The Pinnacles are

limestone Limestone ( calcium carbonate ) is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of . Limestone forms whe ...

formations within

Nambung National Park Nambung National Park is a national park in the Wheatbelt region of Western Australia, 200 km northwest of Perth, Australia and 17 km south of the small coastal town of Cervantes. The park contains the Pinnacles Desert which is an are ...

, near the town of

Cervantes, Western Australia Cervantes is a town in Western Australia located off of Indian Ocean Drive about north-north-west of the state capital, Perth in the Shire of Dandaragan local government area. At the 2016 census, Cervantes had a population of 527. The town ...

Features

The area contains thousands of weathered limestone pillars. Some of the tallest pinnacles reach heights of up to 3.5m above the yellow sand base. The different types of formations include ones which are much taller than they are wide and resemble columnssuggesting the name of Pinnacleswhile others are only a meter or so in height and width resembling short tombstones. A cross-bedding structure can be observed in many pinnacles where the angle of deposited sand changed suddenly due to changes in prevailing winds during formation of the limestone beds. Pinnacles with tops similar to mushrooms are created when the

calcrete Caliche () is a sedimentary rock, a hardened natural cement of calcium carbonate that binds other materials—such as gravel, sand, clay, and silt. It occurs worldwide, in aridisol and mollisol soil orders—generally in arid or semiarid regions, ...

capping is harder than the limestone layer below it. The relatively softer lower layers weather and erode at a faster rate than the top layer leaving behind more material at the top of the pinnacle.Pinnacles Desert Lookout and Drive
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Formation

The raw material for the limestone of the Pinnacles came from

seashell A seashell or sea shell, also known simply as a shell, is a hard, protective outer layer usually created by an animal or organism that lives in the sea. The shell is part of the body of the animal. Empty seashells are often found washe ...

s in an earlier era that was rich in

marine life Marine life, sea life, or ocean life is the plants, animals and other organisms that live in the salt water of seas or oceans, or the brackish water of coastal estuaries. At a fundamental level, marine life affects the nature of the planet. M ...

. These shells were broken down into lime-rich

sand Sand is a granular material composed of finely divided mineral particles. Sand has various compositions but is defined by its grain size. Sand grains are smaller than gravel and coarser than silt. Sand can also refer to a textural class of s ...

s that were blown inland to form high mobile

dune A dune is a landform composed of wind- or water-driven sand. It typically takes the form of a mound, ridge, or hill. An area with dunes is called a dune system or a dune complex. A large dune complex is called a dune field, while broad, f ...

s.Lipar, M., Webb, J.A., 2015. The formation of the pinnacle karst in Pleistocene aeolian calcarenites (Tamala Limestone) in southwestern Australia. Earth-Science Reviews 140, pp. 182-202 However, the manner in which such raw materials formed the Pinnacles is the subject of debate. Three major theories have been proposed: The first theory states that they were formed as dissolutional remnants of the

Tamala Limestone Tamala Limestone is the geological name given to the widely occurring eolianite limestone deposits on the western coastline of Western Australia, between Shark Bay in the north and nearly to Albany in the south. The rock consists of calcarenit ...

, i.e. that they formed as a result of a period of extensive solutional weathering (

karstification Karst is a topography formed from the dissolution of soluble rocks such as limestone, dolomite, and gypsum. It is characterized by underground drainage systems with sinkholes and caves. It has also been documented for more weathering-resistant ro ...

). Focused solution initially formed small solutional depressions, mainly solution pipes, which were progressively enlarged over time, resulting in the pinnacle topography. Some pinnacles represent cemented void infills (

microbialites Microbialite is a benthic sedimentary deposit made of carbonate mud (particle diameter < 5 μm) that is formed with the mediation of microbes. The constituent carbonate mud is a type of

erosion Erosion is the action of surface processes (such as water flow or wind) that removes soil, rock, or dissolved material from one location on the Earth's crust, and then transports it to another location where it is deposited. Erosion is distin ...

, but dissolution still played the final role in pinnacle development.Lipar, M., 2009. Pinnacle syngenetic karst in Nambung National Park, Western Australia. Acta Carsologica 38 (1), pp. 41–50. A second theory states that they were formed through the preservation of

tree In botany, a tree is a perennial plant with an elongated stem, or trunk, usually supporting branches and leaves. In some usages, the definition of a tree may be narrower, including only woody plants with secondary growth, plants that are ...

casts buried in coastal aeolianites, where roots became groundwater conduits, resulting in the precipitation of

indurated Friability ( ), the condition of being friable, describes the tendency of a solid substance to break into smaller pieces under duress or contact, especially by rubbing. The opposite of friable is indurate. Substances that are designated hazardous, ...

