According to the Planetary and Space Science Centre (PASSC) at the University of New Brunswick in Canada, there are 190 confirmed impact structures on Earth. Each is recorded in a database called the Earth Impact Database (EID). List of confirmed and possible impact structures The following tables list geological features on Earth that are known impact events as well as possible, but for which there is currently no confirming scientific evidence in the peer-reviewed literature, impact events. In order for a structure to be confirmed as an impact crater, it must meet a stringent set of well-established criteria. Some proposed impact structures are likely to eventually be confirmed, whereas others are likely to be shown to have been misidentified (see below). Recent extensive surveys have been done for Australian (2005), African (2014), and South American (2015) craters, as well as those in the Arab world (2016). A book review by A. Crósta and U. Reimold disputes some of the evidence presented for several of the South American structures. Overview Russia's Lake Cheko is thought by one research group to be the result of the famous Tunguska event, although sediments in the lake have been dated back more than 5,000 years. There is highly speculative conjecture about the supposed Sirente impact (c. 320 ± 90 AD) having caused the Roman emperor Constantine's vision at Milvian Bridge. The Burckle crater and Umm al Binni structure are proposed to be behind the floods that affected Sumerian civilization. The Kachchh impact may have been witnessed by the Harappan civilization and mentioned as a fireball in Sanskrit texts. Shortly after the Hiawatha Crater was discovered, researchers suggested that the impact could have occurred as late as ~12,800 years ago, leading some to associate it with the Younger Dryas impact hypothesis. James Kennett, a leading advocate of the Younger Dryas impact hypothesis said, "I'd unequivocally predict that this crater is the same age as the Younger Dryas." These claims were criticised by other scholars. According to impact physicist Mark Boslough writing for Skeptical Inquirer the first reports of the impact released by science journalist Paul Voosen focused on this being a young crater which according to Boslough "set the tone for virtually all the media reporting to follow". Boslough argued, based on evidence and statistical probability, that once the crater has been drilled and researched "it will turn out to be much older." He complained that