INTRODUCTION
The Sand and Gravel Mining Industry is very active in Nebraska. There are 56 Sand And Gravel Mines in Nebraska. Because of safety standards and other policies. visiting a Sand and Gravel Mine is highly restricted. At this location you have the opportunity to see a Sand and Gravel Mine in operation without being on Mining property.
This EarthCache is located on a well maintained County Rd in Buffalo County. The Sand And Gravel Mine Overlook is located on Kea West Rd. South of Yanney Park in Kearney NE. The natural overlook is a result of an I-80 Overpass. As the road ramps up to go over I-80 one has a spectacular view of an active Sand and Gravel Mine. YOU ARE NOT ON MINING PROPERTY.
From this overlook you can see a Sand and Gravel Mine in operation. You are on public property and no permission is required for you to enjoy this vista and learn about the Sand and Gravel Mining. Rarely can you get this close to one of these mines and observe the full operation of the mine.
Please park in the nearby public area NE of the Coordinates and walk to the overlook location. There is considerable truck traffic during the business hours of the mine so it is best NOT to park on the shoulder of Kea West Rd. There is NO sign to indicate this is a mine overlook.
Geology of Sand and Gravel Mining
The use of sand and gravel as a commodity falls into two separate categories. Some is used in construction where it may be mixed with other materials or used as is. The second use is industrial where the sand and gravel are used in some way in the production of other materials. Because so much sand and gravel is consumed in each category, the United States Geological Survey (USGS) keeps track of sand and gravel consumption in these two separate categories. Sand, whether it is found on beaches or in rivers and streams, is mostly quartz (silicon dioxide, SiO2) grains. The weathering of rocks such as granite forms these quartz grains. In the process of weathering, the softer, weaker minerals in granite (such as feldspar) are weathered away. The more resistant quartz eventually is ground down in size, but does not break down chemically. In time, these quartz grains accumulate in rivers, streams, deltas and on beaches. Grains of other weathering-resistant minerals (such as garnet, rutile, ruby, sapphire, zircon, etc.) are often found in quartz sand as well. For some applications, it is the silica content (quartz) of sand that makes it so valuable. The silica itself is needed to make products such as glass. In addition, the physical properties of sand, particularly its abrasive property, make it useful for traction on icy roadways and railroads, and for sandblasting.
Sand and gravel are mined in various ways—mostly as open pits along ancient rivers. These deposits form as river channels change, with the sand and gravel particles left behind in the old bed. For example, the Susquehanna River in upstate New York has several gravel pits, as does the Platte River Valley in Nebraska; both contain thick gravel deposits left over from rivers that flowed through the areas before the ice ages some 10,000 years ago. The sand and gravel in these areas are mined in generally the same way. First, the vegetation and top soil are cleared to form a pit. Because the water table is so close to the surface near the river, the pit fills with water, becoming what is called a sandpit lake. The pit is then dredged with machines that extract the sand, gravel, and water. The slurry is then sent to a separator that sorts the sand and gravel according to size, with each different size used for specific applications.
The Geology of the Platte River, Source of Sand and Gravel Mining
The Platte River near Kearney can trace its evolution through geologic time. The central elements are the Platte River channels, islands, and bottomlands, which are flanked by terraces that step up away from the river to the north and south. Significant other elements of the landscape are eolian sand and loess deposits. The strata of this land area is made up of gravel, sand, silt, and clay beds from the ground surface to the top of the subsurface Tertiary Ogallala Group or Cretaceous formations. The sequence consists of Pliocene-, Pleistocene-, and Holocene-age strata that document the deposition of a veneer of alluvium by late Tertiary and Quaternary streams intermixed with and overlain by wind-blown loess. Various isopleth and structure maps illustrate the distribution and alluvial architecture of the sedimentary sequence, and support the interpretation of former positions of the Platte River.
