physical properties of dirt, not just on what lives there. Soil is important to people for a number of reasons: we build structures on it; we grow things in it; it purifies and recharges our water; and its movements via ice, water and wind change the topography of our earth. "Dirt" will look primarily at how the physical properties of soil influence each of these functions in ways not present in other exhibitions on soil.

In our research, we identified several related exhibitions. A 10,000 square-foot installation at the Field Museum in Chicago emphasizes life underground in prairie regions. The Cincinnati Museum of Natural History has an exhibition on the sensory apparatus of animals underground. The Boston Children's Museum, is currently developing a permanent exhibition, "Life Under a Rock," again emphasizing life underground or at least out of direct view. In part as a result of this research, we centered our exhibition on the physical properties of soil.

"Dirt" is built around conceptual areas selected by our advisory committee of science/education professionals and by front end interviews with 75 children (PreK ­ 5). Despite their general lack of knowledge about soil, the children interviewed were enthusiastic about "dirt". Topics most often mentioned by this elementary-aged audience were "making mud pies", "building dams", "finding worms", and "playing with water and dirt." Our exhibition will use these hooks to encourage interest in basic concepts of soil science.

EDUCATIONAL GOALS

After participating in the exhibition, families will be more aware that:

• there are different kinds of soil, each with unique properties;
  
• soil performs unique functions in the environment, such as purifying water;
  
• soil, like water, is a substance that should be conserved; and
  
• soil supports our structures and provides habitat for a diversity of living things.

THE EXHIBITION

Families will enter "Dirt" through a giant "mole hole." Once "underground" families will find themselves in an environment structured to look as if they were underground, with simulated roots hanging from the ceiling, subdued lighting, earth-color exhibit modules, and wall graphics such as electron photomicrographs of large dirt particles, and thin sections of soil. Families then proceed to the five exhibit sub-sections, each focusing on a specific theme.

I. What is soil?

The components in this section introduce the fundamental constituents of soil, a very diverse material. A typical topsoil may contain (by volume) 45% minerals (soil particles transported or derived from weathered rock), 25% air, 25% water, and 5% organic material (e.g. dead plant and animal material).

Dirt Particles: Soil particles provide soil its texture and contribute to many of its properties. Here, families will "make" three types of soil components (sand, clay, silt) while learning about the different shapes of soil particles, their relative sizes, and the effect this has on each soil's characteristics. By stacking 5 cm - 8 cm, differently shaped, colored plastic soil particles into clear Plexiglas containers, participants will find out that the particles stack differently, resulting in different pore sizes of these three soil components. The different shapes ­ flat "platy" for clay, "angular blocks" for sand, and "spheroid" for silt ­ will be different colors (e.g. red for sand, blue for silt) to allow for resorting by the families. The exhibit module is can be reset using dump handles. An accompanying model will show the true scale soil particles (e.g., clay particles are 1 mm; sand 300 mm). Scanning electronic microphotographs will show families what the "real thing" looks like.

Dirt Lab: Families will test basic properties of soil in a four-sided lab area with a protective floor mat, which will encourage families and other groups to work together. Families can:

• Test particle size by using sieves of different meshes.
  
• Use a Munsell Color chart to identify soil colors. Color is an important source of information about soils (e.g. a red soil indicates the presence of iron oxide; blue or gray soil indicates the soil originated in a marsh). Color is also useful to determine the organic content of each soil (e.g., black prairie soils have about 7 - 8% organic materials compared to 1% - 2% in yellow timber soils).
  
• Test the angle of repose of different types of soil particles (i.e., slope of a stable pile of soil particles until collapse) by turning over hour-glass containers with different types of soil. This angle will be related to the soil's ability to support weight.
  
• By flipping over clear Plexiglas containers containing water and soil materials, families will find out that larger particles (pea gravel) settle fastest. Accompanying graphics will relate settling rate to how settling occurs in a stream or pond and the effect of soil runoff (and its attendant clouding of the water) on aquatic ecosystems.

Dirt Around the USA: By turning flip panels with different soil samples, families can identify the kinds of soils that come from different areas of the U.S. The soil types can range from the sandy soils from the southwestern U.S. to the red clay from southeastern U.S. to the rich black organic bog soils from glacial kettle holes (New England), and green sand marl (from New Jersey), Wentz microscope to examine thin sections of various soil samples, revealing unexpected beauty and identifying elements of soils with biological origins, such as Diatomaceous soil from Arkansas and phosphate soils containing fossils.

II. How is soil made?

Soil is formed during a complex process called the "rock cycle" which begins with bedrock which is weathered by temperature, climate, and biological action through a series of stages to end up as mature soil. Mature soil is then further eroded and redeposited on land or in the ocean where chemical and geological transform it into rock once again.

Rock Cycle will feature a video disk program illustrating the basic stages of the rock cycle and the stages of soil formation. By using random access techniques, families will discover how soil comes from weathered rocks, decaying plants, and animals and that soil scientists have identified over 8,000 types of soil in the U.S. alone.

Erosion will be explored with a stream table that erodes landforms made of sand and redeposits the particles downstream according to particle size. By manipulation of the stream and special fiberglass "landforms", families can create fast-rushing streams which "erode" the sand, and meandering streams which re-deposit the sand, much like an actual river. Another experiment which families can try is modeling of the Johnstown flood. (See "Dirt Disasters" next section.) By building the dam and storing water behind it, families will create the conditions for the "flood." By sprinkling water on the dam, they can saturate it and cause it to fail catastrophically. The stream table will be built by Science North, Sudbury, Canada, which has designed, prototyped, and fabricated successful stream tables for their exhibition floor.

