Please message through the GC number and answers,
As soon as you have sent message you may log the find.
Once you have visited the location there is three questions –
1- What distinct colour lichen is present at the location? (it stands out)
2- What type of lichen is it? Fruticose, Foliose or Crustose?
3- In your opinion has the lichen caused erosion at GZ?
Below is information to assist in finding which type it is and information on rock erosion -
Lichen Facts
lichen is a composite organism that emerges from algae or cyanobacteria (or both) living among filaments of a fungus in a mutually beneficial (symbiotic) relationship. The whole combined life form has properties that are very different from properties of its component organisms. Lichens come in many colors, sizes, and forms. The properties are sometimes plant-like, but lichens are not plants. Lichens may grow like a tiny, leafless, branching shrub (fruticose), like it has leaves (foliose), like a crust of paint on a surface (crustose), or have other growth forms. A macrolichen is a lichen that is either bush-like or leafy. A microlichen is everything else. Here, "macro" and "micro" do not refer to size, but to the growth form. Common names for lichens may contain the word "moss" (e.g., "Reindeer moss", "Iceland moss"), and lichens may superficially look like and grow with mosses, but lichens are not related to mosses or any plant. Lichens do not have roots that absorb water and nutrients like in plants. Instead they produce their own food from sunlight, air, water, and minerals in their environment. They are not parasites on the plants they may grow on, but only use them as a substrate to grow on or in. Lichens occur from sea level to high alpine elevations, in a very wide range of environmental conditions, and can grow on almost any surface. Lichens are abundant growing on bark, leaves, mosses, on other lichens, and hanging from branches "living on thin air" (epiphytes) in rain forests and in temperate woodland. They grow on bare rock, walls, gravestones, roofs, exposed soil surfaces, and in the soil as part of a biological soil crust. They can survive in some of the most extreme environments on Earth: arctic tundra, hot dry deserts, rocky coasts, and toxic slag heaps. They can even live inside solid rock, growing between the grains. Some lichens do not grow on anything, living out their lives blowing about the environment. It is estimated that 6% of Earth's land surface is covered by lichen. Colonies of lichens may be spectacular in appearance, dominating much of the surface of the visual landscape in forests and natural places, such as the vertical "paint" covering the vast rock faces of Yosemite National Park.
Types of Lichen
Common groupings of lichen thallus growth forms are: 1. fruticose– growing up like a tuft or multiply branched leafless mini-shrub, or hanging down in strands or tassles, 3-dimensional with a nearly round cross section for its branching parts (terete), 2. foliose – growing in 2-dimensional, flat, leaf-like lobes that lift up from the surface, 3. crustose – crust-like, adhering tightly to a surface (substrate) like a thick coat of paint, 4. leprose – powdery, 5. gelatinous – jelly like, 6. filamentous – stringy or like matted hair, 7. Byssoid)- whispy, like teased wool, or 8. structureless. There are variations in growth types in a single lichen species, grey areas between the growth type descriptions, and overlapping between growth types, so some authors might describe lichens using different growth type descriptions.
When a crustose lichen gets old, the center may start to crack up like old-dried paint, old-broken asphalt paving, or like the polygonal "islands" of cracked-up mud in a dried lakebed. This is called being rimose or areolate, and the "island" pieces separated by the cracks are called areolas. The areolas appear separated, but are (or were) connected by an underlying "prothallus" or "hypothallus". When a crustose lichen grows from a center and appears to radiate out, it is called crustose placodioid. When the edges of the areolas lift up from the substrate, it is called squamulose. Some people who study lichens (lichenologists) group squamulose lichens separately from crustose lichens. These growth form groups are not precisely defined. Foliose lichens may sometimes branch and appear to be fruticose. Fruticose lichens may have flattened branching parts and appear leafy. Squamulous lichens may appear where the edges lift up. Gelatinous lichens may appear leafy when dry. Means of telling them apart in these cases are in the sections below.
