A Little Slice of King's Row EarthCache
Hidden : 4/16/2018
Difficulty:
1.5 out of 5
Terrain:
1.5 out of 5

Size: Size: other (other)

Join now to view geocache location details. It's free!

Watch

How Geocaching Works
Looking for a different adventure?

Please note Use of geocaching.com services is subject to the terms and conditions in our disclaimer.

Geocache Description:


This Earthcache examines the effects of weathering on differing types of rock. As this cache is located along the right of way of a road that can be busy at times, be sure to pull completely onto the shoulder of the road near the posted coordinates. Keep an eye on the kids if they help.

Standing at the posted coordinates, you are presented with an exposed road cut made years ago. Two types of rock are present here (dolomite and shale) in very distinct layers, but one is noticeably more weathered than the other. Why?
What is Weathering?

Weathering is the action of certain conditions in altering the color, texture, composition, or form of exposed objects; specifically, the physical disintegration and chemical decomposition of earth materials at or near the earth's surface.

There are three basic classifications of weathering processes – physical, chemical, and biological weathering – and each can involve biological or non-biological components.

Physical weathering

Physical weathering is caused by the effects of changing temperature on rocks, causing the rock to break apart. The process is often assisted by water. There are two main types of physical weathering:

Freeze-thaw - This occurs when water continually seeps into cracks, freezes and expands, eventually breaking the rock apart.

Exfoliation - This process engages as cracks develop parallel to the land surface a consequence of the reduction in pressure during uplift and erosion.

Physical weathering happens especially in places places where there is little soil and few plants grow, such as in mountain regions and hot deserts, but it can happen in almost all climates. The procss occurs either through repeated melting and freezing of water (mountains and tundra) or through expansion and contraction of the surface layer of rocks that are baked by the sun (hot deserts).

Chemical weathering

Chemical weathering is caused by rain water reacting with the mineral grains in rocks to form new minerals (clays) and soluble salts. These reactions occur particularly when the water is slightly acidic. These chemical processes need water, and occur more rapidly at higher temperature, so warm, damp climates are best. Chemical weathering (especially hydrolysis and oxidation) is the first stage in the production of soils. There are different types of chemical weathering, the most important being:

Solution - The removal of rock in solution by acidic rainwater. In particular, limestone is weathered by rainwater containing dissolved CO2, (this process is sometimes called carbonation).

Hydrolysis - The breakdown of rock by acidic water to produce clay and soluble salts.

Oxidation - The breakdown of rock by oxygen and water, often giving iron-rich rocks a rusty-coloured weathered surface.

Biological weathering

Biological weathering occurs when living organisms contribute to the weathering process. Some examples include:

• Trees put down roots through joints or cracks in the rock in order to find moisture. As the tree grows, the roots gradually pry the rock apart.

• Some animals bore into rocks for protection, either by scraping away the grains or secreting acid to dissolve the rock.

• Bacteria, algae and lichens produce chemicals that help break down the rock on which they live, so they can get the nutrients they need.
The Properties of Different Stones at this Site

This site presents the viewer with examples of shale and dolomite, the latter more precisely known as the Jefferson City Dolomite.

Dolomite

Dolomite is both a rock and mineral name, e.g., the rock dolomite is made up of an aggregate of particles of the mineral dolomite. Chemically, the mineral dolomite is a calcium-magnesium bicarbonate and thus differs from limestone in having magnesium addd to the chemical formula. Dolomite contrasts with limestone in effervescing or "fizzing" less vigorously when tested with hydrochloric acid.

Many laymen do not distinguish between limestone and dolomite, and the dolomites which are especially wide-spread in the Ozark region are often colloquially referred to as "limerock."

Dolomite and limestone are very close relatives, and the percentage of magnesium may determine whether the rock is a limestone, a dolomitic limestone, a calcareous dolomite, or a true dolomite. Both limestone and dolomite are especially vulnerable to the dissolving action of moving waters, and are two rocks in which caves, sinkholes, and large spring in Missouri are most commonly found.

Shale

Shale is a fine-grained, laminated sedimentary rock consisting of silt- and clay-sized particles. Shale is the most abundant of the sedimentary rocks, accounting for roughly 70% of this rock type in the crust of the Earth. Shales are often found within layers of sandstone, limestone, or dolomite. They typically form in environments where muds, silts, and other sediments were deposited by gentle transporting currents and became compacted. Many shales occur in extensive sheets several feet thick.

Shales characteristically consist of at least 30% clay minerals and substantial amounts of quartz. They also contain smaller quantities of carbonates, feldspars, iron oxides, fossils, and organic matter. Some organic-rich shales, called oil shales, contain kerogen (a chemically complex mixture of solid hydrocarbons derived from plant and animal matter) in large enough quantities to yield oil when subjected to intense heat.

Shales typically have a laminated structure and are fissile; i.e., they exhibit a tendency to split into thin layers that are usually parallel to the bedding-plane surface. However, such physical properties as permeability and plasticity are largely dependent on the grain sizes of the minerals within the rock. The color of shale is determined primarily by composition. In general, the higher the organic content of a shale, the darker its color. The presence of hematite and limonite gives rise to reddish and purple coloring, while mineral components rich in ferrous iron impart blue, green, and black hues. Calcareous shales (those having a large percentage of calcite), on the other hand, are light gray or yellowish.
The Earthcache

Stand at the posted coordinates, face north and consider the exposed road cut before you. Note how much it’s weathered and the composition of the rocks in the cut. There is a distinct difference in the weathering of the layers, isn't there? After you have studied the what's before you, answer the questions below and email those answers to me through my profile.

Any logs that do not follow these requirements will be deleted.

1. How many distinct rock layers do you see at ground zero?

2. What specific kind of weathering do you think has played the most part here?

3. Examine the texture of the flat surfaces of each kind of rock. Is one smoother than the other? Is one seemingly more brittle? Does one have more cracks or other textures that would allow water to seep in?

4. There are layers of dolomite and shale before you. Which one is most eroded? Given what we know about the composition of the two rocks, why do you think this is so?

5. Look left (west) and right (east) from where you're standing. You will see that certain layers have eroded quite deeply into the rock face. Approximately how deep is the deepest spot you see?

6. Looking left, you will see some large rocks have fallen down. Do you think that the weathering procss you've seen so far is mainly to blame for this collapse, or is another type of weathering mentioned above partially to blame as well?
Taking a photo of yourself with either marker or both of them behind you would be nice, but it is not required.

Additional Hints (No hints available.)



Advertising with Us

Inventory

There are no Trackables in this cache.

View past Trackables

What are Trackable Items?

Bookmark Lists

View all bookmark lists...