| Bfn Rock type | |
|---|---|
| Context | Bfn Natural temperate rocky shores |
| Type | Condition |
| Decompositie type | IOR |
Rock categories
Based on the way it formed, rock can be divided in three broad categories:
- igneous rock,
- sedimentary rock,
- metamorphic rock.
Igneous rock is formed when molten material in the form of magma wells up from the earth’s upper mantle or deep crust, cools and hardens into rock. Examples of igneous rock are granite (formed underground) and volcanic rock (formed above ground from cooled lava flows). Igneous rock makes up the bulk of Earth’s crust, although it is mostly covered with other, sedimentary rocks or soil.
Sedimentary rock is formed, when pre-existing rocks are weathered and eroded into small fragments, transported from their sources, and deposited into a body of water. Over time of thousands or millions of years this sediment hardens into sedimentary rock. For example, sandstone and shale are formed when the layers of weathered sediment are compacted under pressure, that has built up. Dolomite and limestone are also considered sedimentary rocks, although they are formed from the compacted shells and skeletons of dead organisms.
Metamorphic rock is produced when pre-existing rock is subjected to high temperatures and pressures, chemically active fluids, or a combination of these elements. Examples are anthracite, slate and marble (Miller, 2002).
Geology of the shore
Geology of the shore can play an important part in shaping the community composition on them. If the shore is composed of hard (weathering resistant) rock such as granite, slate and shale, it will in usually be steeper and less eroded, while softer, sedimentary rock shores tend to be heavily eroded and gently sloping. Additionally, metamorphic rocks have a large amount of cracks and crevices, as they are prone to having fractures (Murray et al., 2002; Little et al., 2010).
Non-carbonate substrates in general have a different community composition that carbonate rocks (limestone, dolomite, etc.), because many species, that settle on carbonate substrates by boring or etching, cannot effectively use these strategies on harder rock types. For example, endolithic algae and cyanobacteria generally are absent from non-carbonate rock microfilm. Nevertheless, organisms that prefer carbonate substrate, such as sea urchins, can still be present on non-carbonate rocks by attaching themselves to corrals, shells of mollusks or macro algae, for instance (Bromley and Heinberg, 2006).
According to investigation of shallow subtidal community composition on granite and limestone shores by Guidetti et al. (2004), epibenthic communities on limestone shores had a greater species richness and heterogeneity, while granite shores had a greater macro algae cover. Furthermore, fish species composition differed between the two types of substrate, which could be attributed to differences in refuge spaces and feeding possibilities, such as abundance of macro algae on granite, the various holes in limestone created by boring organisms, and the variations in benthic species richness.
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| Komt van | Type | Connectie type | Conditie | Waarde | Opmerkingen |
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| Bfn Surface roughness | Refers | rock type |
