Alluvium, the silt, clay, sand, and other material transported and deposited by running water. The term excludes lake and ocean deposits and is usually restricted to geologically recent sediments. Alluvium is laid down in many places but occurs most extensively on flood plains (areas along streams that are subjected to flooding); in river deltas; and in alluvial fans, cones, and plains at the base of steep mountains. Some of the world's richest agricultural land consists of alluvial soil. Such regions are also among the most heavily populated on earth. Examples include the Nile River valley and the deltas of eastern and southeastern Asia.
While routinely scanning the stars, NASA scientists came across something they didn't expect to see: a vast area of space empty of stars, planets and matter.
The Freemasons is a secret organization that began in the 1700s and is still in existence today. Who are the Freemasons? And what do they do in their secret meetings?