III. What is soil good for?

Soil is vital to mankind's existence. It is utilized for things as diverse as supporting buildings and purifying water to providing nutrients necessary for growing plants and the raw material for works of art.

In Supporting Soil, families will find out what kinds of soil provide buildings with a firm foundation. They will load large, angular "blocks" of soil particles into Plexiglas cubes. One "block" will represent a sand of a single particle size (8 cm), while the other is a well-graded sand with a range of particle sizes (represented by blocks of 2 cm - 8 cm). After leveling the surfaces, families will put a model building on each pile and lower the sides of the cube. Each pile will then settle, revealing that the well graded sand forms provide a much more stable foundation for the building. Depending upon the results of exhibit prototyping, we may also incorporate a shake table within this module, allowing families to tell the stability of the two piles of sand particles under more extreme conditions.

In Liquid Soil, families find a clear Plexiglas container 3/4 full with "boiling" fine sand; the "boiling" is caused by circulating water up through sand with a pump. By turning off the pump, families will let the sand settle for a few seconds to a solid configuration and then place a model building on top of the supposedly-solid column. However, by shaking the container, the sand will "liquefy," allowing the building to sink into the sand. Graphics relate this to the Loma Prieta, CA earthquake of 1989 and to common beliefs concerning "quicksand."

Nature's filter focuses on the role of soil in purifying water. By pumping water with suspended fine sand through a gravel/sand column and letting clear water seep out, families will discover how soil acts as a natural filter in streams, septic tanks, or drainage fields. Replacement sand/gravel columns will be stored in the module's base to replace the primary column when it gets clogged. Graphics will show how this technique is used in the real world, such as when the soil of a septic tank drain field becomes clogged at the interface of the drain field and soil surface. The sand/gravel column will be backflushed when clogged.

The Dirt Farm will illustrate how soil supports plant growth. A thin aquarium, like that used for an ant farm, will be filled with soil and bean plants so that families can see the roots of the plants. Accompanying graphics will detail how the physical characteristics of soil ­ pore size, organic content, air and water content ­ provide an environment in which plants can grow.

Dirty Art: Parents and children alike will get dirty and creative at the same time by making pottery out of self drying potter's clay at 4-sided table top which will encourage families to work together on their creations. Accompanying graphics will display pottery from different civilizations and describe the physical characteristics (e.g. high water content and the flat shape of the clay particles) which allow clay particles to slide over one another, giving clay its plasticity and making it a suitable material for making pottery. Smocks and hand washing bins will be provided.

The Folklore of Dirt. Sayings like "You have to eat a peck of dirt before you grow up" and "Cleanliness is next to Godliness" are indicative of the wide range of behaviors and traditions associated with dirt. This graphic module will trace the roots of some interesting sayings and behaviors and explore related topics such as the basis for the western emphasis on cleanliness.

B>IV. How can we save soil?

Recent studies indicate that the U.S. is losing 5.8 billion metric tons of soil each year due to erosion. The eroding soil is washed into lakes and rivers and blown into our air where it pollutes our environment. This series of exhibits will show what each of us can do to reduce soil loss.

Save That Dirt: A Computer Touch Screen game will quiz families about simple soil conservation techniques and related facts. Concepts will include the importance of replanting eroded areas, not dumping wastes such as household chemicals or used motor oil onto the ground, using city sewer system instead of septic tanks when possible, and the installing soil-trapping fences around construction sites and on beaches to prevent dune erosion. An interesting fact that will be included in the game: it can take natural processes 500 years to form one inch of top soil, but poor farming and landscaping practices can allow this amount of soil to erode in less than a single day!

Dirt Disasters: "The History of Dirt Disasters" will feature a video disk showing instances when soil conservation practices were not followed. "Dirt disasters" such as the Dust Bowl, the destruction of the ocean reefs by silt runoff, "slash and burn" agriculture in Central America, and strip mining, will be accessible with accompanying information.

V. What lives in soil?

Soil is a diverse habitat which supports many types of life. The animals and plants which inhabit the dirt often change and enrich the soil by their activities.

What Lives Underground? This diorama will feature a representative soil profile, beginning at the surface with humus and moving down to bedrock. Families will find familiar organisms such as moles, plant roots, and worms, as well as less familiar organisms like slugs, isopods, and millipedes. Using touch plates, families will find recorded messages describing the specimens, and when relevant, the actual sounds made by the animals. A large magnifying glass mounted on slide rails will allow closer examination of the specimens, and a simulated microscope will allow families to see magnified views of the microscopic inhabitants of the soil (e.g. nematodes, bacteria, fungi). The recorded messages will relate interesting facts about soil's inhabitants. For example, earthworms actually "eat dirt", digesting the organic matter to make the surface soil richer. Thirty earthworms can digest more than one ton of soil in a year!

Soil Zoo: Using dissecting and video microscopes, families will see isopods, millipedes, and springtails they gather from the rich compost. (Liberty Science Center has perfected the use of a compost pile in a museum setting and we will build upon their experience in our exhibit.) After examining the sample soil, families can also collect and examine soil from around their homes/schools. Graphics will detail the roles which some of these common animals play in the development of soil. Millipedes, for instance, feed on plant litter helping to further the breakdown of these materials into soil. Slugs feed on living plant materials and leave droppings which enrich the soil's organic content.