Rhyolite is the most silica-rich of volcanic rocks. It is generally glassy or fine-grained (aphanitic) in texture, but may be porphyritic, containing larger mineral crystals (phenocrysts) in an otherwise fine-grained groundmass. The mineral assemblage is predominantly quartz, sanidine, and plagioclase. It is the extrusive equivalent to granite.
The Ozarks, also known as the Ozark Mountains, Ozark Highlands or Ozark Plateau, is a physiographic region in the U.S. states of Missouri, Arkansas, Oklahoma and the extreme southeastern corner of Kansas. The Ozarks cover a significant portion of northern Arkansas and most of the southern half of Missouri, extending from Interstate 40 in central Arkansas to Interstate 70 in central Missouri.
The St. Francis River is a tributary of the Mississippi River, about 426 miles (686 km) long, in southeastern Missouri and northeastern Arkansas in the United States. The river drains a mostly rural area and forms part of the Missouri-Arkansas state line along the western side of the Missouri Bootheel.
The Wichita Mountains are located in the southwestern portion of the U.S. state of Oklahoma. It is the principal relief system in the Southern Oklahoma Aulacogen, being the result of a failed continental rift. The mountains are a northwest-southeast trending series of rocky promontories, many capped by 500 million-year old granite. These were exposed and rounded by weathering during the Pennsylvanian & Permian Periods. The eastern end of the mountains offers 1,000 feet (305 m) of topographic relief in a region otherwise dominated by gently rolling grasslands.
Taum Sauk Mountain in the Saint Francois Mountains is the highest natural point in the U.S. state of Missouri at 1,772 feet . The topography of Taum Sauk is that of an elongated ridge with a NNW-SSE orientation rather than a peak.
Elephant Rocks State Park is a state-owned geologic reserve and public recreation area encompassing an outcropping of Precambrian granite in the Saint Francois Mountains in the U.S. state of Missouri. The state park is named for a string of large granite boulders which resemble a train of pink circus elephants. The park was created following the donation of the land to the state in 1967 by geologist Dr. John Stafford Brown. The park is used for picnicking, rock climbing, and trail exploration. It is managed by the Missouri Department of Natural Resources.
Johnson's Shut-Ins State Park is a public recreation area covering 8,781 acres (3,554 ha) on the East Fork Black River in Reynolds County, Missouri. The state park is jointly administered with adjoining Taum Sauk Mountain State Park, and together the two parks cover more than sixteen thousand acres in the St. Francois Mountains region of the Missouri Ozarks.
The Musgrave Block is an east-west trending belt of Proterozoic granulite-gneiss basement rocks approximately 500 kilometres (310 mi) long. The Musgrave Block extends from western South Australia into Western Australia.
Taum Sauk Mountain State Park is a Missouri state park located in the St. Francois Mountains in the Ozarks. The park encompasses Taum Sauk Mountain, the highest point in the state. The Taum Sauk portion of the Ozark Trail connects the park with nearby Johnson's Shut-ins State Park and the Bell Mountain Wilderness Area, which together are part of a large wilderness area popular with hikers and backpackers.
The Mount Pleasant Caldera is a large eroded Late Devonian volcanic caldera complex, located in the northern Appalachian Mountains of southwestern New Brunswick, Canada. It is one of few noticeable pre-Cenozoic calderas, and its formation is associated to a period of crustal thinning that followed the Acadian orogeny in the northern Appalachian Mountains. It sits relatively near to the coastline.
The U.S. Interior Highlands is a mountainous region in the Central United States spanning northern and western Arkansas, southern Missouri, eastern Oklahoma, and extreme southeastern Kansas. The name is designated by the United States Geological Survey to refer to the combined subregions of the Ouachita Mountains south of the Arkansas River and the Ozark Plateaus north of the Arkansas. The U.S. Interior Highlands is one of few mountainous regions between the Appalachians and Rockies.
Hughes Mountain and the Hughes Mountain State Natural Area are located in southern Washington County, Missouri just south of the Big River and Highway M on Cedar Creek Road in the St. Francois Mountains range of The Ozarks. The mountain reaches an elevation of just over 1,200 feet, rising 430 feet above the Big River. The Hughes Mountain Natural Area of the Missouri Department of Conservation encompasses 462 acres (1.87 km2) of the mountain, including the rhyolite glade at its top.
The Spavinaw terrane is an occurrence of Proterozoic intrusive and volcanic rocks in the mid-continent region of the United States. The terrane extends across southern Missouri, southern Kansas, northern Arkansas and much of Oklahoma. The rocks are almost entirely known from drill core and only exposed in outcrop near Spavinaw, Mayes County, Oklahoma and parts of the Saint Francois Mountains in Washington County, Missouri. The terrane is composed almost exclusively of essentially unaltered intrusive granites and volcanic rhyolite and rhyolite tuffs.
The Cymru Terrane is one of five inferred fault bounded terranes that make up the basement rocks of the southern United Kingdom. The other notable geological terranes are the Charnwood Terrane, Fenland Terrane, Wrekin Terrane and the Monian Composite Terrane. In this article the definition of terrane is that implying rocks associated with the composition of the Precambrian basement. The Cymru Terrane is bounded to the northwest by the Menai Strait Fault System and to the southeast by the Pontesford Lineament. The geological terrane to the west is the Monian Composite Terrane and to the east is Wrekin Terrane. The majority of rocks in the area are associated with the outcrops that are evident at the faulted boundaries.
The Vishnu Basement Rocks is the name recommended for all Early Proterozoic crystalline rocks exposed in the Grand Canyon region. They form the crystalline basement rocks that underlie the Bass Limestone of the Unkar Group of the Grand Canyon Supergroup and the Tapeats Sandstone of the Tonto Group. These basement rocks have also been called either the Vishnu Complex or Vishnu Metamorphic Complex. These Early Proterozoic crystalline rocks consist of metamorphic rocks that are collectively known as the Granite Gorge Metamorphic Suite; sections of the Vishnu Basement Rocks contain Early Paleoproterozoic granite, granitic pegmatite, aplite, and granodiorite that have intruded these metamorphic rocks, and also, intrusive Early Paleoproterozoic ultramafic rocks.
The geology of Sudan formed primarily in the Precambrian, as igneous and metamorphic crystalline basement rock. Ancient terranes and inliers were intruded with granites, granitoids as well as volcanic rocks. Units of all types were deformed, reactivated, intruded and metamorphosed during the Proterozoic Pan-African orogeny. Dramatic sheet flow erosion prevented almost any sedimentary rocks from forming during the Paleozoic and Mesozoic. From the Mesozoic into the Cenozoic the formation of the Red Sea depression and complex faulting led to massive sediment deposition in some locations and regional volcanism. Sudan has petroleum, chromite, salt, gold, limestone and other natural resources.
The geology of Missouri includes deep Precambrian basement rocks formed within the last two billion years and overlain by thick sequences of marine sedimentary rocks, interspersed with igneous rocks by periods of volcanic activity. Missouri is a leading producer of lead from minerals formed in Paleozoic dolomite.
The geology of Alaska includes Precambrian igneous and metamorphic rocks formed in offshore terranes and added to the western margin of North America from the Paleozoic through modern times. The region was submerged for much of the Paleozoic and Mesozoic and formed extensive oil and gas reserves due to tectonic activity in the Arctic Ocean. Alaska was largely ice free during the Pleistocene, allowing humans to migrate into the Americas.
The geology of Wisconsin includes Precambrian crystalline basement rock over three billion years old. A widespread marine environment during the Paleozoic flooded the region, depositing sedimentary rocks which cover most of the center and south of the state.
