Australasian strewnfield
The Australasian strewnfield is the youngest and largest of the tektite strewnfields. Recent estimates suggest it may cover 10%–30% of the Earth's surface.[1] Tektites are gravel-sized bodies composed of black, green, brown, or grey natural glass. They are formed from terrestrial debris ejected by meteorite impacts.[2]
The strewnfield is about c. 790,000-year-old.[3][4] It includes most of Southeast Asia (Thailand, Laos, Vietnam, Cambodia, and Southern China). The material from the impact stretches across the ocean to include the Philippines, Indonesia, Malaysia, and Java. It also reaches far west out into the Indian Ocean, and south to Australia and Tasmania. Since the 1960s, it has been accepted that the strewn field included Hainan in southern China to Australia or about 10% of the Earth's surface.[1] This was later extended by finds in Africa and Tasmania to 20%. Recent additional finds in northern Tibet and Guangxi increased the strewnfield to about 30% of the Earth's surface, or almost 150 million km2, or about the size of the entire world's landmass.[1]
The glass comes from the melting of local rocks due to the impact of a large meteorite. The assumed source is a 1.2-kilometer-wide topographic depression in Tasmania known as Darwin Crater. The crater is filled with 230 metres of sediments and breccia. A crater of that size would be caused by a meteorite 20 to 50 metres in diameter.
References
change- ↑ 1.0 1.1 1.2 Povenmire H; Liu W. and Xianlin I. 1999. Australasian tektites found in Guangxi Province, China. 30th Annual Lunar and Planetary Science Conference. Houston.
- ↑ French, B.M. 1998. Traces of catastrophe: a handbook of shock-metamorphic effects in terrestrial meteorite impact structures. LPI Contribution #954. Lunar and Planetary Institute, Houston, Texas.
- ↑ Schneider D.M. 2002. Tektites. The Meteoritical Society.
- ↑ Pillans, B., Simmonds, P. 2012 Tektites, minitektites and microtektites from the Kalgoorlie region, Western Australia. Australian Regolith and Clays Conference, Mildura, 7–10 February 2012.