Presuming that the term 'colonial Australia' refers to the first 100 years of the colonisation of Australia, the following events could be considered as significant:
1788 - Australia's first groups of white settlers, mostly convicts, arrived from England, along with officers, marines and free settlers. In the ensuing years, free settlers were encouraged to come, and the colony of New South Wales grew. Meanwhile, conflict between the traditional indigenous owners and the new white settlers increased, and the Aborigines began to decrease in number.
1801-1803 - Matthew Flinders circumnavigated Australia. This added considerably to the world maps of the time. Because of this journey, Flinders also recommended the name Terra Australis be adopted for the continent. In Governor Lachlan Macquarie's time, this became the name Australia.
1804 - A colony was established in Van Diemen's Land (now Tasmania)
1813 - Crossing of the Blue mountains by Blaxland, Lawson and Wentworth: they were the first Europeans to succeed in crossing Australia's impenetrable Blue Mountains, and allowing vital expansion of the settlement to the west. This was when Europeans stopped just clinging to the coastal areas of Australia, and instead began to really establish new settlements inland.
1824 The first colony (Colony of Moreton Bay) in what is now Queensland was established.
1829 The colony of Western Australia was officially proclaimed.
1829-30 Charles Sturt followed and charted the major rivers of New South Wales, opening up the waterways along the Murray and Darling Rivers, and generating interest in a southern colony (later South Australia).
1836 The colony of South Australia was proclaimed.
1840-41 Edward Eyre became the first European to travel overland from east to west, crossing the Nullarbor Plain in gruelling conditions, with just one aboriginal companion, after two other aborigines travelling with him killed his overseer.
1851 in April, gold prospector Edward Hargraves and his partners reported finding gold at Ophir NSW, beginning the Australian goldrush.
1851 Victoria separated from New South wales to become its own colony, and Australia's richest goldfields for the time were found in Victoria. The colony of Victoria grew exponentially, thanks to this discovery. The wealth brought by the discovery of gold was a significant catalyst to Australia eventually becoming a country made of states, not just a continent occupied by numerous colonies.
Nothing much. New South Wales was founded in 1788.
the break up of Pangaea
Reptiles evolved from amphibians
During the early years of Australia's colonial settlement, the English used Australia as a dumping ground for their unwanted convicts.
The massive and widespread Queensland floods occurred during the 2010-2011 Summer season in Australia.
The Rum Rebellion occurred in Sydney, New South Wales, during its early colonial years.
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Policemen were commonly called "troopers" in Australia during colonial times.
Policemen were commonly called "troopers" in Australia during colonial times.
The last major gold find in Australia was at Tennant Creek in the Northern Territory, and occurred during the 1930s.
Vatican I occurred during the 19th century, not 20th.
The discovery of the new world. The concept of the international law began.
Check out the related link. It list a majority of the events that occurred during 1974.