Qualla: Acraman Impact Structure

Acraman Impact Structure: Introduction

Mon, 22 Jun 2026 00:00:00 GMT

Photo credit Public domain. From the air it looks almost gentle: a pale, near-circular smear of salt pan and low islands set into the rust-red scrub of the Gawler Ranges, about 20 kilometres across. Lake Acraman is an ephemeral playa, dry for most of the year, easy to fly over without a second glance. Yet this faint ring is the scar of one of the largest meteorite impacts known on the Australian continent. Roughly 580 million years ago, in the deep Precambrian, an asteroid slammed into what was then ancient bedrock, blasting out a crater that may have measured close to 90 kilometres across before hundreds of millions of years of erosion ground it down to almost nothing.

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Image: Public domain

Acraman Impact Structure: Reading a Crater That Barely Exists

Mon, 22 Jun 2026 00:00:00 GMT

Photo credit Dr. Martin Schmieder, Perth, CC BY-SA 3.0 de. Most famous impact craters announce themselves with a rim and a bowl. Acraman does the opposite. It is so deeply eroded that its true size has to be reconstructed by indirect means, and geologists still argue over the numbers. Some estimate an original collapse crater up to 85 to...

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Image: Dr. Martin Schmieder, Perth | CC BY-SA 3.0 de

Acraman Impact Structure: The Debris That Travelled East

Mon, 22 Jun 2026 00:00:00 GMT

Photo credit Dr. Martin Schmieder, Perth, CC BY-SA 3.0. The most remarkable evidence of Acraman lies not at the crater but more than 300 kilometres away, in the layered red rock of the Flinders Ranges. There, threaded through the Ediacaran shales of the Bunyeroo Formation and exposed in gorges such as Brachina, runs a distinct band of...

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Image: Dr. Martin Schmieder, Perth | CC BY-SA 3.0

Acraman Impact Structure: A Blast and the Dawn of Animal Life

Mon, 22 Jun 2026 00:00:00 GMT

Photo credit NASA, Public domain. Acraman's timing places it at a fascinating moment in the history of life. The impact debris in the Flinders Ranges sits within Ediacaran rocks, close to the very region that gives its name to the Ediacara biota, the strange soft-bodied creatures that represent some of the earlie...

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Image: NASA | Public domain

Acraman Impact Structure: Named, Discovered, Remembered

Mon, 22 Jun 2026 00:00:00 GMT

Photo credit Jesse Allen, Public domain. The structure carried its secret quietly until 1986, when geologists George E. Williams and Victor A. Gostin reported the discovery, and the independent recognition of its ejecta, in the journal Science. The lake, the impact structure, and nearby Acraman Creek all take their name...

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Image: Jesse Allen | Public domain