Definition: Rewrite each original sentence in order to make it easier to understand by non-native speakers of English. You can do so by replacing complex words with simpler synonyms (i.e. paraphrasing), deleting unimportant information (i.e. compression), and/or splitting a long complex sentence into several simpler ones. The final simplified sentences need to be grammatical, fluent, and retain the main ideas of their original counterparts without altering their meanings.
Input: Then, on December 21, 1994 the volcano spewed gas and ash which was carried as far as 25 km (16 mi) away by prevailing winds.

Then, on December 21, 1994 the volcano spewed gas and ash. Prevailing winds carried them as far as 25 km (16 mi) away.