Volcanic ash and pumice blanketed the countryside. Chimney Rock consists primarily of Brule clay interlayered with volcanic ash and Arikaree sandstone. Yellow birch, mountain ash, and mountain maple grow in the understory. The eruption deposited about of volcanic ash on the city. Pozzolana is a fine, sandy volcanic ash. Strato/composite volcanoes are made of cinders, ash, and lava. The casks are made of different woods like chestnut, cherry, oak, mulberry, ash and juniper. Huge amounts of coal ash and other waste is produced annually. Approximately 10% by weight of common wood ash can be recovered as pot ash. It may have originated in the open country created by lava, volcanic ash, and pumice. Borobudur lay hidden for centuries under layers of volcanic ash and jungle growth. Most states require no monitoring of drinking water near coal ash dump sites. Regular Roman concrete for example was made from volcanic ash (pozzolana), and hydrated lime. Plants absorb elements elevated by the fly ash from the soil. Maple is stiffer than ash, and cheaper.