Portal:Mountains

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Introduction

Silvretta panorama from the Ochsenkopf
Silvretta panorama from the Ochsenkopf

A mountain is an elevated portion of the Earth's crust, generally with steep sides that show significant exposed bedrock. A mountain differs from a plateau in having a limited summit area, and is larger than a hill, typically rising at least 300 metres (1000 feet) above the surrounding land. A few mountains are isolated summits, but most occur in mountain ranges.

Mountains are formed through tectonic forces, erosion, or volcanism, which act on time scales of up to tens of millions of years. Once mountain building ceases, mountains are slowly leveled through the action of weathering, through slumping and other forms of mass wasting, and through erosion by rivers and glaciers.

High elevations on mountains produce colder climates than at sea level at similar latitude. These colder climates strongly affect the ecosystems of mountains: different elevations have different plants and animals. Because of the less hospitable terrain and climate, mountains tend to be used less for agriculture and more for resource extraction, such as mining and logging, and recreation, such as mountain climbing and skiing.

The highest mountain on Earth is Mount Everest in the Himalayas of Asia, whose summit is 8,850 m (29,035 ft) above mean sea level. The highest known mountain on any planet in the Solar System is Olympus Mons on Mars at 21,171 m (69,459 ft). ( Full article...)

Selected mountain-related landform

African Rift Valley. From left to right: Lake Upemba, Lake Mweru, Lake Tanganyika (largest), and Lake Rukwa.

A rift valley is a linear shaped lowland between several highlands or mountain ranges created by the action of a geologic rift or fault. A rift valley is formed on a divergent plate boundary, a crustal extension or spreading apart of the surface, which is subsequently further deepened by the forces of erosion. When the tensional forces are strong enough to cause the plate to split apart, a center block drops between the two blocks at its flanks, forming a graben. The drop of the center creates the nearly parallel steeply dipping walls of a rift valley when it is new. That feature is the beginning of the rift valley, but as the process continues, the valley widens, until it becomes a large basin that fills with sediment from the rift walls and the surrounding area. One of the best known examples of this process is the East African Rift. On Earth, rifts can occur at all elevations, from the sea floor to plateaus and mountain ranges in continental crust or in oceanic crust. They are often associated with a number of adjoining subsidiary or co-extensive valleys, which are typically considered part of the principal rift valley geologically. ( Full article...)

Selected mountain range

Santa monica mountains canyon.jpg

The Santa Monica Mountains is a coastal mountain range in Southern California, next to the Pacific Ocean. It is part of the Transverse Ranges. Because of its proximity to densely populated regions, it is one of the most visited natural areas in California. Santa Monica Mountains National Recreation Area is located in this mountain range. ( Full article...)

Selected mountain type

Fjäll landscape in Padjelanta, Swedish Lapland

A fell (from Old Norse fell, fjall, "mountain") is a high and barren landscape feature, such as a mountain or moor-covered hill. The term is most often employed in Norway, Fennoscandia, the Isle of Man, parts of northern England, and Scotland. ( Full article...)

Selected climbing article

Solid rivets

A rivet is a permanent mechanical fastener. Before being installed, a rivet consists of a smooth cylindrical shaft with a head on one end. The end opposite to the head is called the tail. On installation, the rivet is placed in a punched or drilled hole, and the tail is upset, or bucked (i.e., deformed), the head is supported against the direction of the tail when upsetting so it will stay on place, the tail expands to about 1.5 times the original shaft diameter, holding the rivet in place. In other words, the pounding or pulling creates a new "head" on the tail end by smashing the "tail" material flatter, resulting in a rivet that is roughly a dumbbell shape. To distinguish between the two ends of the rivet, the original head is called the factory head and the deformed end is called the shop head or buck-tail.

Because there is effectively a head on each end of an installed rivet, it can support tension loads. However, it is much more capable of supporting shear loads (loads perpendicular to the axis of the shaft). ( Full article...)

Selected images

Selected skiing article

Shin-bang is a general sense of discomfort/pain in the lower anterior portion of the tibia that contacts with the tongue of the ski boot, especially when pressed against the boot. Shin-bang is not to be confused with shin-bite, a condition where your shin is rubbed raw due to irritation inside of the ski boot. ( Full article...)

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