The Death of Lake Bungunnia To understand in more detail how this aridification of Australia proceeded, we made innovative use of global positioning systems to obtain accurate elevation data for each locality where the sediments of Lake Bungunnia were found. These data reveal that the entire Blanchetown Clay is around 56 metres above sea level. The data also show that the Nampoo Member dust sediments are at around the same absolute elevation, providing evidence for their deposition at the same time across the whole of the basin.
The sediments of Lake Bungunnia include a thin sequence of carbonate called the Bungunnia Limestone. This type of sediment, however, is only found in the Morgan Sub-basin, the most western part of Lake Bungunnia in South Australia. Our elevation data show, for the first time, that these sediments are not continuous across the lake but are present on a series of terraces that range over more than 20 metres in elevation.
The terraces that we can recognise from the GPS and SRTM data show that lake levels decreased progressively through time, and that Lake Bungunnia began to shrink soon after the dust sediments were deposited within the Blanchetown Clay. The terraces themselves provide a unique record of the step-wise aridification of southern Australia — a bit like rings on a bath preserved as the lake system progressively dried up.
Importantly, the preservation of carbonate minerals such as dolomite, calcite and gypsum on these terraces shows that the climate continued to warm significantly after deposition of the Nampoo Member dust deposits. Environmental conditions in this period must have been similar to the modern Coorong Lagoon in South Australia where carbonate, rather than clay, is being deposited today.
Our work has also provided new constraints on the age of the lake using magnetostratigraphy. These data show that the oldest Blanchetown Clay, and therefore the formation of Lake Bungunnia, dates from around 2. The youngest Blanchetown Clay is probably around 1. The terraces on which we find Bungunnia Limestone are all lower in elevation than any of the Blanchetown Clay deposits, meaning that those sediments are younger still — probably as young as , or , years.
Positive IODs are associated with an increased chance for dry weather in southern and southeast Australia. The devastating Black Summer bushfires in —20 were linked to an extreme positive IOD, as well as human-caused climate change which exacerbated these conditions. Negative IODs tend to be less frequent and not as strong as positive IOD events, but can still bring severe climate conditions, such as heavy rainfall and flooding, to parts of Australia.
The IOD is determined by the differences in sea surface temperature on either side of the Indian Ocean. During a negative phase, waters in the eastern Indian Ocean near Indonesia are warmer than normal, and the western Indian Ocean near Africa are cooler than normal. This causes more moisture-filled air to flow towards Australia, favouring wind pattern changes in a way that promotes more rainfall to southern parts of Australia.
Generally, IOD events start in late autumn or winter, and can last until the end of spring — abruptly ending with the onset of the northern Australian monsoon. The negative IOD means the southern regions of Australia are likely to have a wet winter and spring.
Indeed, the seasonal outlook indicates above average rainfall for much of the country in the next three months. This belt pushes the air down instead of allowing the moisture-laden air from the surrounding oceans to rise and cause rainfall.
There are four seasons across most of Australia , with the tropical north experiencing a wet and dry season.
You might be interested: Which desert is located in the western part of australia. What makes Australia such a hostile country? The Sun — Australia lies under a hole in the ozone layer, and ultraviolet rays burn the skin like nothing else. Snakes — 21 of the 25 venomous snake species live in Australia. Sydney has been hit by its heaviest rain in 30 years, bringing widespread flooding but also putting out two massive bushfires in New South Wales.
Australia has warmed on average by 1. Iquique, Chile. Wadi Halfa, Sudan. Widespread deforestation has intensified flooding while also increasing the salinity of the soil so that the water flowing through it becomes brackish—unchecked this could damage millions of hectares of agricultural land.
The overgrazing of sheep and cattle, key economic exports, has been a major factor in desertification with vegetation loss leading to a loss of usable water. Until recently farmers were allowed to draw unchecked amounts of water from rivers causing silting, salination, and fierce disputes between competing users. Similarly, groundwater sources such as aquifers have been used up faster than they can be naturally replenished, especially in the arid interior, so that they are now having to be actively refilled with treated wastewater.
This is important because Australians consume liters of water per person per day. Of this, outdoor use is particularly heavy, accounting for nearly half of household consumption through car washing, hosing driveways, and using garden sprinklers at around 1, liters per hour. While many Australians are increasingly water aware, Sydney has cut its average daily use by liters per person since , further water savings will be vital to minimize future water stress. This brings the potential for significant water efficiencies through integrated infrastructure ranging from wastewater recycling to huge desalination plants.
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