Weathering & Erosion at Dixon Springs EarthCache
Weathering & Erosion at Dixon Springs
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This Earthcache will take you to a rock outcrop near the Dixon Spring Cemetery where you will explore the concept of Weathering and Erosion. Access is best if you park at the cemetery and make your way past the northeast corner of the lot. While there grab the geocache "Quiet Repose". At request of property owner, please visit only during daytime hours.
What You Need and Be Aware Of
This location provides many examples of Weathering and Erosion. Some of these are very observable and some are not. We will focus on those easily seen. You will need a keen observation skills, and study the tables below before going to the site. Be careful around and on the rock formation. Do not pull on any loose rocks.
What You Will Be Doing In Order to Log This Find
A. Click on my profile and e-mail the answers for the following tasks. Do not post your answers when you log in your find. Logs which do not meet the requirements will be deleted.
(1) Explore rock outcropping and be especially alert to the signs of weathering and erosion on and around the rock formations.
(2) Physical Weathering
(a) Abrasion is occuring on this outcropping. Describe the evidence that this has occured.
(b) Which process frost wedging/biological or abrasion is causing most of the physical weathering on this outcropping?
(3) One type of Chemical Weathering is very observable on this outcropping. Which is it and how do you know?
(4) Erosion
(a) Which of the three types of mass wasting is predominant in the area of the outcropping?
(b) In your opinion what agent caused the abrasion seen at this sight - water, wind or ice?
(5) Describe how differential weathering is occuring at this location.
B. Optional, though greatly apprecited. Take and log a picture of you (and your group) standing near the rock formation.
Erosion and Weathering are the natural processes in which rocks, soils and minerals as well as artificial materials are broken apart, moved and redeposited. Weathering is the breaking down of those rocks, soils and minerals into smaller pieces and/or converting them into other materials by physical or chemical means. Differential Weathering is variation in the rate of weathering and erosion. Rocks that are harder than their neighbors will seem to grow out of the ground, as if that caused the outcrops here. In reality, the rocks in the outcrop are largely staying in place, while the softer rocks in the ground around them are eroding away.
Physical weathering are the processes that causes the physical disintegration of rocks. The primary process in physical weathering is abrasion, however, physical weathering can be occur due to temperature pressure frost etc.
Abrasion
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Thermal Stress
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Frost Wedging
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Physical Biological Weathering
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Agents carried by wind, water, and glaciers removes the upper layer of the rock by friction
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Results from the expansion and contraction of rock due to temperature changes which stresses and fatiques the rock; primary agent of weathering in deserts
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Caused by water entering cracks in rocks and expands upon freezing which stresses and fatiques the rock; occurs in areas with seasonal/daily temperature changes
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Seedings and roots penetrate crevices exerting physical pressure as well as providing a pathway for water and chemical infiltration
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Chemical weathering changes the composition of rocks, often transforming them when water interacts with minerals to create various chemical reactions. Chemical weathering is a gradual and ongoing process as the mineralogy of the rock adjusts to the near surface environment. New or secondary minerals develop from the original minerals of the rock. In this the processes of oxidation and hydrolysis are most important.
Oxidation
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Hydrolysis (Dissolution)
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Carbonation
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Organic Acid
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Acid Precipitation
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takes place when oxygen reacts with earth minerals; causes metals to turn brownish to reddish
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Water reacts with minerals driving them into solution; these are them leached to lower layers as water moves through the rock
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involves the combination of carbon dioxide and water forming a weak carbonic acid; this acid reacts with the minerals driving them into solution where they are leached
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acids produced by living things: plants, lichens, moss, fungi, animals reacts with minerals producing new elements that dissolve in water easily
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acidic rain, sleet, or snow that contain high concentrations of acids from sulfur and nitrogen oxide pollution in the atmosphere;
this acid reacts with the minerals driving them into solution where they are leached
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Erosion is the actual transporting of bits and pieces of rock by water, wind, glaciers, by down-slope mass movement, or by living organisms, such as burrowing animals.
Gravity
(mass wasting)
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Landslides, Rockfalls, or Mudslides
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Slumps
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Creeps
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any perceptible down-slope movement of rock and sediments, due to the force of gravity
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happens on steep hillsides, occurring along distinct fracture zones, often within materials like clay that, once released, may move quite rapidly downhill. They will often show a spoon-shaped depression, in which the material has begun to slide downhill |
the slow movement of soil and rock debris by gravity which is usually not perceptible except through extended observation |
Water
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Splash Erosion
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Sheet Erosion
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Rill Erosion
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Gully Erosion
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Stream Erosion
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Shore Erosion
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| the detachment and airborne movement of small soil particles caused by the impact of raindrops on soil. |
the detachment of soil particles by raindrop impact and their removal downslope by water flowing overland as a sheet instead of in definite channels or rills |
the removal of soil by concentrated water running through multiple little streamlets |
occurs when water flows in narrow channels during or immediately after heavy rains or melting snow |
occurs with continued water flow along a linear feature; includes valley formation and bank erosion
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occurs on both exposed and sheltered coasts, primarily occurs through the action of currents and waves but sea level (tidal) change can also play a role |
Ice
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caused by the movement of ice, typically as glaciers; occurs through abrasion/scouring, plucking (rock breaking off), and ice thrusting |
Wind
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causes small particles to be lifted and therefore moved to another region (deflation); these suspended particles may impact on solid objects causing erosion by abrasion.
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1. This Earthcache is placed with permission of the property owner.
2. Please exercise caution when around the rock formation. There is no need to climb on the rock formations.
3. Please guage you own abilities carefully. Do not attempt this earthcache if it seems hazardous.
Additional Hints
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Treasures
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