300 million BC: glass created from asteroid impact in central Australia

Scientists have discovered glass 2kms under the Warburton Basin, in a 400km-wide crater extending over South Australia, Queensland and the Northern Territory.

The Warburton Basin

The scientists - from the Australian National University’s School of Archaeology and Anthropology - believe that the glass was created when an asteroid hit the earth more than 300 million years ago, generating enough heat and pressure to melt rock into glass.

The resulting 400km-wide crater is the biggest asteroid impact zone yet discovered on Earth. It is significantly larger than the 180km-wide Chicxulub crater in Mexico, created some 66 million years ago in an event that is believed to have led to the extinction of the dinosaurs.

An asteroid hits Earth (NASA)

A new element in Australia's glass history
Prior to the Warburton Basin discovery, scientists had only speculated that natural glass could be found in Australia. They knew that asteroid impacts create natural glass and they knew that Australia has 26 craters created by asteroid impacts. However, until now there was no evidence that an asteroid impact in Australia had created natural glass.

The Warburton Basin discovery provides that evidence. It also provokes further speculation: is it possible that humans in what is now central Australia used asteroid-formed glass? Archaeological records indicate that humans started making articles such as knives and arrow heads from natural glass 75,000 years ago; how soon before we discover evidence that such practices took place in Australia?

(Original report in Tectonophysics; cited in NT News 24 March 2015)

75,000 BC: Humans start using glass

Probably as early as 75,000 BC, humans used naturally-occurring glass to make articles such as knives and arrow-heads.

Obsidian

Our use of naturally-occurring glass pre-dates any written records of the practice (e.g. the ancient Egyptians' use of glass) and it certainly pre-dates our ability to make glass.

Obsidian spear-head

The most common form of naturally-occurring glass is obsidian, formed when the heat of volcanoes melts rocks such as granite, which then become glassy upon cooling.

Other forms of naturally-occurring glass are:

• pumice, a glassy foam produced from lava
• fulgurites, glass tubes formed by lightning striking sand or sandy soil
• tektites, lumps or beads of glass probably formed during meteoric impacts.

Source: http://www.chemistryexplained.com/Ge-Hy/Glass.html

Ancient glass on the Bellarine Peninsula?
We have yet to find any mention of naturally-occurring glass on the Bellarine. However, there is a chance that somewhere in Australia there is natural glass formed by an asteroid impact.

Australia has 26 confirmed craters created by asteroids between five thousand and two billion years ago; and it has another 6 unconfirmed craters. (The confirmed craters are listed in the Earth Impact Datbase, maintained by the University of New Brunswick’s Planetary and Space Science Centre.)

Source: http://en.wikipedia.org/wiki/List_of_impact_craters_in_Australia)

Natural glass in the Sahara

Asteroids have been cited as the origin of naturally-occurring yellow-green glass in the Sahara Desert in Egypt and black glass across South-East Asia. Scientists believe that the glass in the Sahara Desert was formed thirty million years ago, when an asteroid exploded just above the earth into a fireball 10,000 times more powerful than the first atomic bomb. The explosion created surface temperatures of 1,800 degrees Celsius, melting the sand into thousands of chunks of yellow-green glass.

The same scientists believe that 800,000 years ago, another asteroid exploded just above the earth into a series of fireballs that melted the ground into black glass in Thailand, Vietnam, Cambodia and southern China.

Source: “Tutankhamun’s Fireball”. Horizon series. BBC. 2006. 
https://www.youtube.com/watch?v=FO61IKwRpis

What next for the Bellarine's glass-related history?

Natural glass from the Sahara

Australia has certainly been hit by asteroids; and it's likely that asteroids were implicated in forming natural glass. However, the scientists investigating the natural glass in Egypt and in S-E Asia note that in neither case is there a crater to serve as evidence of the asteroid's impact. Instead, they believe, the asteroids exploded above ground, leaving no crater, but nonetheless melting the ground under them into glass. So while it's possible that humans in what is now Australia used asteroid-formed glass in the past,  proof awaits the first finding of natural glass.