Editing Nullarbor Plain (section)

==Geology and geography==
[[Image:Nullarbor Plain Escarpment DSC04558.JPG|thumb|right|A road sign displaying the distance from Eucla and [[Ceduna, South Australia|Ceduna]]
(Regarding the information on the road sign, this stretch of the [[Eyre Highway]] lies not in the Nullarbor Plain, but south of the plain, in the [[Hampton bioregion]] of [[Western Australia]], on the [[Roe Plains]], somewhere around Mundrabilla. The Nullarbor Plain stretches behind the hills or, rather, the [[Hampton Tableland]], seen in the background) ]]
The Nullarbor Plain is a former shallow [[seabed]], as indicated by the presence of [[bryozoa]]ns, [[foraminifera]], [[echinoid]]s and [[red algae]] calcareous skeletons that make up the [[limestone]].<ref name="Webb">{{cite book |author=John A. Webb & Julia M. James |year=2006 |chapter-url=http://www.latrobe.edu.au/geosci/Downloads/pdfs/John%20Webb_Jan%2009/Geomorphology/Webb%20&%20James%202006.pdf |chapter=Karst evolution of the Nullarbor Plain, Australia |editor=Russell S. Harmon & Carol M. Wicks |title=Perspectives on Karst Geomorphology, Hydrology and Geochemistry – a Tribute Volume to Derek C. Ford and William B. White |publisher=[[Geological Society of America]] Special Paper 404 |pages=65–78 |isbn=978-0-8137-2404-1 |doi=10.1130/2006.2404(07)}}</ref> The region is also the location of "Nullarbor limestone" and it has a reputation as a significant [[karst]] region<ref name="Lipar">Lipar, M., Ferk, M., (2015). Karst pocket valleys and their implications on Pliocene-Quaternary hydrology and climate: examples from the Nullarbor Plain, southern Australia. Earth-Science Reviews 150, pp. 1–13.</ref> with [[Oligocene]] and [[Miocene]] cave formations.<ref name="Webb"/><ref>{{Cite web|url=https://asud.ga.gov.au/search-stratigraphic-units/results/25355|title=Australian Stratigraphic Units Database, Geoscience Australia|website=asud.ga.gov.au|access-date=15 September 2019}}</ref>

The sequence within the limestone includes five formations:
*the upper formation is the Nullarbor Limestone which is early middle [[Miocene]] in age;
*the Mullamullang member of this formation is a [[Unconformity|paraconforming]] member, being separated by 5 million years;<ref name="Webb"/>
*the third member is the Abrakurrie Limestone that was formed in a central depression of the earlier formation; this is late [[Oligocene]] to Early Miocene in age and does not reach the edge of the plain;<ref name="Webb"/>
*the last two formations are [[conforming]] formations; the late [[Eocene]] Toolinna Limestone lies on the Wilsons Bluff Limestone which is mid- to late Eocene in age; and
*the Toolinna Limestone does not cover the whole Nullarbor and is extant only in the extreme east beside the Abrakurrie formation which lies in a depression.
One theory is that the whole area was uplifted by crustal movements in the Miocene, and since then, [[erosion]] by wind and rain has reduced its thickness. The plain has most likely never had any major defining [[topography|topographic]] features, resulting in the extremely flat terrain across the plain today.<ref name="Webb"/>

According to Curtin University research published in 2023, "Nullarbor drastically shifted to dry conditions between 2.4 and 2.7 million years ago".<ref>[https://www.sciencedaily.com/releases/2023/04/230418101414.htm Nullarbor rocks reveal Australia's transformation from lush to dust]. sciencedaily.com April 18, 2023</ref>

In areas, the southern ocean blows through many caves, resulting in [[blowhole (geology)|blowhole]]s up to several hundred metres from the coast. The [[Murrawijinie Cave]] in South Australia is open to the public, but most of the Nullarbor Caves on the Western Australian side can only be visited and viewed with a permit from the [[Department of Environment and Conservation (Western Australia)|Department of Parks and Wildlife]].<ref>{{Cite web|url=https://parks.dpaw.wa.gov.au/know/adventure-activities|title=Adventure Activities &#124; Explore Parks WA &#124; Parks and Wildlife Service|access-date=15 September 2019}}</ref><ref>{{cite web|url=https://parks.dpaw.wa.gov.au/sites/default/files/downloads/know/Lawful%20authority%20to%20access%20nullarbor%20caves.docx|title=Application for Lawful Authority to Access Nullarbor Caves|publisher=Department of Parks and Wildlife|access-date=13 May 2021}}</ref>

The Nullarbor is known for extensive [[meteorite]] deposits, which are extremely well preserved in the arid climate. In particular, many meteorites have been discovered around [[Mundrabilla, Western Australia|Mundrabilla]], some up to several [[tonne]]s in weight.<ref>{{Cite web|url=https://www.lpi.usra.edu/meteor/docs/mb77.html|title=The Meteoritical Bulletin, No. 77, 1994 November|website=www.lpi.usra.edu|access-date=15 September 2019}}</ref>

According to the [[USDA soil taxonomy]] system, the Nullarbor's soils are classified as mainly consisting of [[aridisol]]s.<ref>{{cite web|url=http://soils.usda.gov/use/worldsoils/mapindex/order.html|title=Global Soil Regions|publisher=United States Department of Agriculture|date=November 2005|access-date=14 September 2013}}</ref>

=== Limits ===
[[Image:Highway sign, Nullarbor, 2017 (02).jpg|thumb|Sign defining the edge of the plain at the western side. (This photograph depicts Nullarbor Roadhouse, seen from the west. Nullarbor Roadhouse lies on the South Australian side of the Eyre Highway, at the eastern edge of the Nullarbor Plain as well as [[Nullarbor National Park]], which both extend miles farther west into Western Australian territory.)]]
Frequently ''The Nullarbor'' is expanded in tourist literature and web-based material to loosely refer to all the land between [[Adelaide]], [[South Australia]] and [[Perth]], [[Western Australia]]. Through observing satellite images, the limits of the limestone formation of the plain can be seen to stretch from approximately {{Cvt|20|km}} west of the original Balladonia settlement (now abandoned) to its easternmost limit a few kilometres west of the town of Ceduna.<ref>''A tourist map of the Nullarbor Plain Perth to Adelaide'' Scale 1:2,250,000 (E 116°00' --E 139°00'/S 30°00'--S 38°00') Unley, S. Aust. : Carto Graphics, {{ISBN|0-9579060-4-8}}</ref>