What are Block Mountains?
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Most of the mountains that we see today have derived their names from the methods of their formations. Formation of mountains by the tectonic processes is known as "orogeny". It is a Greek word meaning; oros stands for "mountain" and genesis for "origin" or "creation". Our Earths' surface constitutes six pieces of Earth's crust and uppermost mantle, together referred to as the "lithospheric plates" or "tectonic plates". The crustal rocks are buried to tremendous depths and face hydrodynamic forces and tension. Volcanic eruptions, folding and buckling of the Earth's surface has resulted in 5 different types of mountains. They are Fold Mountains, Volcanic Mountains, Dome Mountains, Plateau Mountains and Block Mountains. Most of the mountains are formed due to the slow and gigantic movement.
What is a Block Mountain?
Block Mountains or Fault Block Mountains are massive in structure. They have very steep slopes. Generally, the topography of the Block Mountains is very smooth. They are usually tucked in the folded zones of some of the most primitive mountains. These folded zones have gradually lost their plastic properties. And as a result, mountain surfaces have been smoothened because of denudations. Tectonic actions continued and eroded these sections. After breaking, some of the sections rose to new ranges and horsts. The remaining sunk to form depressions and grabens. Due to the repeated actions of orogeny, they formed broad gently sloping folds. These folds were accompanied by faults. Lifted type Block Mountains has two steep sides exposing scarps on both the sides.
What are the theories of formation for the Block Mountains?
Before understanding the formation process of fault Block Mountains, we must first understand "faults". The cracks formed on the Earth's surface are called "faults". These pieces fit like a puzzle mosaic. Due to tectonic or seismic movements, these gigantic puzzle pieces moves. As a result, block of rocks gets displaced on either side of these faults. They can get tilted sideways or can be uplifted with incredible force. And on the other side of the fault the ground undergoes a depression. However, in due course of time, these depressions get filled with weathering and erosion debris. There are two formation theories of Block Mountains.
- Tension Theory: According to this theory, a weak point existed on the Earth's surface. This point experienced tremendous tension. This tension radiated from that point and pushed the side rocky crust. As a result, the side rocks went down. And in the middle, the central block remained stagnant along with the point of tension. So this central block was formed at a higher elevation than the side blocks.
- Compression Theory: According to this theory, the rock layers compressed the middle block. So forces acted inwards towards a point. Due to this compression, the middle block rose forming the Block Mountains. The middle chunk remained at a higher elevation than the side rock chunks.
What are the different types of Block Mountains?
There are two types of Block Mountains: Lifted and Tilted. Lifted type Block Mountains has two steep sides. Both side scarps are exposed. Sierra Nevada and Teton Mountains in Wyoming (North America) are the best examples of lifted type Block Mountains. Tilted type Block Mountains has one gentle slope. The other steep has an exposed scarp. These type of mountains are commonly seen in the Range and Basin region of the western United States, Rhine valley and south-central New England. Level block terrains are commonly seen in northern Europe.
What is the natural vegetation and wildlife of the popular Block Mountains?
Block Mountains support diverse species of flora and fauna due to its wide range of topographic features, temperature and precipitation.
- Sierra Nevada Block Mountains: The temperature of the Sierra Nevada ranges from temperate to extreme cold. The mountain range is found tilted towards the west. Mesozoic granite rocks are found along with metamorphosed sedimentary rocks. White Fir, Western Juniper, Aspen, Big Sage bush, Ponderosa pine and mixed subalpine forest contribute to the vegetation of the place. Mammals found in the Sierra Nevada Block Mountains are grizzly bears, marmots, gray fox, weasels, skunks, mountain lions, bobcats, coyote and mule deer. Among birds, woodpeckers, falcons, spotted owl, quail and herons are common.
- Teton Block Mountains: The Teton Block Mountains are famous for the Grand Teton National Park. The climate of the place is semi-arid. The temperature varies from 34 degree Celsius to -43 degree Celsius. There are seven lakes at the base of the Block Mountain. The mountain range supports 17 species of carnivores, 6 hoofed mammals, 4 species of reptiles, 5 species of amphibians, 300 species of birds and 16 species of fish. There are 900 species of flowering plants along with 7 species of conifers in the forest.
- Harz Block Mountains: The Harz forests have an annual rainfall ranging from 150 cm to 170 cm. It is very famous for its herb filled meadows and wildlife. Woodruff, Arnica and Golden saxifrage used for spleen disease treatment are found here. Lynxes, wild cats, badgers are foxes are some of the mammals found in this Block Mountains.
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