This earthcache was set up for SEMAG Meet & Greet #100 - The Centennial Event (GCA56E4). It is located along the Cedar Swamp trail in the Bioreserve. Special thanks to groopsoop for the help with the earthcache description!
If you look carefully as you pan this swamp, you’ll notice that there are areas of a rusty brown or orange color, especially toward the edges where decaying vegetation collects. You might also see an oily film floating on the surface in the same area. This is evidence of the presence of
bog iron.
Definitions:
Bog Iron: Iron deposits that develop in bogs and swamps.
Ferric Hydroxide: a compound consisting of iron and oxygen.
Floc(cule): a small clump of material that resembles a tuft of wool or hairball.
Ingot: mass of metal cast into a size and shape such as a bar, plate, or sheet convenient to
store, transport, and work into a semifinished or finished product.
Microbes: Microorganisms: organisms of microscopic size, which may exist in a single-celled
form or as a colony of cells.
Oxidation: Oxidation occurs when the oxidation state of a molecule, atom or ion is increased. Often, the oxidizing agent is oxygen, as is often the case with bog iron.
Smelting: A process used to extract metals from their ores by heating them to high
temperatures beyond their melting points.
Above is a photo of Cedar Swamp. Do you see any evidence of bog iron in the photo?
Bog iron is a form of impure iron deposit that develops in bogs or swamps by the oxidation of iron. It develops in clumps that range in size from that of a pea to a large basketball-sized boulder. (It takes about 20 years to make pea-sized clumps.)
The requirements for the creation of bog iron include:
1. water with dissolved iron,
2. an acid environment,
3. an anaerobic (deoxygenated) environment for microorganisms feeding on decaying organic matter,
4. proper temperature range, and
5. an environment where there is exposure to a sufficient level of oxygen to oxidize the dissolved iron.
Iron-bearing groundwater typically emerges as a spring and the iron in it forms ferric hydroxide upon encountering the surface.
Bog iron often consists of several minerals: goethite, magnetite, and stained quartz. This causes the swamp’s plants to become heavily encrusted with a light-orange floc of iron oxyhydroxide near the point of oxygen gas released from the plants. Factors such as local geology, rock mineralogy, ground-water composition, and geochemically active microbes and plants influence the formation, growth, and persistence of iron bogs.
Did you know?
- Not far from here is the Iron Mine Creek on Tremont Street in Rehoboth? Years ago thiswas an active bog iron mining area. The large cranberry bog there and many others in the area were originally bog iron mines.
- In colonial days, iron was so valuable that it was often used as wages?
- Bog iron was placed in furnaces for smelting? The resulting product was called ‘pig iron’. Pig iron is iron with a high carbon content. Pig iron is made by smelting iron ore, such as bog iron, in a blast furnace. (It’s called pig iron because when being cast, each ingot being cast looks like a Piglet suckling milk from a sow.)
Logging Requirements
1) Do you see any evidence of bog iron or form of discoloration in the swamp?
2) What geological factors do you think would lead to the creation of bog iron in the swamp?
3) Please upload a photo of you or a geocaching item at or near GZ as a proof of visit.