Caves

Every year there are reported exciting discoveries of new caves and discoveries of new qualities such as cave paintings in the ones known before. But there still is a feeling that our knowledge covers just a small part of all these monuments of nature.

Though, those which we know offer a surprising diversity of unusual features and impressive sights.

Definition

Cave is natural underground space which is large enough for human to enter.

As a separate subcategory there are included also sinkholes – large natural depressions or holes, which for most part represent collapsed caves.

Criteria

Category includes caves with outstanding characteristics such as large size, significant geological, biological or archaeological values.

Formation

Fairly solid rock is required to have rigid cave walls and ceilings. Several geologic processes can create large hollows in such solid rock. Most common ones are:

• Dissolution – hollows are created by the flow of water (in most cases) or gases. The process of the solution is facilitated by the naturally occurring acids in groundwater. This is the most frequent cave formation process which for the most part takes place in limestone, dolomite, marble, gypsum and other comparatively easily soluble rocks. Dissolved minerals in hollows form diverse interesting speleothems – stalactites, stalagmites, columns and also beautiful crystals. Countless caves have beautiful stalactite and stalagmite formations and many show caves are marketed as being the most beautiful ones. Wondermondo will not judge which is the most beautiful one but few will object that Lechuguilla Cave (New Mexico, United States), Phong Nha cave (North Central Coast, Vietnam) or Kap Kutan cave (Lebap, Turkmenistan) are gorgeous. If there is enough time, water can dissolve even quartzite – material considered to be insoluble. The longest known quartzite cave is the 16 kilometres long System Roraima Sur (Bolivar, Venezuela).
• Volcanic proccesses form several kinds of so-called primary caves – caves which form together with the surrounding rock. Lava tubes are created in conditions where hot lava stream gets a harder crust which remains after the lava flows away. Sounds impossible but such process have created even such cave as Kazumura Cave (Hawaii, United States) which is 65.5 kilometers long!
• Erosion processes of the sea waves and streams, but sometimes even wind, often create short caves. Sea caves often have beautiful lighting – only blue rays of the sunlight remain after going through the layer of seawater (Blue Grotto in Capri, Italy).

Many caves are formed otherwise – by glacial processes, earthquakes, biological processes – even by elephants (Kitum Cave in Kenya).

Values

Caves can be unique in several ways: most often due to their geological, biological and archaeological values.

Geological values

Many caves are adorned with diverse speleothems – specific rock and mineral formations seen only in caves and created by mineral solutions sedimenting the dissolved minerals in cave. Diversity of speleothems is very high and from time to time there are discovered new fantastic forms. Most common speleothems are stalactites, stalagmites, columns and flowstones. Sometimes such speleothems can reach incredible size: the tallest stalagmites can reach 70 metre height (Zhijin Cave in Guizhou, China).

There are also very exotic and rare speleothems such as:

• Cave pearls – limestone balls up to 15 centimeters in diameter. The floor of Gruta de las Canicas (Tabasco, Mexico) is covered with some 200,000,000 cave pearls! Cave pearls are beautiful – sparkling white or with a marble texture.
• Cave ballons – real ballons from minerals! Ballon is made of hydromagnesite and moonmilk (fine, white pasta of carbonate material) and filled with gas.
• Cave showerheads – hollow cones attached to the ceiling of the cave with the narrow end. As if to justify its name one such showerhead in Deer Cave (Sarawak, Malaysia) is the source of shower – waterfall.
• "Champignons" – opal formations of microbial origin in quartzite caves (Venezuela). These weird formations are up to 1 metre across. Quartzite caves in tepuis of Venezuela are known to have several kinds of otherworldly formations, weird symbiosis of minerals and microorganisms.

Cave environment is very beneficial for the formation of crystals. The largest crystals ever found are up to 12 metres long and 55 tons heavy, beautiful translucent crystals of gypsum in the Cave of the Crystals (Chihuahua, Mexico). Often crystals in caves form very beautiful and unusual formations such as white, intricate "trees" of aragonite crystals or gypsum flowers.

Caves have lots of other interesting geological characteristics such as unique minerals, for example sveite is found in Autana Cave (Venezuela), archerite is found only in caves where are bat guano deposits.

Biological values

The specific cave environment provides shelter for certain species adjusted for more or less permanent life in cave. Scientists have specific names for several groups of cave dwellers:

• Trogloxenes use caves but they need to leave caves periodically to survive, e.g. to get food. Typical trogloxenes are bats. Bracken Bat Cave (Texas, United States) with some 20 million bats is considered to have the largest bat colony of the world.
• Troglophiles are attracted by the caves due to cave environment, but survive in other conditions as well. Famous troglophile is New Zealand glow-worm (Arachnocampa luminosa). Larvae of this small insect attach at the ceiling and walls of many caves and emit blue-green light. This creates unforgettable sights in such caves as Waitomo Glowworm Cave (Waikato, New Zealand).
• Troglobites – animals living only in caves and fully dependant on cave environment. This is very specific group of animals well adapted to a life in total darkness, limited food supply and narrow space. If animal is living in cave waterbodies, he could be called also stygobite.

