Blackhawk Spring EarthCache
In Iowa, United States
Size:  (not chosen)
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This EarthCache will bring you to Crapo (pronounced Cray-Po) Park which is located in Burlington Iowa.
Blackhawk Springs was formed by the movement of the Ice Age Glaciers. As the glaciers flowed over the area, it softened and lifted out blocks of rock, which were moved out of the area by the moving ice. (This process is known as plucking). The rate of glacier erosion is variable and is controlled by several factors. Some of these factors include: Velocity of glacial movement, thickness of the ice, shape and hardness of rock fragments contained in the ice at the bottom of the glacier, and permeability and water pressure at the glacier base.
As you can see, the glaciers excavated the side of the hill where the spring is located. The spring was formed because there was a natural flowing body of ground water at or below the local water table where the subsurface material was saturated with water. A spring is formed as a result of an aquifer being filled to the point where the water overflows onto the land surface.
Springs are natural flows of water from the ground or from rocks, representing an outlet for the water that has accumulated in permeable rock strata underground. Some of the water that falls as rain soaks into the soil and is drawn downward by gravity to a depth where all openings and pore spaces in the rock or soil have become completely saturated with water. This region is called the zone of saturation, and the water it holds, groundwater. The upper surface of the zone of saturation is called the water table. Above the water table lies the zone of aeration, where the pore spaces in the soil are quite dry and are filled with air. When the upper surface of the groundwater (water table) intersects a sloping land surface, a spring appears. The occurrence of springs is closely related to the geology of an area. If an impervious layer of rock, such as a clay deposit, underlies a layer of saturated soil or rock, then a line of springs will tend to appear on a slope where the clay layer outcrops. Igneous rocks are also impervious to water, yet they are often extensively fractured, and springs commonly appear where these fractures come to the surface. Fractures in limestone are often enlarged by the dissolving action of groundwater, forming small underground channels and caves. Where these channels outcrop, springs are likely to be found.
In order to receive credit for this EarthCache, you will need to take a couple of measurements and do a little analysis of one of your findings.
1.At the posted coordinates, please measure the water's temperature.
2. At the posted coordinates, please measure the water's pH. pH Testing strips can be obtained from any pool supply store.
3. Why do you think the water is either acidic or basic?
(e-mail the answers to these three questions to me.)
4.When you log this EarthCache, if you would like, please upload a picture of yourself/team with your GPS clearly visible at the posted coordinates.
(No hints available.)
Last Updated: on 4/5/2015 3:30:29 PM Pacific Daylight Time (10:30 PM GMT)
Coordinates are in the WGS84 datum