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As Pangea rifted apart a new passive tectonic margin was born, and the forces that created the Appalachian, Ouachita, and Marathon Mountains were stilled. Weathering and erosion prevailed, and the mountains began to wear away. [10] By the end of the Mesozoic, the Appalachian Mountains had been eroded to an almost-flat plain. [10]
The Appalachian Mountains are a barrier to east–west travel, as they form a series of alternating ridgelines and valleys oriented in opposition to most highways and railroads running east–west. This barrier was extremely important in shaping the expansion of the United States in the colonial era. [10]
The Ouachita Mountains (/ ˈ w ɒ ʃ ɪ t ɔː /), simply referred to as the Ouachitas, are a mountain range in western Arkansas and southeastern Oklahoma. They are formed by a thick succession of highly deformed Paleozoic strata constituting the Ouachita Fold and Thrust Belt, one of the important orogenic belts of North America . [ 3 ]
The geology of Arkansas includes deep 1.4 billion year old igneous crystalline basement rock from the Proterozoic known only from boreholes, overlain by extensive sedimentary rocks and some volcanic rocks. The region was a shallow marine, riverine and coastal environment for much of the early Paleozoic as multi-cellular life became commonplace.
The mountains are made of highly deformed metamorphic rocks, largely developed during the Precambrian age over 541 million years ago. The mountains include schists, gneisses, slates, and quartzites, and are extensively intruded by igneous bodies. The Blue Ridge Mountains contain the highest mountains in eastern North America south of Baffin Island.
These mountains were once part of a mighty uplifted mountain range that stretch from the Appalachian Highlands through Texas. [19] During the earliest Paleozoic Era, the continent that would later become North America straddled the equator. The Appalachian region was a passive plate margin, not unlike today's Atlantic Coastal Plain Province ...
On a map showing only metamorphic rocks, the Canadian Shield forms a circular pattern north of the Great Lakes around Hudson Bay.. The Canadian Shield is a large area of Archean through Proterozoic igneous and metamorphic rocks in eastern Canada and north central and northeastern United States.
A rural Ozarks scene. Phelps County, Missouri The Saint Francois Mountains, viewed here from Knob Lick Mountain, are the exposed geologic core of the Ozarks.. 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, and Oklahoma, as well as a small area in the southeastern corner of Kansas. [1]