Lynch's Crater () formed about 230,000 years ago during an explosive volcanic eruption, creating a

maar A maar is a broad, low-relief volcanic crater caused by a phreatomagmatic eruption (an explosion which occurs when groundwater comes into contact with hot lava or magma). A maar characteristically fills with water to form a relatively shallow ...

on the eastern edge of the

Atherton Tableland The Atherton Tableland is a fertile plateau, which is part of the Great Dividing Range in Queensland, Australia. It has very deep, rich basaltic soils and the main industry is agriculture. The principal river flowing across the plateau is the B ...

Queensland Queensland ( , commonly abbreviated as Qld) is a States and territories of Australia, state in northeastern Australia, and is the second-largest and third-most populous state in Australia. It is bordered by the Northern Territory, South Austr ...

Australia Australia, officially the Commonwealth of Australia, is a country comprising mainland Australia, the mainland of the Australia (continent), Australian continent, the island of Tasmania and list of islands of Australia, numerous smaller isl ...

. Located at an altitude of about 760 m, the crater is about 80 m deep and has been heavily worn by erosion. Following its formation, a crater lake formed in the depression that was gradually filled in with deposits, so that the surface is now an average of 45 m beneath the rim. The present day interior is filled with swampy ground that is maintained by a stream flowing in from the eastern side. This water exits the crater to form a tributary of the

North Johnstone River The Johnstone River, comprising the North Johnstone River and the South Johnstone River, is a river system in Far North and North Queensland, Australia. The headwaters of the river system rise in the Atherton Tablelands. The north branch o ...

. The mean annual rainfall at this site is 2,500 mm. Sedimentary deposits in the crater provide pollen samples covering most of the last 200,000 years of vegetation growth in the region; spanning the last two

glacial period A glacial period (alternatively glacial or glaciation) is an interval of time (thousands of years) within an ice age that is marked by colder temperatures and glacier advances. Interglacials, on the other hand, are periods of warmer climate betw ...

s. During the interglacial epochs, the crater was occupied by mesic

evergreen In botany, an evergreen is a plant which has Leaf, foliage that remains green and functional throughout the year. This contrasts with deciduous plants, which lose their foliage completely during the winter or dry season. Consisting of many diffe ...

rainforest Rainforests are forests characterized by a closed and continuous tree Canopy (biology), canopy, moisture-dependent vegetation, the presence of epiphytes and lianas and the absence of wildfire. Rainforests can be generally classified as tropi ...

. In the cooler glacial periods, this was replaced by rain forests prevalent in drier climes. From 40,000 years ago, the crater was gradually occupied by

sclerophyll Sclerophyll is a type of vegetation that is adapted to long periods of dryness and heat. The plants feature hard leaves, short Internode (botany), internodes (the distance between leaves along the stem) and leaf orientation which is parallel or ...

vegetation such as ''

Casuarina ''Casuarina'', also known as she-oak, Australian pine and native pine, is a genus of flowering plants in the family Casuarinaceae, and is native to Australia, the Indian subcontinent, Southeast Asia, islands of the western Pacific Ocean, and e ...

'' and ''

Eucalyptus ''Eucalyptus'' () is a genus of more than 700 species of flowering plants in the family Myrtaceae. Most species of ''Eucalyptus'' are trees, often Mallee (habit), mallees, and a few are shrubs. Along with several other genera in the tribe Eucalyp ...

'', with the transition being completed 26,000 years ago. Around 10,000 years ago, evergreen vegetation once more regained dominance. Particles of charcoal dated from up to 38,000 years ago are believed to be the result of fires lit by

Aboriginal Australians Aboriginal Australians are the various indigenous peoples of the Mainland Australia, Australian mainland and many of its islands, excluding the ethnically distinct people of the Torres Strait Islands. Humans first migrated to Australia (co ...

, and are coincident with the appearance of the sclerophyll vegetation and loss of regional

megafauna In zoology, megafauna (from Ancient Greek, Greek μέγας ''megas'' "large" and Neo-Latin ''fauna'' "animal life") are large animals. The precise definition of the term varies widely, though a common threshold is approximately , this lower en ...

References

{{Reflist, refs= {{Citation , first1 = A. P. , last1 = Kershaw , title = A Late Pleistocene and Holocene Pollen Diagram from Lynch's Crater, North-Eastern Queensland, Australia , journal = New Phytologist , pages = 469–498 , volume = 77 , issue = 2 , year = 1976 , jstor=2433618 , postscript= . , doi=10.1111/j.1469-8137.1976.tb01534.x , doi-access= free {{Citation , first1 = Uwe , last1 = Rieser , first2 = Raphael A. J. , last2 = Wüst , title = OSL chronology of Lynch's Crater, the longest terrestrial record in NE-Australia , journal = Quaternary Geochronology , pages = 233–236 , volume = 5 , issue = 2–3 , date=April–June 2010 , doi = 10.1016/j.quageo.2009.05.014 , postscript= . {{Citation , first1 = Jeremy , last1 = Russell-Smith , first2 = Peter , last2 = Stanton , editor1-first = Ross Andrew , editor1-last = Bradstock , editor2-first = Jann Elizabeth , editor2-last = Williams , editor3-first = Arthur Malcolm , editor3-last = Gill , chapter = Fire regimes and fire management of rainforest communities , title = Flammable Australia: The Fire Regimes and Biodiversity of a Continent , publisher = Cambridge University Press , page = 333 , year = 2002 , isbn = 0521805910 , chapter-url = https://books.google.com/books?id=4f8anIoS33MC&pg=PA333 , postscript= . {{Cite journal , last1 = Rieser , first1 = Uwe , last2 = Wüst , first2 = Raphael A.J. , title = OSL chronology of Lynch's Crater, the longest terrestrial record in NE-Australia , journal = Quaternary Geochronology , volume = 5 , issue = 2–3 , pages = 233–236 , year = 2010 , doi = 10.1016/j.quageo.2009.05.014 Maars of Australia Landforms of Far North Queensland