A regional-scale study consisted of documenting the geologic history of the Front Range and adjacent mountains and depositional areas east of the mountains in Colorado, Wyoming, Kansas, and Nebraska from the end of the Cretaceous Period, about 65 million years ago, to the present. The structural and sedimentary history of the region is outlined, and a series of paleogeographic maps shows the development of the drainage system in the east-central Rocky Mountains and adjacent Plains. Ancestral South Platte, North Platte, and Laramie Rivers are recognized as early as the late Eocene, although the South Platte probably flowed to the southeast from the mountain front at that time. Deposits of the North Platte River are recognized on the west side of the Medicine Bow Mountains of Wyoming in the Miocene, and the presence of distinctive rock clasts indicates that the Laramie River flowed from the North Park area of Colorado northeast across a filled Laramie Basin and the Laramie Range of southeastern Wyoming in the Miocene. The present drainage system developed in the late Miocene to the Pliocene and included the capture and diversion of the South Platte River into its present channel. The combined North and South Platte Rivers deposited gravel and sand across Nebraska and flowed southeast from Kearney, Nebraska through the middle to late Pleistocene. Within the past 25,000 years the Platte River below Kearney was captured and diverted into its present course and confined there by bounding valley walls of loess.
REQUIREMENTS FOR LOGGING.
1) Observe the mining operation. How old is the rock that is mined here? Where did it come from?
2) Notice the large body of water. Where is this water coming from?
3) With the help of binoculars or by unaided observation, identify the different piles of material that is mined. Look for Sand, Gravel, River Stone, or other kinds of material around the lake.
4) Where you are standing is one of the results of mining. Many of the roads in Nebraska are composed of ROAD GRAVEL. From the edge of the road collect a sample of material.
a. What is the largest diameter stone.
b. What % is sand and other small particles.
5) To the South of these coordinates is a huge structure that’s foundation is made from material collected at a Sand and Gravel mine. What is it? Hint: “It is a composite material composed of water, coarse granular material (the fine and coarse aggregate or filler) embedded in a hard matrix of material (the cement or binder) that fills the space among the aggregate particles and glues them together.”
7). What do you think will happen to this mine when mining operations cease?
Please do not post your answers with your LOG, email them to me to verify your completion of the requirements. Feel free to post a picture of the mine.
For more information on Sand and Gravel Mining continue reading.
HOW SAND AND GRAVEL MINING WORKS
Sand and Gravel Mining Industry
When rocks erode out of the Rocky Mountains and are carried downstream by streams and rivers, they break apart making sand and gravel. The sand and gravel settles out of the water and form the river bed. As the river channel moves across the landscape, the sand and gravel (aggregate) deposits are left behind. In the Platte River valley, these deposits can be greater than 150 feet deep and often contain mammoth bones and teeth, bison bones and petrified wood.
Sand and gravel mining or aggregate mining is an important part of Nebraska's economy. Sand and gravel have a variety of uses including:
- road building
- construction
- concrete production
- landscaping
- glass manufacturing
- sand casting in iron and steel foundries
- snow and ice control
- petroleum extraction
Once an aggregate deposit is found, the first step in extracting the sand and gravel is to clear the surface of vegetation and topsoil and dig a pit. Since the water table is so close to the surface in Nebraska, the pit fills with water and forms a lake. A dredge is placed in the lake to extract the aggregate from the pit; the material is then carried by running water to a separator which separates the material by particle size. Different applications require different particle sizes, but typically, more fine sand is produced than can be sold. This excess sand is pumped back to the lake through a discharge or slurry pipe, forming the sandy nesting areas used by terns and plovers. In areas where most of the natural nesting habitat has been lost on the river (e.g., the Central and Lower Platte Rivers), sand and gravel mines play an important role in the conservation of terns and plovers.
After all of the usable aggregate has been extracted from a deposit and the mine is taken out of production, the land is sometimes reclaimed as agricultural land, but more often, the sandpit lakes are developed into lake shore housing developments, creating unique "beach front" property in Nebraska.
Resources:
http://ternandplover.unl.edu/info/sandgravelmining.asp http://www.mineralseducationcoalition.org/minerals/sand-and-gravel
http://www.answers.com/topic/how-are-sand-and-gravel-mined
http://pubs.usgs.gov/pp/pp1706/
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