Colour - Different colored lichens may inhabit different adjacent sections of a rock face, depending on the angle of exposure to light.
Lichens come in many colours. Coloration is usually determined by the photosynthetic component. Special pigments, such as yellow usnic acid, give lichens a variety of colors,. In the absence of special pigments, lichens are usually bright green to olive gray when wet, gray or grayish-green to brown when dry. This is because moisture causes the surface skin (cortex) to become more transparent, exposing the green photobiont layer. Different colored lichens covering large areas of exposed rock surfaces, or lichens covering or hanging from bark can be a spectacular display when the patches of diverse colors "come to life" or "glow" in brilliant displays following rain. Colour is used in identification. Color changes depending on when a lichen is wet or dry. Color descriptions when used for identification are based on when the lichen is dry. Dry lichens with a cyanobacteria as the photosynthetic partner tend to be dark grey, brown, or black.The underside of the leaf-like lobes of foliose lichens is a different color from the top side (dorsiventral), often brown or black, sometimes white. A fruticose lichen may have flattened "branches", appearing similar to a foiliose lichen, but the underside of a leaf-like structure on a fruticose lichen is the same color as the top side. The leaf-like lobes of a foliose lichen may branch, giving the appearance of a fruticose lichen, but the underside will be a different color from the top side.
Weathering facts
The role of lichens in rock weathering is of considerable interest to geomorphologists, both in relation to the actual processes of rock decay, and also in the formation of small-scale landforms. The distinguished geologist A. Geikie (1893) was probably the first to claim that lichens may have a protective effect. Viles & Pentecost (1994) presented field evidence from a quartzose sandstone in the Cedarberg Mountains (South Africa) in support of lichen protection of bedrock. Fiol et al. (1996) report an experimental study, which showed that loss of lithic material from a limestone surface was substantially reduced by lichen cover. The review of this topic by Viles & Pentecost (1994) draws attention to both the erosional and protective effects
of lichens. In the case of soluble rocks exposed directly to the atmosphere, erosion takes place by the solvent effect of rain falling directly on the rock surface. As the rock thus dissolves, the dissolved minerals are carried away by surface runoff, and the rock surface becomes lowered by solutional erosion. Calaforra (1998) has measured surface lowering of gypsum by erosion in southern Spain at 1·06 mm yr_1. Gypsum (CaSO4) is a rock material which is slightly soluble in water, to a concentration of 2·4 g l_1 (at 20_C). The effect of an insoluble object on the surface of such a rock is to act as a local umbrella, and thereby prevent the solvent from coming into contact with the rock surface. In this case, the surrounding rock, still exposed to the atmosphere, continues to be lowered, whilst the protected area stands increasingly proud of the surrounding bedrock surface, gradually emerging as a significant area of local relief. This study presents observations on lichens which have colonized an exposed gypsum surface, and provide clear evidence of substratum protection. This has the geomorphological effect of creating topography at the millimetre to centimetre scale. At the study site the gypsum bedrock forms gently sloping planar surfaces. On these surfaces lichens grow on, and are coincident with, small roughly conical or rounded mounds which stand proud of the surrounding gypsum surface. The gypsum forming the mounds is integral with the bedrock beneath. Since all lichens are associated with a mound, and no mounds exist without a lichen cover, there is evidently a causal relationship between lichen presence and the existence of a mound.
study has provided strong evidence that lichens can protect a soluble bedrock from subaerial weathering by chemically aggressive rainwater. As a consequence small-scale landforms have been created, which differ in form according to whether or not the lichen suffers central decay. There is a need for determination of lichen growth rates in such environments, by means of the calibration of lichen diameter and age (Mottershead 1980). One approach to achieving this is to measure lichen size on independently dated surfaces of similar substrata. In the current absence of such calibration, it is only possible to calculate only relative rates of lichen growth and surface lowering or to estimate absolute values by using rates of erosion from other regions. When appropriate calibration becomes available, however, then the relationships described here might provide a valuable tool for the determination of rates of erosion in these soluble terrains.