(hard)

. Subsequent wind erosion of the aeolianite then exposed the calcrete pillars.Hearty, P.J., O’Leary, M.J., 2008. Carbonate eolianites, quartz sands, and Quaternary sea-level cycles, Western Australia, A chronostratigraphic approach. Quaternary Geochronology 3, 26-55 A third proposal suggests that

plants Plants are predominantly Photosynthesis, photosynthetic eukaryotes of the Kingdom (biology), kingdom Plantae. Historically, the plant kingdom encompassed all living things that were not animals, and included algae and fungi; however, all curr ...

played an active role in the creation of the Pinnacles, based on the mechanism that formed smaller "root casts" in other parts of the world. As

transpiration Transpiration is the process of water movement through a plant and its evaporation from aerial parts, such as leaves, stems and flowers. Water is necessary for plants but only a small amount of water taken up by the roots is used for growth a ...

drew water through the soil to the roots, nutrients and other dissolved minerals flowed toward the root—a process termed "mass-flow" that can result in the accumulation of nutrients at the surface of the root, if the nutrients arrive in quantities greater than that needed for plant growth. In coastal aeolian sands that consist of large amounts of calcium (derived from marine shells), the movement of water to the roots would drive the flow of calcium to the root surface. This calcium accumulates at high concentrations around the roots and over time is converted into a calcrete. When the roots die, the space occupied by the root is subsequently also filled with a carbonate material derived from the calcium in the former tissue of the roots, and possibly also from water leaching through the structures. Although evidence has been provided for this mechanism in the formation of root casts in

South Africa South Africa, officially the Republic of South Africa (RSA), is the southernmost country in Africa. It is bounded to the south by of coastline that stretch along the South Atlantic and Indian Oceans; to the north by the neighbouring countri ...

, evidence is still required for its role in the formation of the Pinnacles.Cramer MD, Hawkins H-J. 2009. A physiological mechanism for the formation of root casts. Palaeogeography, Palaeoclimatology, Palaeoecology 274: 125–133

Fauna and flora

Western grey kangaroo The western grey kangaroo (''Macropus fuliginosus''), also referred to as a western grey giant kangaroo, black-faced kangaroo, mallee kangaroo, sooty kangaroo and (when referring to the Kangaroo Island subspecies) Kangaroo Island grey kangaroo, is ...

s graze on the vegetation in the park, usually in the early morning. The kangaroos are considered quite tame, sometimes allowing quiet, slow-moving visitors to approach them.

Baudin's black cockatoo Baudin's black cockatoo (''Zanda baudinii''), also known as Baudin's cockatoo or the long-billed black cockatoo, is a species of genus '' Zanda'' found in southwest Australia. The epithet commemorates the French explorer Nicolas Baudin. It has ...

s and

emu The emu () (''Dromaius novaehollandiae'') is the second-tallest living bird after its ratite relative the ostrich. It is endemic to Australia where it is the largest native bird and the only extant member of the genus ''Dromaius''. The emu' ...

s are frequently observed in the park. Reptiles such as bobtails,

sand goanna The sand goanna (''Varanus gouldii'') is a species of large Australian monitor lizard, also known as Gould's monitor, sand monitor, or racehorse goanna. Taxonomy John Edward Gray described the species in 1838 as ''Hydrosaurus gouldii'', noting ...

s and carpet pythons are a few of the other park inhabitants. Some of the common plant species include panjang (a low-lying wattle), coastal wattle and banjine,

quandong Quandong, quandang or quondong, is a common name for the species '' Santalum acuminatum'' (desert, sweet, Western quandong), especially its edible fruit, but may also refer to * '' Aceratium concinnum'' (highroot quandong) * '' Peripentadenia mea ...

, yellow tailflower, thick-leaved fanflower and cockies tongues.

Parrot bush ''Banksia sessilis'', commonly known as parrot bush, is a species of shrub or tree in the plant genus ''Banksia'' of the family Proteaceae. It had been known as ''Dryandra sessilis'' until 2007, when the genus '' Dryandra'' was sunk into ''Bank ...

, candlestick banksia, firewood banksia and acorn banksia are also common in the park.

Tourism

The Pinnacles remained unknown to most Australians until 1967 when the area was gazetted as a reserve, which was later combined with two adjacent reserves to form

in 1994. Nambung National Park received about 150,000 visitors a year as of 2011. The Pinnacles Desert Discovery Centre was opened in 2008, offering interpretive displays of the park, both the natural processes that formed the Pinnacles and the biodiversity of the area. The best season to visit the Pinnacles is in the months of August to October, as the days are mild and wildflowers, along with wattle, begin to bloom in the spring. No lodging or camping areas are available within Nambung National Park but accommodations can be found in Cervantes. Pinnacle3

References

External links