Shale
Is a fine-grained, clastic sedimentary rock composed of mud that is a mix of flakes of clay minerals and tiny fragments (silt-sized particles) of other minerals, especially quartz and calcite. The ratio of clay to other minerals is variable. Shale is characterized by breaks along thin parallel layering or bedding less than one centimeter in thickness, called fissility.
Limestone
Is a sedimentary rock composed largely of the minerals calcite and aragonite, which are different crystal forms of calcium carbonate (CaCO3). Limestone makes up about 10% of the total volume of all sedimentary rocks. The solubility of limestone in water and weak acid solutions leads to karst landscapes, in which water erodes the limestone over thousands to millions of years.
Sandstone
(sometimes known as arenite) is a clastic sedimentary rock composed mainly of sand-sized minerals or rock grains. Most sandstone is composed of quartz and/or feldspar because these are the most common minerals in the Earth's crust. Like sand, sandstone may be any colour, but the most common colours are tan, brown, yellow, red, grey, pink, white and black. Since sandstone beds often form highly visible cliffs and other topographic features, certain colours of sandstone have been strongly identified with certain regions.
Fireclay
A heat-resistant, clay-rich sedimentary rock containing a high percentage of aluminum oxide Fireclay is a clay-rich sedimentary rock that contains a high percentage of aluminum oxide, which makes it very resistant to the effects of high temperatures. It is usually massive (not laminated or layered) and fractures into blocky or irregular fragments. Common colors include buff, yellow, red, green or brown. However, good, useable fireclay is usually white, cream-colored, gray, or almost black.
Ore
An ore is a type of rock that contains minerals with important elements including metals that can be extracted from the rock at a profit. The ores are extracted through mining; these are then refined (often via smelting) to extract the valuable element(s).
Iron Ore
Iron ores are rocks and minerals from which metallic iron can be economically extracted. The ores are usually rich in iron oxides and vary in color from dark grey, bright yellow, deep purple, to rusty red. The iron itself is usually found in the form of magnetite (Fe3O4), hematite (Fe2O3), goethite (FeO(OH)), limonite (FeO(OH).n(H2O)) or siderite (FeCO3).
Rock Shelter
A rock shelter is a shallow cave-like opening at the base of a bluff or cliff. Rock shelters form because a rock stratum such as sandstone that is resistant to erosion and weathering has formed a cliff or bluff, but a softer stratum, more subject to erosion and weathering, lies just below the resistant stratum, and thus undercuts the cliff.
Karst topography
Karst topography is a geological formation shaped by the dissolution of a layer or layers of soluble bedrock usually carbonate rock such as limestone or dolomite. Subterranean drainage may limit surface water with few to no rivers or lakes. Many karst regions display distinctive surface features, with sinkholes being the most common. However, distinctive karst surface features may be completely absent where the soluble rock is mantled, such as by glacial debris or confined by one or more superimposed non-soluble rock strata. Some karst regions include thousands of caves, although evidence of caves large enough for human exploration is not a required characteristic of karst.
Types and formation
A cave or cavern is a hollow place in the ground, especially natural underground space large enough for a human to enter. Caves form naturally by the weathering of rock and often extend deep underground.
solution caves
Solutional caves are the most frequently occurring caves and such caves form in rock that is soluble, such as limestone, but can also form in other rocks, including chalk, dolomite, marble, salt, and gypsum. Rock is dissolved by natural acid in groundwater that seeps through bedding-planes, faults, joints and so on. Over geological epochs cracks expand to become caves and cave systems.
How caves form
Cave formation begins when rainwater absorbs carbon dioxide as it falls through the atmosphere. Rain water must have carbon dioxide to become acidic. It must be acidic to chemically react to the limestone bedrock. Rainwater is absorbed by the soil into the ground.
As rainwater comes through the soil it absorbs more carbon dioxide that is being produced by plants that are dead. This changes the ground water to a weaker form of carbonic acid (H2O + CO2 = H2CO3). As it travels down through the ground it comes to solid rock. When the rock is limestone or dolomite caves can form.
The water reacts chemically with limestone and slowly a larger and larger space will form. This happens because the rocks are made of calcium carbonate (CaCO3). This is what you call chemical erosion.
As the space becomes larger and larger the water can flow through. As it flows it erodes. Physical erosion washes away rock and sand. This is what makes a cave larger and forms an underground stream. Finally over hundreds of thousands of years or even millions of years the cave is formed.
**Logging requirements**
DO NOT POST ANSWERS IN YOUR LOG.
Send the following answers to me via email.
- The text "GC537RF Crumby Situation" on the first line
- Is this a cave or rock shelter?
- How high is the bigger cave/shelter?
- Do you see evidence of a stream, creek or spring that might be intermediately flowing between the rocks and the ground?
- Based on your answer from #4; does this change your classification of this feature? And if so what is it now?
- What do you think the rock is made of?
- How wide is the primary pillar?
- See waypoint "Iron" Where did this ore that was converted to iron come from?
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