national monument. noun. Definition of national monument for English Language Learners. : a place (such as an old building or an area of land) that is owned and protected by a national government because of its natural beauty or its importance to history or science. Britannica.com: Encyclopedia article about national monument.
Brown or discolored water is caused by minerals, sediment, or rust that may accumulate in the water mains over time. When the water from your tap is brown this indicates a disturbance in the water main that stirs up these deposits.
Rain water is acidic because of the carbon dioxide in the air â the carbon dioxide dissolves slightly in water to make carbonic acid. When it rains, the water works on the limestone like the vinegar does on the egg. The water slowly dissolves the limestone, eventually forming caves, stalagmites, and stalactities. Hereâs a link that will explain the entire experiment and how you can do it at home!