Most of Florida, including Alachua County, was formed by sedimentary processes that have occurred in relatively recent geologic time. Alachua County lies in the North-central portion of the Florida peninsula and is part of the Central Highlands or Central Florida Ridge of the Atlantic Coastal Plain. Its 965 square miles are comprised of low, flat limestone plain in the west bounded by a west-facing escarpment (steep slope) and a flat upland plateau in the east. Elevations in the County range from approximately 25 feet above sea level near the Santa Fe River to over 195 feet northwest of Gainesville.
The primary land use in Alachua County, in terms of acreage, is agricultural, including cropland, specialty crops, and forestry. With urban development encroaching on farmland, it is important to assess the qualities of that land for agricultural use. In terms of the natural characteristics of soils that make it more or less suitable for various uses, most exhibit a wide range throughout the County.
Many soils have characteristics that limit their ability to be developed in their natural state. While poor drainage is perhaps the major limitation, others include wetness (amount of water in the soil at various times of year), effective depth (to water and plant nutrients), depth to rock, shrink and swell behavior (changes in soil volume due to amount of moisture), presumptive bearing value (ability of soil to sustain dead weight), and corrosion.
As a result of these limitations, major soil modifications (such as draining or excavating) are frequently necessary before areas can be developed. The modifications necessary to overcome these limitations may destroy valuable soil and vegetation. In addition, such modifications often destroy the valuable habitats that have evolved in response to the natural characteristics of the soil. An example would be the destruction of wetland vegetation when naturally wet soils are subjected to improperly designed artificial drainage.
Due to the fact that well-drained soils have little surface runoff and allow fairly easy water movement, they may serve as important recharge areas for ground-water systems. Riverine soils also serve valuable environmental functions. Riverine soils are important for water table recharge, flood control (by storing excess water), filtration of stormwater runoff, as transition areas along riverbanks, and for the support of hammock and freshwater marsh vegetation.
Agricultural use of soil
Agriculture is an important part of Alachua County's economy, and must be duly considered in all land use planning in the County. Urban development often conflicts with agricultural use, and can encroach on important farmland as development spreads. It is therefore necessary to determine those lands most suitable and important as farmland, and to provide for the protection of those lands from urban development.
Soil erosion is a problem during the construction activities of development. Topsoils, which are end products of thousands of years of natural buildup, are important to vegetation. Once carried off, not only are they lost to vegetation, but they often create siltation and sedimentation problems in the receiving waters. Soils, slopes, and erosion control as a result of non-agricultural development are reviewed and evaluated through development review and zoning application review processes.
Most of the soil erosion in Alachua County occurs in the northwestern and western portions of the County. A severe potential for water erosion occurs when the slope is greater than eight percent and the surface is void of plant cover and/or residue. Wind erosion is most prevalent in the months of January through April when the plant cover and/or residue is at a minimum.
The potential for significant erosion problems is minimized in Alachua County because of the lack of severe slopes and limited amount of cropland. Most potentially erodible soils in the County are in pasture land or natural vegetative cover.
The major mineral resources which have been, or may in the future be utilized for economic purposes are limestone, phosphate, sand, clay, peat and undifferentiated resources. Limestone and sand are the only mineral resources currently being mined in the County. Limestone has been mined extensively in western Alachua County for many years due to its availability near the surface and readily available transportation. Sand is mined chiefly in the southwestern and northeastern portions of the County. Peat presently is not being mined in the County, but evidence of potentially valuable deposits exists.
The following provides more information about the various mineral types found in Alachua County.
Limestone has been mined extensively in western Alachua County for many years. Several limestone quarries are currently in operation, notably northeast of Newberry. Many abandoned quarries are located throughout western Alachua County, forming steep-sided ponds where they are found. Limestone quarried in Alachua County primarily is used as a base coarse material for roadfill, as a raw material component of Portland cement, or in construction as crushed rock. Limestone products usually are distributed to nearby Florida markets and occasionally to South Georgia.
