St. Francois Mountains in the context of "Ozarks"

Missouri (see pronunciation) is a landlocked state in the Midwestern region of the United States. Ranking 21st in land area, it borders Iowa to the north, Illinois, Kentucky and Tennessee to the east, Arkansas to the south and Oklahoma, Kansas, and Nebraska to the west. In the south are the Ozarks, a forested highland, providing timber, minerals, and recreation. At 1.5 billion years old, the St. Francois Mountains are among the oldest in the world. The Missouri River, after which the state is named, flows through the center and into the Mississippi River, which forms the eastern border. With over six million residents, it is the 19th-most populous state of the country. The largest urban areas are St. Louis, Kansas City, Springfield, and Columbia. The capital is Jefferson City.

Humans have inhabited present-day Missouri for at least 12,000 years. The Mississippian culture, which emerged in the ninth century, built cities with pyramidal and other ceremonial mounds before declining in the 14th century. The Indigenous Osage and Missouria nations inhabited the area when European people arrived in the 17th century. The French incorporated the territory into Louisiana, founding Ste. Genevieve in 1735 and St. Louis in 1764. After a brief period of Spanish rule, the United States acquired Missouri as part of the Louisiana Purchase in 1803. Americans from the Upland South rushed into the new Missouri Territory, taking advantage of its productive agricultural plains; Missouri played a central role in the westward expansion of the United States. Missouri was admitted as a slave state as part of the Missouri Compromise of 1820. As a border state, Missouri's role in the American Civil War was complex, and it was subject to rival governments, raids, and guerilla warfare. After the war, both Greater St. Louis and the Kansas City metropolitan area became large centers of industrialization and business.

In geology, sial is an antiquated blended term for the composition of the upper layer of Earth's crust, namely rocks rich in aluminium silicate minerals. It is sometimes equated with the continental crust because it is absent in the wide oceanic basins, but 'sial' is a geochemical term rather than a plate tectonic term. As these elements are less dense than the majority of Earth's elements, they tend to be concentrated in the upper layer of the crust.

The uppermost layer of the crust is called the sial, consisting of silicate and aluminium (Si = silicate, Al = aluminium). On average, the thickness of the sial is till 25 km from the surface. The continents are composed mainly of lighter rock material formed from silicon and aluminium, so the sial is thick over the continents and very thin or absent on the ocean floor, especially the Pacific Ocean. Average density of the sial is 2.7 g/cm.