Impactites

Impactites are terrestrial rocks that were created or modified as a result of a meteorite impact event. There are 4 types: tektites, impact glass, suevites and shatter cones. Let’s dive into each one of them:

1. Tektite

Tektites are a terrestrial rock that is transformed during a meteorite impact event. They are composed of homogeneous glass that is usually over 70% by weight of silica. After a large meteorite impact event, silica bearing minerals are ejected from the surface of the Earth into the atmosphere. This causes them to melt and form droplets which fall back to Earth, sometimes thousands of kilometers away from the original impact site. Occasionally tektites contain remnants of the meteorites that created them. Tektites take their name from Greek ‘tektos’ meaning ‘molten’. They are found in distribution areas or strewnfields,  related to their crater. There are several localities in the world that include:

• Moldavites: Moldavite glasses formed 15 million years ago during the impact of a giant meteorite in present-day Nördlinger Ries. Splatters of rocks that were melted by the impact cooled and most fell in south Bohemia – traversed by Vltava river, in German: Moldau, hence its name. They are a type of tektite and impactite. Although the event occurred in Germany, most specimens are found in Czech Republic due to the trajectory of the impact. Example:

• Indochinites: consequence of a huge meteorite impact 788.000 years ago in the Gulf of Tonkin (Vietnam).  The pieces rained down hundreds and thousands of kilometers away from the impact, in direction South-East, reaching Philippines and even Australia. They have diverse shapes and a characteristic black color. Example:

• Atacamaites: they are dated to be 7,8 million years old. Atacamaites appear to be derived from an impact involving an iron meteorite, likely a IIAB Group Iron. The crater has yet to be found but it is probably small and eroded. Example:
  

• Bediasites: originated in an area in the eastern part of the U.S. state of Texas centered on the small town of Bedias which is 119 km north west of Houston. They are found in about nine Texas Counties in an area of over 18.000 km2. Bediasites are part of the 34-million-year-old North American strewnfield coming from the Chesapeake Bay crater. Example:

• Ivory Coast: dark tektites related to the Bosumtwi Crater in Ghana.

2. Impact Glass

Another type of impactite is impact glass. Similarly to tektites, they are composed of a more or less homogeneous glass that melted after a large meteorite impact event. The difference is that tektites travel at high altitudes before landing back on Earth and impact glasses may stay in place or travel to nearby locations in low altitude trajectories (they are not ballistically ejected). There are several localities in the world, being among the most famous: Libyan Desert Glass and Pica Glass.

• Libyan Desert Glass: formed over 26 million years ago, this striking yellowish-green to golden-hued glass is found scattered across the vast expanse of the Sahara Desert, specifically in the remote border region between Libya and Egypt. Its origin is linked to a powerful cosmic event—most likely a massive meteorite impact or airburst explosion—that superheated the sands, melting and fusing them. This material is notably pure, composed of nearly 98% silica, making it one of the most pristine natural glasses known to science. The result is a collection of uniquely shaped fragments, varying in size, texture, color and translucency. Examples:

• Pica Glass: formed by the impact of a comet with the Earth in the north of Chile 12000 years ago. The tremendous amount of energy generated by the impact, made the sand of the desert melt, forming this glass. Then it solidified again. Inside this glass there are particles of the comet that mixed with the terrestrial material. This comet is known to have been similar to Comet Wild 2. This event took place in the same time that a great extintion took place in South America so more than likely, the 2 events are related. Example:

3. Suevite

Suevites are a type of terrestrial rock that formed during a meteorite impact event. They consist of angular fragments of native stones (breccia) that have sintered together due to a meteorite impact. They can be monomict or polymict depending on whether they have one or several types of stones within them. They are named after the Latin derivation for the Swabia province in Germany, where suevites were found near the Ries crater. There are many localities of suevites, some of the most notorious ones are: Nördlingen in Germany, Sudbury in Canada, Rochechouart in France, Gardnos in Norway or Vredefort in South Africa. Example from Gardnos:

4. Shatter cone

Shatter cones are a geological feature that are only known to form as a result of a meteorite impact or a nuclear explosion. They are evidence that the bedrock has been subjected to extremely high pressures, in the range of 2–30 gigapascals. That is equivalent to a shock wave of 2.000.000.000 to 30.000.000.000 kilos per square meter. Shatter cones have a characteristic conical shape that radiates from the top outwards. Usually they are convex although sometimes they can be concave, especially when located next to a larger cone. In fine-grained rocks, they form an easily recognizable pattern with dozens of thin grooves around the cone. Usually shatter cones point upwards and towards the impact place. Famous shatter cone localities are: Steinheim in Germany, Subdury in Canada and Agoudal in Morocco. Example from Agoudal: