EARTHCACHE REQUIREMENTS
Each cacher must send his/her own answers BEFORE logging a find. ... "Geocachers must complete the tasks before they log the EarthCache as found." (4.3. EarthCache logging tasks)
Enjoy the journey (learning adventure) as well as the destination (smiley earned). Remember to take only pictures and leave only footprints. To get credit for this Earthcache, complete the following tasks:
NOTE: Answers via message -and- log signature picture is required to post a find for this cache.
1. MESSAGE …. What direction of travel (Hwy 87) will you see the posted frog picture?
2. MESSAGE …. Observe the rock both front and back. a. Based on the colors, what minerals are present. / b. What is the difference in the amount of each mineral?
3. MESSAGE …. a. What are two differences between the posted picture and the same rock viewed traveling the opposite direction? / b. Explain what caused these differences.
4. LOG …. Post a picture of you or your signature item at another rock critter anyplace within Wind Cave National Park. This picture is your log signature. Name your critter and give location.
OPTIONAL - Please respect the time and effort involved in finding and creating this earthcache by adding A and B to your log.
A. JOURNEY OF THE MIND ... Science explains what we observe. Relate (in your own words) something you found interesting in the reading. This adds to your learning adventure and your log.
B. JOURNEY OF THE HEART ... Art shares our personal experience of what we see. Share something special you found on site, and why it is special to you ... prose / story / poem / picture. This is a memorable addition to your log and will make other hearts smile.
Journeys of Heart and Mind ...
Stories to Touch the Heart and Puzzles to Challenge the Mind / Rainbow Tree Story
BLACK HILLS
Granite is an intrusive igneous rock. Intrusive rocks form from molten material (magma) that flows and solidifies underground, where magma cools slowly. Eventually, the overlying rocks are removed, exposing the granite.
A granite intrusion created the Black Hills. This Frog Rock was created when some parts of the intrusion "burped up" .
GRANITE
Granite is composed of feldspar, quartz, and mica. Each of these mineral groups weathers according to its own chemical properties.
Feldspar weathering occurs via dissolution of all components into solution. The hardness of feldspar is 6.0-6,5
Quartz is the most stable of the common rock forming minerals. It is highly resistant to both chemical and mechanical weathering due to its high hardness and lack of cleavage. The hardness of quartz is 7.0
Mica is a type of clay mineral that is easily weathered. The hardness of mica is 2.5.
WEATHERING
Weathering is the breaking down of rock into smaller fragments. All rock weathers over time. Grains of sediment fall out. Cracks develop on the surface and deep inside. Weathering causes rocks to fracture, buckle, and crumble into soil and sediment. There are two types of weathering - mechanical and chemical. Based on the hardness of the minerals, differential weathering causes the softer minerals to weather much faster than the harder minerals. This results in formation of creative rocks like Frog Rock.
MECHANICAL WEATHERING
Mechanical weathering breaks apart rocks without changing their chemical composition. Each fragment and particle weathered away by a mechanical process retains the same characteristics as the original rock.
TEMPERATURE - Different minerals expand and contract at varying rates. Temperature changes occur in both day-night and seasonal cycles. Frost shattering or ice wedging is due to the expansion of ice.
WIND - The abrasive action of wind causes separation of rock particles from the parent rock.
WATER - The abrasive action of water also causes separation of rock particles from the parent rock.
GRAVITY - As rocks tumble downward, abrasion causes separation of rock particles from parent rock.
PRESSURE - Plants take root in cracks in rocks and wedge them open as they grow. This increases the surface area for continual weathering by plants, wind, and water. Even large rocks can be split apart.
Granite cools slowly with vertical and horizontal fissures forming within the rock mass as it contracts. The fissures expand to larger fractures as the rock cools further.
CHEMICAL WEATHERING
Chemical weathering occurs when water, air, and other substances react with the minerals in rock. In chemical weathering, the composition of the rock changes.
WATER - Water dissolves minerals in rocks, producing new compounds.
OXYGEN - Oxygen reacts with rocks, changing the color of rocks.
ACIDS - Produced when water reacts with the atmosphere.
LIVING ORGANISMS - Perform chemical reactions to obtain needed materials from rocks and soil. Plants give off organic acids as part of their life and decay processes. These acids help to break down rocks chemically. Decaying remains of dead animals in soil may form organic acids which, when dissolved in water, cause chemical weathering.
The main agent of chemical weathering in granite is hydrolysis due to mildly acidic rainwater. Feldspar and mica are most susceptible to chemical weathering.
RESOURCES ... Mechanical Weathering ... Chemical Weathering ... Biological Weathering ... Weathering of Granite ... Weathering Module