eHabitat – Salvati Pesterile

Intrări în habitatul 8310 cu dezvoltarea peste 100 m
Situl Natura 2000 Cheile Nerei – Beușnița

Habitat 8310

Caves not open to the public and hosting normally protected animal species

What are the caves?

More broadly, the cave is a natural cavity formed by karstic rocks (mainly limestone, but can be also another rocks) of a size enough that a man could enter into it. Some sources declare a cavity to be cave, if it is also considered their length (over 7 meters).

The caves are part of broader systems of underground holes that includes also inaccessible passages for humans. These systems often have much greater length than caves and provide links (connections) between the largest gaps by circulation of underground water.

The karstification

Often, the caves are formed by double action of corrosion and erosion of groundwater in limestone or rocks containing carbonate.

The karstification is the process by which water containing CO₂, actually an acidic solution, is acting on limestone and determine dissolution (corrosion) thereof, by incorporating continuous the calcium ions. Increased water acidity increases its corrosivity.

Water seeps into the limestone by numerous cracks and fractures. Therefore, most caves are developing along the main fracture in a given limestone region. The place where a creek or river is lost on underground is called ponor, also sink or sinkhole.

Karst topography is a landscape formed from the dissolution of soluble rocks and it is characterized by underground drainage systems with sinkholes and caves. Most often these are limestones, but there may be other types of rocks where different processes have created natural hollow places (eg. volcanic rocks or massive salt).

Types of Caves

Caves are often classified by origin (i.e. after the formation) after rock after they grow or form. Overall classification has a purpose more informal and is quite flexible.

By origin: the caves can be formed by dissolution, volcanic activity, erosion, melting ice, action or tectonic stress accumulation of rock fragments from the slopes.
By the type of rock or material which were formed: limestone caves in the volcanic rocks in granite, sandstone or conglomerate in the ice, etc.

Tectonic processes and / or gravity can lead to the formation of caves whatever rock they occur (eg: lithostatic distension, collapses, subsidence etc.). Even in the cap or mountain glaciers, permanent ventilation, heat from hot springs or hot gases can create into ice caves with a unique dynamic.

Endokarstic Morphology

Karst morphology represents all landforms that are found in cavities underground, i.e. in caves and karst systems of which they are part.

Landforms are grouped into four categories, depending on the processes that generated them: precipitation, corrosion, erosion and detachment / crashing.

1. The forms of precipitation and deposition of calcium carbonate as calcite or aragonite form the generically called speleothems. Their diversity is reflected through shapes, sizes, site of generating, etc. The abundance and variety of speleothems gives a cave beauty, attractiveness and uniqueness, which are the defining issues that necessitate theirs preservation. Speleothems are formed from the precipitation of calcium carbonate (CaCO₃), accompanied by the release of carbon dioxide from solution. Thus, by recrystallization, arise a variety of shapes composed of mineral called calcite. Sometimes, under favorable conditions of temperature and pressure, calcium carbonate precipitated in the form of aragonite.

The most common types of speleothems are:

1. - Dripstone: Stalactites, Stalagmites, Columns
  - Flowstone: Draperies or curtains, Rimstone dams or gours, Stone waterfall formations simulate frozen cascades

Special forms of speleothems are:

- Cave crystals: Dogtooth spar, Frostwork, Moonmilk, Anthodites, Cryogenic calcite crystals,
- Speleogens like Pillars, Scallops, Boneyard, Boxwork
- and others like – Cave pearls, Cave popcorn, Snottites, Calcite rafts
The forms of corrosion result from the action of acidic water on limestone under certain conditions of temperature and pressure.
Limestone shows various forms of corrosion such as scallops: spoon-shaped hollows dissolved in cave walls, ceilings, and floors by flowing water.

The forms of erosion arise in galleries where water flows freely; their destructive action is enhanced by the transported material (mainly stones and sand) and which serves as carving tool for limestone. As the water speed is higher, so its erosive force increases. Thus, the forms of erosion can be observed especially in the floor and on the walls of galleries to where the water comes to floods.Giant’s kettles, also known as giant’s cauldrons or potholes, meander niches, excavations running, striations friction, columns, hulls, pillars and erosion levels are the most common forms of erosion in caves. Banquets and terraces – frequently encountered – are particular forms of erosion levels.
The forms of collapse or detachment
Besides speleothems in caves there are many forms of collapse – rock fragments of various sizes – as a result of the dynamic processes from underground. In general, water that infiltrates the existing cracks and causes them gradually widened the instability of rock fragments, collapsing. These rocks fracture and collapse in blocks of stone. In time, some may be covered by spectacular calcite formations. Others clog narrow passages and passing in this case is no longer possible.

References