The Island in the Sky mesa/district of Canyonlands National Park, as seen from the Needles district.

Table Mountain, overlooking the city of Cape Town, South Africa.

Mesas in the Glass Mountains of western Oklahoma, USA.

A lone mesa in Douglas County, Colorado

Tucumcari Mountain is a mesa outside of Tucumcari, New Mexico.

A mesa (Spanish and Portuguese for "table") is the American English term for tableland, an elevated area of land with a flat top and sides that are usually steep cliffs. It takes its name from its characteristic table-top shape.

It is a characteristic landform of arid environments, particularly the Southwestern United States. Many examples are also found in Spain, Sardinia, North and South Africa, Arabia, India, Australia, badlands and in the mountainous parts of Wyoming, Idaho, Montana, Texas, and Oklahoma. Grand Mesa is a large mesa located in western Colorado in the Southwest United States.

The term "mesa" is used throughout the United States to describe a flat-topped mountain or hill. In Spanish such a landform is more usually known as a meseta.^[1]

Formation[link]

Mesas in the region of Logudoro in northern Sardinia.

Cerro Negro one of a few mesas near Zapala, Argentina.

Mesas are formed by weathering and erosion of horizontally layered rocks that have been uplifted by tectonic activity. Variations in the ability of different types of rock to resist weathering and erosion cause the weaker types of rocks to be eroded away, leaving the more resistant types of rocks topographically higher than their surroundings.^[2] This process is called differential erosion. The most resistant rock types include sandstone, conglomerate, quartzite, basalt, chert, limestone, lava flows and sills.^[2] Lava flows and sills, in particular, are very resistant to weathering and erosion, and often form the flat top, or caprock, of a mesa. The less resistant rock layers are mainly made up of shale, a softer rock that weathers and erodes more easily.^[2]

The differences in strength of various rock layers is what gives mesas their distinctive shape. Less resistant rocks are eroded away on the surface into valleys, where they collect water drainage from the surrounding area, while the more resistant layers are left standing out.^[2] A large area of very resistant rock, such as a sill may shield the layers below it from erosion while the softer rock surrounding it is eroded into valleys, thus forming a caprock.

Differences in rock type also reflect on the sides of a mesa, as instead of smooth slopes, the sides are broken into a staircase pattern called "cliff-and-bench topography".^[2] The more resistant layers form the cliffs, or stair steps, while the less resistant layers form gentle slopes, or benches, between the cliffs. Cliffs retreat and are eventually cut off from the main cliff, or plateau, by basal sapping. When the cliff edge does not retreat uniformly, but instead is indented by headward eroding streams, a section can be cut off from the main cliff, forming a mesa.^[2]

Basal sapping occurs as water flowing around the rock layers of the mesa erodes the underlying soft shale layers, either as surface runoff from the mesa top or from groundwater moving through permeable overlying layers, which leads to slumping and flowage of the shale.^[3] As the underlying shale erodes away, it can no longer support the overlying cliff layers, which collapse and retreat. When the caprock has caved away to the point where only a little remains, it is known as a butte.

Mesas on Mars[link]

There is a transitional zone on Mars known as the fretted terrain which lies between highly cratered highlands and less cratered lowlands. The younger lowland exhibits steep walled mesas and knobs. The mesa and knobs are separated by flat lying lowlands. They are thought to be formed from ice-facilitated mass wasting processes from ground or atmospheric sources. The mesas and knobs decrease in size with increasing distance from the highland escarpment. The relief of the mesas range from nearly 2 km to 100m depending on the distance they are from the escarpment.^[4]

See also[link]

• Butte
• Table (landform)
• Dissected plateau
• Potrero (landform)
• Table Mountain
• Tepui
• Tuya
• Mesa Verde National Park
• Nor'Wester Mountains

References[link]

1. ^ "meseta". DRAE. http://buscon.rae.es/draeI/SrvltGUIBusUsual?TIPO_HTML=2&TIPO_BUS=3&LEMA=meseta. 
2. ^ ^{a b c d e f} Easterbrook, Don J. (1999). Surface Processes and Landforms. Upper Saddle River, NJ: Prentice Hall. 
3. ^ Choreley, Richard J.; Stanley A. Schumm, David E. Sugden (1985). Geomorphology. New York: Methuen. 
4. ^ Baker, David M. Morphological Analyses of Mesas and Knobs in the Northwest Fretted Terrain of Mars; Constraints on the Presence and Distribution of Ice-Facilitated Mass-Wasting. Ed. Alexander K. Stewart and James W. Head. Vol. 40. Issue 2. pp. 72. United States: Geological Society of America (GSA) : Boulder, CO, United States, 2008.

For other uses of the title The Grid, see Grid (disambiguation).

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. (October 2010)

The Grid are an English electronic dance group, consisting of Richard Norris and David Ball (formerly of Soft Cell),^[1] with guest contributions from other musicians. They are best known for the hits "Swamp Thing", "Crystal Clear", "Rollercoaster", "Floatation", and "Cybernetic" (with Robert Fripp and Phil Manzanera).

Band members[link]

• Richard Norris (born 23 June 1965, London) - keyboards
• David Ball (born 3 May 1959, Blackpool, Lancashire) - keyboards
• Sacha Rebecca Souter (musician) (born 26 November 1963, Cockerton, County Durham) - Vocals

Biography[link]

The Grid formed in 1988 and had their first success with debut single, "Floatation", released on East West Records in 1990. They went on to release a string of ten UK hit singles and four albums,^[1] and toured the UK, Europe, Asia and Australia. The group's 1994 album Evolver reached #14 in the UK Albums Chart.^[1] The lead single from this album, "Swamp Thing", featuring elaborate banjo lines played by Roger Dinsdale. "Swamp Thing" proved to be a commercial success in the UK, Europe and Australia, reaching #3 in the UK^[1] and Australia and selling a total of one million copies.^{[citation needed]}

In 1996, Norris and Ball agreed to a hiatus period in order pursue individual music interests. Norris formed the Droyds, which went on to remix tracks by musicians including Armand Van Helden and Siobhan Fahey, and wrote the official biography of Paul Oakenfold (published in 2007): Ball reformed Soft Cell with Marc Almond, and also wrote music scores for films.^{[citation needed]} Norris has since formed the psychedelic duo, Beyond The Wizard's Sleeve, with DJ Erol Alkan, and has released a number of solo records and remixes under the name The Time and Space Machine.

The duo reunited in 2005, initially playing two gigs under the name GDM with female singer Misty Woods, before writing and recording new material as the Grid. A single, "Put Your Hands Together", was released in 2007 and an album, Doppelgänger, followed in 2008. Both were released on the Some Bizzare label. The album featured vocals by the British musician, Chris Braide.

Discography[link]

Albums[link]

Singles[link]

References[link]

External links[link]

• Grid Central - An Unofficial Page for The Grid
• Death of Roger Dinsdale.
• The Grid on allmusic.com
• The Grid MySpace page