The Magnesian escarpment is the most westerly of three prominent escarpments that run north-south in Wisconsin. [1] [2] [3] All three escarpments are formed by the edges of layers of sedimentary rocks. The easternmost and most prominent escarpment is the Niagara Escarpment formed where younger and harder layers of dolomite overlay softer sedimentary rocks. The Black River Escarpment is capped by another layer of relatively harder rocks, overlay older softer rocks. The rocks of the Magnesian layer overlay rocks of the Cambrian Period, the oldest sedimentary rocks that contain fossils.
Limestone is a type of carbonate sedimentary rock which is the main source of the material lime. It is composed mostly of the minerals calcite and aragonite, which are different crystal forms of CaCO3. Limestone forms when these minerals precipitate out of water containing dissolved calcium. This can take place through both biological and nonbiological processes, though biological processes, such as the accumulation of corals and shells in the sea, have likely been more important for the last 540 million years. Limestone often contains fossils which provide scientists with information on ancient environments and on the evolution of life.
Sedimentary rocks are types of rock that are formed by the accumulation or deposition of mineral or organic particles at Earth's surface, followed by cementation. Sedimentation is the collective name for processes that cause these particles to settle in place. The particles that form a sedimentary rock are called sediment, and may be composed of geological detritus (minerals) or biological detritus. The geological detritus originated from weathering and erosion of existing rocks, or from the solidification of molten lava blobs erupted by volcanoes. The geological detritus is transported to the place of deposition by water, wind, ice or mass movement, which are called agents of denudation. Biological detritus was formed by bodies and parts of dead aquatic organisms, as well as their fecal mass, suspended in water and slowly piling up on the floor of water bodies. Sedimentation may also occur as dissolved minerals precipitate from water solution.
The Niagara Escarpment is a long escarpment, or cuesta, in Canada and the United States that starts from the south shore of Lake Ontario westward, circumscribes the top of the Great Lakes Basin running from New York through Ontario, Michigan, and Wisconsin. The escarpment is the cliff over which the Niagara River plunges at Niagara Falls, for which it is named.
The Drakensberg is the eastern portion of the Great Escarpment, which encloses the central Southern African plateau. The Great Escarpment reaches its greatest elevation – 2,000 to 3,482 metres within the border region of South Africa and Lesotho.
A mesa is an isolated, flat-topped elevation, ridge or hill, which is bounded from all sides by steep escarpments and stands distinctly above a surrounding plain. Mesas characteristically consist of flat-lying soft sedimentary rocks capped by a more resistant layer or layers of harder rock, e.g. shales overlain by sandstones. The resistant layer acts as a caprock that forms the flat summit of a mesa. The caprock can consist of either sedimentary rocks such as sandstone and limestone; dissected lava flows; or a deeply eroded duricrust. Unlike plateau, whose usage does not imply horizontal layers of bedrock, e.g. Tibetan Plateau, the term mesa applies exclusively to the landforms built of flat-lying strata. Instead, flat-topped plateaus are specifically known as tablelands.
Quartzite is a hard, non-foliated metamorphic rock which was originally pure quartz sandstone. Sandstone is converted into quartzite through heating and pressure usually related to tectonic compression within orogenic belts. Pure quartzite is usually white to grey, though quartzites often occur in various shades of pink and red due to varying amounts of hematite. Other colors, such as yellow, green, blue and orange, are due to other minerals.
The Onondaga Limestone is a group of hard limestones and dolomites of Devonian age that forms geographic features in some areas in which it outcrops; in others, especially its Southern Ontario portion, the formation can be less prominent as a local surface feature.
A cuesta is a hill or ridge with a gentle slope on one side, and a steep slope on the other. In geology, the term is more specifically applied to a ridge where a harder sedimentary rock overlies a softer layer, the whole being tilted somewhat from the horizontal. This results in a long and gentle backslope called a dip slope that conforms with the dip of resistant strata, called caprock. Where erosion has exposed the frontslope of this, a steep slope or escarpment occurs. The resulting terrain may be called scarpland.