Troglobites are unique organisms adapted to specific life conditions and high isolation. Cave dwellers can be slow and live very long lives – up to 175 years, they often do not have eyes but other senses are heightened. Hundreds of species of troglobites are found only in one cave and not anywhere else. So far there are known approximately 7,700 species of troglobites but further investigations could increase this number several times.

The largest known troglobite is Black Proteus (Proteus anguinus parkelj) living in few caves of Slovenia. It is up to 35 centimeters long.

The highest cave biological diversity is observed not in tropical regions but in Europe. Most biodiverse is Sistema Postjna-Planina (Notranjsko-kraška, Slovenia) with 84 species of cave dwellers. A unique monument of nature is Movile Cave (Constanţa County, Romania) with 33 species of animals found only in this cave.

Microorganisms in some caves and also sinkholes create unique conditions. Thus the highly unusual Black Hole of Andros (South Andros, Bahamas) is water-filled sinkhole where at the depth of 18 meters is a dark purple layer of toxic sulfur bacteria. In this layer of bacteria due to biochemical processes, the water temperature increases up to 36°C. In Venezuelan quartzite caves, microorganisms create unusual opal formations – dendrites, "Champignons" and also unusual stalactites.

During the ice age several species of large animals in Europe and the Americas found that caves provide suitable habitat in harsh climatic conditions. Developed such species and subspecies of large animals as cave bear (Ursus spelaeus), cave hyena (Crocuta crocuta spelaea), Balearic cave goat (Myotragus balearicus). Evidence of these and many other extinct animals is found in many caves around the world, notably Peştera Urşilor (Bihor County, Romania) with remains of some 140 cave bears.

Archaeological values

The history of the development of humans has been well preserved in the caves of the world. Sterkfontein Caves (Gauteng, South Africa) contain remains of some 500 early hominins up to 3.3 million years old. Caves contain remnants of extinct human species such as Neanderthals (Homo neanderthalensis) whose last refuge seems to be the southern Iberian peninsula. Here in Gorham’s cave (Gibraltar) have been found the most recent known, around 30,000 – 24,500 years old remnants of Neanderthals.

Most recent another species of human have been found in Liang Bua cave (Flores, Indonesia). This man, Homo floresiensis, went extinct some 12,000 years ago.

Caves contain valuable artwork of prehistoric man such as the oldest known artwork – 70,000 years old engraved pieces of ochre (Blombos cave in Western Cape, South Africa) and the oldest sculpture in the world – 35 – 40 thousand years old "Venus of Hohle Fels" (Hohle Fels in Baden-Württemberg, Germany). Petroglyphs of Bhimbetka Caves (Madhya Pradesh, India) might be even 290 – 700 thousand years old.

Conditions in caves are beneficial for preserving artwork and there are known many hundreds of caves with prehistoric paintings in the whole world. Many cave paintings show that tens of thousands of years ago inspiration and skills of artists did not differ too much from that of contemporary artists.

The oldest known cave art comes from Fumane Cave (Veneto, Italy) where barely discernible drawings on the pieces of rocks are some 32,000 – 36,500 years old. Chauvet Cave (Ardèche, France) has 30,000 – 33,000 years old drawings and here the quality of artwork is already very high. Some of the best monuments of cave art in the world are in Cave of Altamira (Cantabria, Spain) and Lascaux (Dordogne, France). Unusual and well matured artistic style is represented in Laas Gaal (Togdheer Region, Somalia). Great 9,000 years old stencil art is represented in Cueva de los Manos (Santa Cruz, Argentina), even more impressive stencils were made by ancient Aborigenes in Cathedral Cave (Queensland, Australia). Unusual are the 6,000 – 8,000 years old pictograms in Edakkal Caves (Kerala, India).

Numerous important archaeological finds have been made in Central American caves. Sometimes around 1,200 – 900 BC have been made Olmec influenced paintings in Juxtlahuaca (Guerrero, Mexico). Maya culture has left important artefacts in sacred wells (cenotes) such as the Sacred Cenote (Yucatán, Mexico). Naj Tunich (Peten, Guatemala) – former Mayan ceremonial cave – contains diverse important artefacts: petroglyphs, paintings, ceramics, burials.

Hidden and fragile

Caves in a way are "hidden monuments" because nearly any cave contains very fragile values which are easily lost through unorganised tourism and vandalism.

We can be sure that in every single country, where are found caves, local speleologists (cave explorers) know a huge lot more than is written in tourist guidebooks. But we should not complain about this: unfortunately there is no other way to preserve cave art, fragile crystals and unique, delicate animals living in caves. It feels much better to know that they exist somewhere than to experience a loss of values due to the faulty nature of human.