In the late 19th and early part of the 20th century, Alachua County produced significant amounts of hardrock phosphate; however, when pebble phosphate began to be mined at a substantially lower cost, hardrock phosphate mining began to decline. The industry continued through the mid 1960s when mining of the commodity in Alachua County finally ceased. Phosphate deposits in Alachua County are of a lower grade than those currently being mined in other parts of the State. As such, it currently is not economically feasible to mine the deposits found in Alachua County. However, as other Central and Northern Phosphate District areas become further depleted, deposits in and around Alachua County may take on increased significance. Should it become economically feasible to mine phosphate in Alachua County, the methods and technologies of land reclamation developed in the current mining districts will then become extremely important.
Sand is used primarily as fill material, construction ingredients, and in asphalt mixtures. The Natural Resource Conservation Service (NRCS) has determined that as many as 14 soil types located throughout the County are suitable as sources for road fill. Many of these areas are described by the NRCS as "probable" sources of sand based on compaction, processing, and other construction practices. Quartz sand occurrences in the County typically contain clay and silt. Mining is concentrated in the Brooksville Ridge area in the southwestern portion of the County and the Northern Highlands in the northeastern portion of the County.
Clay is present in the surface and near-surface sediments of Alachua County. The NRCS has identified several clay, sandy clay, clayey sand, and clayey loam soil types. One soil type, O'leno clay, is described as clay or clayey from its total depth to the surface. It is found primarily along the Santa Fe River. The NRCS rates this clay "poor" as a construction material. Many other clayey soil types are present in the County around Paynes Prairie, Levy Lake, Orange Lake, and the community of Island Grove. Aside from small extraction sites used by aboriginal peoples, clay has not been mined in Alachua County since the early 1920s when it was extracted near Campville. The extracted clay was used for the manufacture of a poor grade common brick. The quality of the clay present near Waldo and Hawthorne was determined to be suitable only as poor grade common brick as well. One test, however, indicated that the material could be suitable as ceramic clay. Due to the generally low grade of the clay present in the County it is not currently economically feasible to mine it. Because of the extent of clay deposits in the County, however, there may be future potential for clay production, based upon further exploration, and improvement in technologies for the utilization of lower grade materials.
Peat is comprised of partly decomposed organic matter (primarily plant matter) that accumulates in continuously wet areas. Other factors important in the accumulation of peat include topography and climate. Alachua County is well suited for the occurrence of peat deposits in several areas scattered throughout the eastern half of the County including the Santa Fe Swamp, Lake Alto Swamp, Newnans Lake, Lake Wauberg, and Lochloosa and Orange lakes. The Soil Conservation Service designated many other areas as having peaty soils including those mentioned above and Levy Lake, Ledwith Lake, Paynes Prairie and other smaller areas. Soil type associated with peat include Samsula, Shenks, Okeechobee, Terra Ceia and Ledwith. Peat is not being mined in Alachua County at present; however, evidence exists that areas with potential value for peat mining could be feasibly extracted. All Florida peats are generally used for horticultural purposes.
According to the Florida Geological Survey, a large portion of central and eastern Alachua County's surface and near-surface sediments are composed of sand, clayey sand, clay and organic muck. The Florida Geological Survey terms these "undifferentiated resources" and describes them as the largest area-wide deposits in the County with potential value as top-soil. The sand and clayey sand may be especially important as a source of fill in the County for many areas which are subject toflooding. Future investigations of this resource may lead to additional economic or industrial applications. While this is not considered a major mining resource, it does represent a vast area for a minor resource that may represent increasing economic activity.
Alachua County lies along the boundary of two major geomorphic divisions of the Florida peninsula, the Northern zone and the Central or mid-peninsula zone.
Features characteristic of the Northern zone include dry, steep walled sinks, abandoned spring heads, dry stream courses, and intermittent lakes and prairies, which were formerly broad shallow lakes.
The Central zone is comprised of ridges and broad valleys, the latter containing large shallow lakes. Within these divisions are three physiographic regions. These can be described as follows: a plateau region covering most of the Eastern and Northeastern part of the County; a Western plains region of karst (springs, caves and sinkholes) topography and occasional hills; and an area in the South central to Southeast part of the County containing flat-bottomed lakes and prairies.