The Oak Ridges Moraine is a geological landform that runs east-west across south central Ontario, Canada. It developed about 12,000 years ago, during the Wisconsin glaciation in North America. A complex ridge of sedimentary material, the moraine is known to have partially developed under water. The Niagara Escarpment played a key role in forming the moraine in that it acted as a dam for glacial meltwater trapped between it and two ice lobes.
The Karoo Supergroup is the most widespread stratigraphic unit in Africa south of the Kalahari Desert. The supergroup consists of a sequence of units, mostly of nonmarine origin, deposited between the Late Carboniferous and Early Jurassic, a period of about 120 million years.
The Great Escarpment is a major topographical feature in Africa that consists of steep slopes from the high central Southern African plateau downward in the direction of the oceans that surround southern Africa on three sides. While it lies predominantly within the borders of South Africa, in the east the escarpment extends northward to form the border between Mozambique and Zimbabwe, continuing on beyond the Zambezi river valley to form the Muchinga Escarpment in eastern Zambia. In the west, it extends northward into Namibia and Angola. It is the combination of this escarpment and the aridity of Southern Africa that leads to the lack of navigable rivers in South Africa.
The West Elk Mountains are a high mountain range in the west-central part of the U.S. state of Colorado. They lie primarily within the Gunnison National Forest, and part of the range is protected as the West Elk Wilderness. The range is primarily located in Gunnison County, with small parts in eastern Delta and Montrose counties.
The geology of Hong Kong is dominated by igneous rocks formed during a major volcanic eruption period in the Mesozoic era. It made up 85% of Hong Kong's land surface and the remaining 15% are mostly sedimentary rocks located in the northeast New Territories. There are also a very small percentage of metamorphic rocks in the New Territories, formed by deformation of pre-existing sedimentary rocks (metamorphism).
This glossary of geology is a list of definitions of terms and concepts relevant to geology, its sub-disciplines, and related fields. For other terms related to the Earth sciences, see Glossary of geography terms.
Wisconsin, a state in the Midwestern United States, has a vast and diverse geography famous for its landforms created by glaciers during the Wisconsin glaciation 17,000 years ago. The state can be generally divided into five geographic regions—Lake Superior Lowland, Northern Highland, Central Plain, Eastern Ridges & Lowlands, and Western Upland. The southwestern part of the state, which was not covered by glaciers during the most recent ice age, is known as the Driftless Area. The Wisconsin glaciation formed the Wisconsin Dells, Devil's Lake, and the Baraboo Range. A number of areas are protected in the state, including Devil's Lake State Park, the Apostle Islands National Lakeshore, and the Chequamegon–Nicolet National Forest.
A tableland is an area containing elevated landforms characterized by a distinct, flat, nearly level, or gently undulating surface. They often exhibit steep, cliff-like edges, know as escarpments, that separate them from surrounding lowlands. Depending on either their size, other physical characteristics, or geographic location, the landforms comprising a tableland are individually referred to by a number of names including either butte, mesa, plateau, potrero, tepui, or tuya. Table Mountains are also a type of tableland. A homologous landform under the sea is called either a tablemount or guyot.
The Enon Formation is a geological formation found in the Eastern and Western Cape provinces in South Africa. It is the lowermost of the four formations found within the Uitenhage Group of the Algoa Basin, its type locality, where it has been measured at a maximum thickness of 480 metres (1,570 ft). Discontinuous outcrops are also found in the Worcester-Pletmos and Oudshoorn-Gamtoos Basins, including isolated occurrences in the Haasvlakte, Jubilee, and Soutpansvlakte Basins near the small town Bredasdorp.
The Black River Escarpment is a geological feature in Eastern Wisconsin. The escarpment runs parallel to and between the Niagara Escarpment and the Magnesian Escarpment. The escarpment marks the boundary between bedrock from Lower Magnesian limestone bedrock and earlier Black River limestone. The escarpment emerges from Green Bay, on Lake Michigan. The escarpment's boundaries are not always visible to the untrained eye, but are marked by cliffs in some regions.
The geology of Ontario is the study of rock formations in the most populated province in Canada- it is home to some of the oldest rock on Earth. The geology in Ontario consists of ancient Precambrian igneous and metamorphic rock which sits under younger, sedimentary rocks and soils.
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.
Black River Escarpment.