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A graben is a section of crust that has lowered relative to the blocks on either side, which is a result of its bounding faults dipping towards each other. [2] The plural of graben can be either graben or grabens. Graben form low-lying features such as basins and rift valleys. [1] [2] They can be very long relative to their width.
Graben often occur side by side with horsts. Horst and graben structures indicate tensional forces and crustal stretching. Graben are produced from parallel normal faults, where the displacement of the hanging wall is downward, while that of the footwall is upward. The faults typically dip toward the center of the graben from both sides.
With crustal extension, a series of normal faults which occur in groups, form in close proximity and dipping in opposite directions. [4] As the crust extends it fractures in series of fault planes, some blocks sink down due to gravity, creating long linear valleys or basins also known as grabens, while the blocks remaining up or uplifted produce mountains or ranges, also known as horsts.
In physical geography and geology, a horst is a raised fault block bounded by normal faults. [1] Horsts are typically found together with grabens. While a horst is lifted or remains stationary, the grabens on either side subside. [2] This is often caused by extensional forces pulling apart the crust.
Throughout the 1970s and 1980s, Kentucky led the US in coal production. A well drilled in 1819 in salt water, in the South Fork of the Cumberland River revealed the first indications of petroleum in Kentucky. A rush to produce paraffin from oil in the 1850s prompted discoveries in Clinton, Cumberland, Allen, Barren, Meade, Wayne and Russell ...
Today, 22 of the 120 counties have fewer than 10,000 residents, and half have fewer than 20,000. The 20 largest counties by population all have populations of 49,000 or higher, and just 7 of the 120 have a population of 100,000 or higher. The average county population, based on the estimated 2023 state population of 4.526 million, was 37,718.
The median household income in Kentucky is $55,454, according to the U.S. Census Bureau. These 10 counties are the poorest in KY, ranking says. One has median income of $24K
Later, an apparent reversal in the polarity of tectonic subduction at the Laurentia-Taconic boundary caused the entire horst-graben structure to invert - the formerly deep graben between the two Tanglewood horsts was raised, while the two horsts subsided, causing the area of deposition of the Tanglewood member to shift to the area previously ...