Great Australian Desert explained 1080p

The land down under is best known for its vast and remote outback covering most of the country's interior, while in reality it is covering climatic zones ranging from tropical to temperate. It is best known for its arid centre where the most extreme landscapes of Australia are forming a mosaic of salt and red earths, collectively called the Great Australian Desert. What may seem like a whole lot of nothingness is actually a continent-sized system that runs on brief violent ancient aquifers moving in million-year cycles and explosions of colours where you would least expect them. To better understand this enormous system, in this video we'll first get some general context on the most arid parts of Australia before traversing half the continent to see how these deserts actually work. Chapter 1. Origins of the Australian Desert First of all, we need to clear up some misconceptions of the Great Australian Desert. When searching for a list of the largest deserts by area, the so-called Great Australian Desert often takes the fifth spot after the Poles, the Sahara and the Arabian Desert. But this isn't entirely correct. Geographically speaking, there isn't really a single entity called the Great Australian Desert, but instead a collection of ten deserts that follow the framework and limits of the Interim Biogeographic Regionalization for Australia that informally make up the Great Australian Desert. These ten deserts are largely organized into an eastern and western cluster, but while I have drawn clear borders between the constituents here, they are a little bit more fuzzy in reality. Deserts are commonly defined not by heat but by the water balance, and with the rule of thumb that any area receiving less than 250 mm of rain per year is considered a desert. This rule, however, doesn't capture many edge cases, so the concept of an aridity index is sometimes used instead. That index is simply rainfall divided by the atmosphere's drying power, meaning how much water could evaporate given temperature, sun, humidity and wind, and in deserts this index is typically below 0.2. In the case of our Australian Desert, these criteria are always met in the core of each desert, but become less precise around the margins. Further, unlike deserts like the Sahara or Arabian Desert, the Australian Desert can be a lot more erratic. Sudden cloudbursts can exceed the precipitation threshold in a single day, while other years see no precipitation at all. The transition zones from one desert to another are also not as precise as I have drawn them here. Instead, it is an approximation aggregating various different sources that use dominant landforms, vegetation and drainage patterns to distinguish between the deserts. Besides the where, we should also clarify the why, since many other regions in the world at the same latitude are covered in lush forests. The foremost reason for aridity in Australia's heart is its general position on the globe. Placed between 25 and 35 degrees latitude, the Australian deserts lie right below the Global High Pressure Zone around the tropics of Capricorn. Warm air over the equator expels most of its moisture as it rises and cools down before travelling southwards. As the air sinks again over the subtropical ridge, the warming air loses relative humidity, leading to dry air arriving over the Australian continent. Further, the West Australian Current, as part of the Antarctic Circulation, brings cold waters to Australia's western coast, preventing any significant evaporation from collecting in the coastal regions. On the east, the Great Dividing Range enhances rainfall on the coastal side and can reduce moisture penetration inland, contributing to a sharp wet-dry gradient across the continent. The combination of all of these factors make the continent of Australia the second driest continent on the planet after the Antarctic Ice Desert. But within these harsh conditions also lie a lot of geographical peculiarities, which we will travel through from west to east, bringing us to Chapter 2. The Western Desert Starting just behind the coast of the Dhampir land lies the Great Sandy Desert, the first of 5 deserts in this larger cluster. Right off the bat, it boasts some of the highest temperatures of Australia, which pushes against the slightly higher precipitation than what you would typically see in the desert. The average of 300mm of rain that falls annually can be misleading though, since this region is known for some of the most erratic weather. The most extreme region in the north experiences 30-40 localised thunderstorms annually, yet some storms drop little or no measurable rain at the surface, since the hot climate evaporates any moisture before it reaches the ground in a process called virga. The weather is not just erratic on an annual basis though, and decade-long shifts can completely transform entire regions. Looking at the weather station at Territory Grape Farm in the Northern Territory for example, in 1925 precipitation measurements yielded 25mm of annual rain, while in 1974 this figure skyrocketed to 955mm, just to average back down to 310mm since the 1990s. When the water does make it through though, it can often lead to flash floods that submerge the interdune corridors in a blanket of water, kicking off an incredible but short-lived circle of life. Dormant seeds are shooting out of the ground to form wildflower fields while insect populations explode and birds start breeding. Water collects in dozens of small drainage basins across the western desert, just to disappear again a few days or weeks after the most severe rainfall, leading to the flora and fauna slipping back into dormancy. Where the dune seas give way to vegetation, hammergrasses are among the few plants tough enough to hold on, but in parts of the Great Victoria Desert even that disappears. This region of Australia is one of the most tectonically stable, meaning that eroding forces like wind and water had a lot of time to act upon the same surfaces. While it is not particularly windy in the Great Victorian Desert, consistency does the job as well, so in certain areas nearly all fine material has been stripped away, leaving nothing but virtually never-ending pebble fields. These formations are called desert pavement, or gibber fields, and while scientists still debate the details of how fast they form and which processes dominate in different places, it is clear why vegetation has a hard time growing here. Another habitat that is almost devoid of life are the hundreds of ephemeral lakes scattered around the western desert. Being filled by the short bursts of rain, most of these lakes are dried for most of the year, exposing their reflective salt pans and organic residue that is left after evaporation. The largest of these lake basins can cover hundreds of