What caused this seven mile scar in the Australian outback seen on Google Earth?

By Matej Lipar & The Conversation US

The following essay is reprinted with permission from The conversationan online publication covering the latest research.

Earlier this year, a caver was looking at satellite images of the Nullarbor Plain when he came across something unexpected: a huge, mysterious scar etched into the rugged landscape.

The finding intrigued scientists, including my colleagues and me. Upon further investigation, we realized that the scar was created by a violent tornado that no one knew had occurred. We report the findings in new research published today.

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Tornadoes are a known threat in the United States and elsewhere. But they too happen in Australia.

Without the power of technology, this remarkable example of nature’s cruelty would have gone unnoticed. Studying tornado aftermath is important to help us predict and prepare for the next big twister.

Australia’s Tornado History

Tornado are violent, spinning columns of air that fall from thunderstorms to the ground, producing wind speeds that often exceed 200 kilometers per hour. They can cause massive destruction – uprooting trees, tearing apart buildings and throwing debris over great distances.

Tornadoes have been reported on every continent except Antarctica. They occur most often in the Great Plains region of the United States and in the northeastern India–Bangladesh region.

The earliest tornado observed by settlers in Australia occurred in 1795 in the suburbs of Sydney. But a tornado was not confirmed here by Western scientists until the late 19th century.

In recent decades, documented cases in Australia include a 2013 tornado which crossed north-east Victoria and traveled up to the New South Wales border. It produced winds between 250-300 kilometers per hour and damaged Murray River townships.

And 2016 produced a severe storm at least seven tornadoes in central and eastern parts of South Australia.

It is important for scientists to accurately predict tornadoes so we can issue warnings to communities. This is why the Nullarbor tornado scar was useful to study.

A whirlwind mystery

The Nullarbor Plain is a remote, dry, treeless stretch of land in South Australia. The man who discovered the scar had used satellite images from Google Earth to search for the Nullabor caves or other karst features.

Karst is a landscape covered by limestone with distinctive landforms. The discovery of the scar came to the attention of my colleagues and I through the collaborative network of scientists and explorers studying the Nullarbor Karst.

The scar stretches from Western Australia across the border to South Australia. It is located 20 kilometers north of Trans-Australian Railway and 90 kilometers east-northeast of Forrest, a former railway settlement.

We compared satellite images of the site over several years to determine that the tornado occurred between November 16 and 18, 2022. Blue circular patterns appeared next to the scar, indicating puddles associated with heavy rain.

My colleagues and I then traveled to the site in May this year to investigate and photograph the scar and the surrounding landscape.

Our results have been is published in Journal of Southern Hemisphere Earth Systems Science.

What we found

The scar is 11 kilometers long and between 160 and 250 meters wide. It bears striking patterns called “cycloidal marks,” which are formed by tornado suction vortices. This indicates that the tornado was no ordinary storm but a strong one F2 or F3 category, spinning with destructive winds of more than 200 kilometers per hour.

The tornado probably lasted between seven and 13 minutes. Characteristics of the scar indicate that the swirling wind in the tornado was moving in a clockwise direction. We also believe the tornado was moving from west to east – consistent with the direction of a strong cold front in the region at the time.

Local weather observations also recorded intense cloud cover and precipitation during that period in November 2022.

Unlike tornadoes that hit populated areas, this one did not damage homes or cities. But it left its mark nonetheless, eroding soil and vegetation and reshaping the Earth’s surface.

Remarkably, the scar was still clearly visible 18 months after the event, both on satellite images and on the ground. This is probably because the vegetation grows slowly in this arid landscape, so had not yet covered the erosion.

Predict and prepare

This fascinating discovery on the Nullarbor Plain shows how powerful and unpredictable nature can be – sometimes without us knowing.

Only three tornadoes have previously been documented on the Nullarbor Plain. This is probably because the area is remote with few eyewitnesses, and because the events do not damage properties and infrastructure. Interestingly, these three tornadoes occurred in November, just like this one.

Our research provides valuable insights into tornadoes in this remote and understudied region. It helps us understand when and under what conditions these types of tornadoes occur.

It also emphasizes the importance of satellite imagery to identify and analyze weather phenomena in remote locations and to help us predict and prepare for the next big event.

And finally, the results are a stark reminder that extreme weather can strike anywhere, anytime.

This article was originally published on The conversation. Read original article.