Metcalf Rock Karst Spring EarthCache
Hidden : 4/15/2013
Difficulty:
1.5 out of 5
Terrain:
1.5 out of 5

Size: Size: other (other)

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Geocache Description:

Things you'll need for this Earth Cache.
1. Container of known size.
2. Stop Watch.
3. Thermometer.
4. GPSr.
5. Yourself.

Metcalf Rock/ Niagara Escarpment

Metcalfe Rock, found in the Kolopore Uplands is part of the Niagara Escarpment. The unique karst rock formations make this a favorite location for hiking, rock climbing and caving. A hike along the marked trails will show classic Karst formations (fissures, springs, dry and blind valleys) and provide access to a number of Karst caves.

The Niagara Escarpment has origins dating back some 430 to 450 million years ago. During this time it was covered beneath a large ancient sea, which lay in a saucer shaped depression in the state of Michigan, now known geologically as the Michigan Basin. Rivers flowing into this sea carried sand and clay, which were deposited as sediment. The sea flourished and became rich with plant and animal life, which eventually died, and over time became compressed into many layers of sedimentary rocks. The ancient sea began to become shallower as the Michigan Basin began to rise, due to disturbances in the Earth’s crust.



During the next millennia the seas withdrew, leaving the earth’s surface exposed. Pre-glacial rivers and streams began carving out the body of the plain, creating valleys and ridges. A series of four Ice Ages, occurring within the past two million years, covered North America with thick ice sheets. In time the glaciers began to retreat, eroding away the soft layers of the Escarpment and leaving the hard dolomite limestone exposed at its surface. The great ice sheets also widened the valley’s floor, making its sides more steep, and created caves and cliffs. Still today ice, wind, and water continue to erode the rock that makes up the Escarpment, changing its face in an unending process.

The abundance of dolostone and limestone in Niagara Escarpment rock makes chemical weathering an important process in shaping the area landscape. The calcium and magnesium carbonates composing these rocks readily dissolve in the weak acid conditions common to most natural water to create sinkholes, caves, springs and other features of Karst Topography readily found here.

What is a Karst?

Karst is a type of landscape, and also an aquifer type. Karst areas consist of solid but chemically soluble rock such as limestone (most important) and dolomite, but also gypsum, anhydrite and several other soluble rocks. The chemical reaction describing limestone dissolution is:

CaCO 3 + CO 2 + H 2O = Ca 2+ + 2HCO 3 -

Karst landscapes show characteristic landforms caused by chemical dissolution, such as karren (crevices and channels, tens of cm wide), dolines and sinkholes (closed depressions, tens of m in diameter) and poljes (large depressions with flat floor, several km 2 or more). Streams and rivers sinking underground via swallow holes are also frequent.







What is a Karst Aquifer

Karst aquifers are characterised by a network of conduits and caves formed by chemical dissolution, allowing for rapid and often turbulent water flow. A karst aquifer may be present even when there are no discernible karst landforms at the land surface, and even when there are no known and accessible caves.



Why are karst aquifers important?

Hundreds of millions of people worldwide live in karst areas and are supplied by drinking water from karst aquifers. These aquifers include valuable freshwater resources, but are sometimes difficult to exploit and are almost always vulnerable to contamination, due to their specific hydrogeologic properties.

Therefore, karst aquifers require increased protection and application of specific hydrogeologic methods for their investigation. Other problems frequently encountered in karst areas include: soil erosion and rock desertification, leakages of channels and reservoirs, collapse of underground cavities and formation of sinkholes, and flooding. Resolution of these problems requires involvement of karst hydrogeology experts.

Hydrogeologic characteristics of karst aquifers

Evolution : Karst aquifers form by flowing water containing carbon dioxide (CO 2) which dissolves carbonate rocks. Therefore, there is a close relation between aquifer evolution, the formation of caves (speleogenesis) and groundwater flow.

Individuality : Although there are many similarities among different karst systems, every karst system is also a special case and generalisation is difficult.

Heterogeneity : The properties of karst aquifers greatly vary in space. There may be large quantities of water in a cave, but a borehole a few metres away may be completely dry.

Anisotropy : The aquifer hydraulic properties depend on the orientation of geologic fabric elements; for example, the hydraulic conductivity is typically high in the direction of large fractures and conduits, but may be low in other directions.

Duality of recharge : Recharge water may originate from the karst area itself (autogenic recharge) or from adjacent non-karstic areas (allogenic recharge). Duality of infiltration : Infiltration occurs through the soil and unsaturated zone (diffuse infiltration), and may also be concentrated via swallow holes/sinks (point infiltration).

Duality of porosity and flow : There are two or even three types of porosity in karst aquifers: intergranular pores in the rock matrix, common rock discontinuities such as fractures (fissures) and bedding planes, and solutionally-enlarged voids such as channels and conduits developed from the initial discontinuities. Whereas groundwater flow in the matrix and small fissures is typically slow and laminar, flow in karst conduits (caves) is often fast and turbulent.

Variability : The water table in karst aquifers can sometimes fluctuate 10s or even 100s of metres in short periods of time, and karst springs typically show rapid variations of discharge and water quality.

Difficulties in using karst groundwater

Vulnerability to contamination : Contaminants can easily enter karst aquifers through thin soils or via swallow holes (sinks). Inside the aquifer, contaminants can quickly spread over large distances, due to rapid and turbulent flow in the conduit network. Natural attenuation processes, such as filtration and retardation, are often less effective than in other aquifers.

Access to water : Due to the high degree of heterogeneity, it is difficult to drill a successful water supply well into a karst aquifer. In mountainous karst regions, the water table is often very deep below land surface, sometimes 100s of metres. Karst springs are typically very large, but also quite rare. Even in humid regions, there are often large areas without any accessible water because surface water runoff and rainfall quickly infiltrate into the karst aquifer and flow to distant springs.

Variability : Water suppliers prefer water sources with stable discharge and water quality, but karst springs often show high variations of both. Periods of excellent water quality may be interrupted by short contamination events.

Magnitude

There is a simple equation for measuring the magnitude of a spring. In order to do so your must capture the rate at which water is exiting the spring.

Magnitude Flow (ft³/s, gal/min, pint/min) Flow (L/s)
1st Magnitude > 100 ft³/s 2800 L/s
2nd Magnitude 10 to 100 ft³/s 280 to 2800 L/s
3rd Magnitude 1 to 10 ft³/s 28 to 280 L/s
4th Magnitude 100 US gal/min to 1 ft³/s (448 US gal/min) 6.3 to 28 L/s
5th Magnitude 10 to 100 gal/min 0.63 to 6.3 L/s
6th Magnitude 1 to 10 gal/min 63 to 630 mL/s
7th Magnitude 1 pint to 1 gal/min 8 to 63 mL/s
8th Magnitude Less than 1 pint/min 8 mL/s
0 Magnitude no flow (sites of past/historic flow)


To Log This Cache

In order to log this cache you will need to bring a container that can be used as a measuring device and some sort of stop watch and a thermometer. Navigate to the posted coordinates and provide the following:

1) Using your container and stop watch measure the rate of flow from the black pipe. Using the chart listed in the cache description tell me what magnitude of flow this spring is.(Please do not post with your log. E-mail info.)

2) Take a temperature reading of the water coming out of the pipe.(Please do not post with your log. E-mail info.)

3) Using your GPS provide me with the elevation above sea level in meters.(Please do not post with your log. E-mail info.)

4) Take a picture of yourself or GPSr with the spring in the background.(Optional)



This cache has been placed by a Central Ontario Geocacher!

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