kilometres in width and length, though the concept of shoreline is a bit arbitrary here. The salt crusts and sediment deposits have flattened out the basin to such an extent that a few centimetres of water can create water coverage of hundreds of square kilometres, and satellite imagery can be quite misleading in trying to identify water coverage. Clay-rich surfaces can look dark and wet, despite the absence of water, and pools of white salt beds can imitate a dry surface while they're actually submerged. These mirage-forming nature spectacles are not limited to the western deserts though. As we cross a semi-arid corridor of plains and mountains to the east, we are once again greeted by something even stranger. Before we step into the vast landscape of the ephemeral streams and enormous ancient aquifers though, let's take a step back and zoom out for a bit. The Australian deserts we've seen so far are only a small fraction of the earth's dryland, and if you want to test how well you can actually place these deserts on a map, the sponsor of this video, Yordglobe Geography, has what you're looking for. You can play countless game modes where your knowledge of countries, cities, flags, mountain ranges, islands and deserts are tested. I've been especially enjoying the daily challenges, which combine history and and the dual mode, where you can challenge friends and online users in a global battle of general knowledge. If you want to challenge me for a game, just send a game invite to Factspark, or follow the link in the description below. Yordglobe Geography is one of the best ways to study all the intricacies of geography, so if you want a more interactive way to deepen the knowledge on the topics that we're already discussing on this channel, download Yordglobe Geography for free on Google Play and the App Store. I'll leave the link in the description below, and now let's continue with the second half of the Great Australian Deserts. Chapter 3 – The Eastern Deserts Separated by a series of semi-arid ecoregions like the Stony Plains, Finca, Macdonald Ranges and the Bird Plains to the east, a cluster of five more deserts are covering the centermost outback. The storm-driven, boom-bust ecosystems of dunes and gibber fields now transition to a somewhat calmer ecosystem that is shaped by large ephemeral rivers and the largest aquifer on the planet. Spanning 1.7 million square kilometers, roughly the size of Alaska or countries like Mongolia or Iran, the Great Artesian Basin underlies 22% of Australia and is a vital lifeline for the continent. Alternating layers of porous sandstone and watertight shale or mudstone are forming lens-shaped balls reaching from the Great Dividing Range to the heart of the outback, trapping groundwater in million-year-long cycles. From the highest elevations of New South Wales, the aquifer reaches up to 3,000 meters into the ground, and water which enters the exposed porous layers in the mountains can take up to 2 million years until it reaches the westernmost extent under the desert. Here, natural springs and seeps, cracks in the impermeable layers, press the water to the surface, where a series of surface streams define the landscape. Between the five deserts of the Eastern Cluster, the Cooper Creek, Diamantina, Georgina and Finca rivers all funnel waters from Australia's largest drainage basin into the epitome of Australian salt lakes. Lying above the Tirare Desert in the center of the Eastern Cluster, the Carthage Thunder, formerly known as Lake Eyre, is the lowest point on the Australian continent at 15 meters below sea level and the final destination of these waters. All of these streams are ephemeral rivers, meaning they run only when favourable conditions line up. Most years, they are chains of dry channels, water holes and flats. But after big rains in the wider catchment area, they switch on and behave less like a normal river network and more like a pulse-driven wetland system, fighting against the continental aridity. Despite the sources of water in the largest drainage basin of the continent, water reaches the Carthage Thunder only on rare occasions. Exceptional rainbursts are necessary to create a blanket of water on these salt pans. And in these instances, not just the Carthage Thunder, but the drainage basin as a whole transforms in its entirety. The shallow river courses easily overflow, creating vast wetland regions which make the whole basin explode with colour and life. Lush green grass patches scattered with wildflowers and the white and pink hues of salt and sediments create one of the most vivid pictures mother nature has to offer, right in the otherwise barren deserts of the eastern cluster. Even during times of flooding, however, Carthage Thunder barely fills to its maximum extent. Since surveys began in the 19th century, there have only been three instances where the salt pan of the lake is filled completely, connecting the two major basins into one continuous system. In these instances, which last occurred in 1974, the lake still only reached a depth of around 6 meters or 20 feet at its deepest levels, and with evaporation rates of up to 3.5 meters per year, it is always a short-lived spectacle. In 2025, after years of drought, Carthage Thunder finally filled again as it's visualized in this photo series created by NASA's Terra satellite, and the impacts on wildlife have been truly exceptional. Brine shrimp eggs, which have been dormant in the soil for years, suddenly come to life, and where floodwaters persist, fish follow, and then pelicans, banded stilts, and many other bird species join the feast. Once the wetlands fade again, the dire salt crust quickly returns, and the fauna that once was thriving in abundance now has to seek refuge in the mound springs of the Great Artesian Basin, waiting for the cycle to repeat. Overall, the ten deserts that make up the broader Great Australian deserts live in a constant anticipation of new water. Whether it be through brief erratic violent storms and flash floods, or ancient groundwater with temporary rivers fighting to complete their course, these biological pulses are an immaculate example of natural systems existing on the edge of what's possible. If you want to see the other side of the Australian water story, the Murray-Darling Basin is the perfect opposite. A temperate river system, not challenged by nature's constraints, but instead by human challenges. You can find that video here, or watch what YouTube thinks is best for you here. And thanks again to Geography for sponsoring this video. Test your geography knowledge in countless game modes, and send me a challenge for a duel to the username Factspark, and see if you can beat me in locating cities and natural features around the globe. Download the game now with the link in the description below. See you in the next one. Cheers.