Ozark Mountains are a geologic and physiographic highland area of the central part of the United States. The mountain covers much of the part of the southern half of Missouri State and an extensive part of north central and the northwestern parts of Arkansas. The area also expands westward into the northeastern part of Oklahoma and an extreme southeastern part of Kansas. The Shawnee Hills of the southwestern part of Illinois that lie close to the eastern border of this area are commonly referred to as the Illinois Ozarks, but are usually not considered a part of the true Ozark Mountains.
Although the area is called as the Ozark Mountains, it is really an elevated and intensely dissected upland. In nature, the region is a broad arena in the region of the Saint Francois Mountains. The Ozark Highlands region, covering virtually 122,000 square kilometers (47,000 square miles), is by far the most wide-ranging hilly region between the Rocky Mountains and the Appalachian Mountains. Together, the Ouachita Mountains and the Ozark Mountains form a region called the United States Interior Highlands, and are occasionally called collectively, such as the eco-region, known as the Ozark Mountain Forests, comprises the Ouachita Mountains, even though the Ouachita Mountains and the Arkansas River Valley, both situated on the southern part of the Boston Mountains, are not generally considered a part of the Ozark Mountains.
The Ozark Mountains are made up of four chief physiographic sections, such as the Springfield Plateau, Saint Francois Mountains, Salem Plateau, and Boston Mountains. The landscape is typically tenderly rolling, excepting in the Boston Mountains, down the escarpments, dividing the Salem and Springfield Plateaus, and the Saint Francois Range where it is rocky. Karst features, like losing streams, springs, sinkholes and caves are regular in the limestone of the Springfield Plateau and copious in the dolostone rock layer of the Boston Mountains and Salem Plateau.
Missouri, which is recognized as "The Cave State" with more than 6000 caves, and most of these caves can be seen in the Ozark counties. The aquifer system of the Ozark Plateaus affects the movement of the groundwater in all regions, except the igneous hub of the St. Francois Mountains. Geographic features of the Ozark Mountains comprise dolomite and limestone glades, which are stony, desert-like region on hilltops. As kept open by episodic fires that restrict the growth of forbs and grasses in the shallow soil, glades are the abode to tarantulas, collared lizards, scorpions, cacti and other genus more typical of the wilderness southwest.
The Boston Mountains are the uppermost part of the Ozark Mountains. Summits can arrive at elevations of more than 2,560 feet (780 meters) with valleys 500 feet to 1,550 feet (472 meters), with a depth between 495 feet and 1485 feet (150 meters and 450 meters).
The Ozark Mountains hold ore deposits of zinc, lead, barite and iron. Several of these deposits have been washed-out by significant mining activities, but many leftovers and are presently being excavated in the Lead Belt of the southeastern part of Missouri. In the past, the lead belt about the Saint Francois Mountains and the three-state district lead-zinc mining area around Joplin in Missouri has been extremely significant resources of metals. Mining practices widespread during the early 20th century left considerable deserted underground mine crises and heavy metal pollution in the groundwater and topsoil in the Three-state district.