单词 | tektites |
释义 | tektitestektitestektitestektites(tek -tÿts) Small glassy rounded objects, about 0.1 to 3 cm in size, found only in certain parts of the world, often in vast strewn fields. They have shapes varying from spheroidal to pear-, lens-, and disk-shaped with surface-flow structures indicating that they were formed by rapid cooling of molten material. The chemical composition is that of silicic igneous rock with high SiO2 content (70–80%) and moderate Al2 O3 content (11–15%). They are named according to the place where they are found, e.g. moldavites (Moldavia), australites (Australia), etc. They were probably formed by the fusion of terrestrial material during the impact of giant meteorites; terrestrial and lunar volcanic origins have also been proposed. They are between 0.75–65 million years old. Small tektitelike objects have been found in the lunar regolith. |
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