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Archive for September, 2009

Mountains and Sand Dunes in Eastern Iran

32.8N 59.2E

September 30th, 2009 Category: Snapshots

Iran - September 24th, 2009

Iran - September 24th, 2009

Iran is one of the most mountainous countries in the world. Its geography consists of rugged mountain ranges, particularly in the west, that separate flatter basins and plateaux. This orthorectified image exemplifies the craggy peaks of a  long range of mountains in the province of South Khorasan, in eastern Iran.

The summits reach heights of 2000 meters, above sea level, while the steep slopes quickly slide down to a lower and flatter landscape at an elevation of about 800 meters. Patches of sand dunes can be observed at the foot of the slopes towards the lower left and at the top of the full image.

Ice-Free Foxe Basin in Late Summer, Canada – September 30th, 2009

67.7N 76.2W

September 30th, 2009 Category: Climate Change, Image of the day

Canada - August 26th, 2009Hudson Bay

Canada - August 26th, 2009

The waters of Foxe Basin, a shallow oceanic basin north of Hudson Bay, in Nunavut, Canada, located between Baffin Island (above) and the Melville Peninsula (left), appear greenish due to sediments and phytoplankton growth.

Foxe Basin is a broad, predominantly shallow depression, generally less than 100 metres (330 ft) in depth, while to the south, depths of up to 400 metres (1,300 ft) occur.

For most of the year, Foxe Basin is blocked by ice floes. In fact,  open pack ice is common throughout the summer and the basin is rarely ice-free until September.

In this image, taken in late August, very little ice is present, allowing the greenish waters to be observed. The nutrient-rich cold waters found in the basin are known to be especially favorable to phytoplankton and to have a high sediment content, explaining their color.

The numerous islands in the basin, including the rounded Prince Charles Island near the center, are important bird habitats. Bowhead whales migrate to the northern part of the basin each summer.

Also of note here is the bright white Barnes Ice Cap on central Baffin Island, north of Prince Charles Island. It covers close to 6000 km2 and has been thinning due to global warming. Between 1970 and 1984, the ice cap thinned 1.7 m. The ice cap is Canada’s oldest ice, being approximately 20,000 years old. It is a remnant of the Laurentide ice sheet, which covered much of Canada during the last ice age.

Greenish Waters of the Gulf of Tunis, Tunisia

36.8N 10.1E

September 30th, 2009 Category: Lakes

Tunisia - September 1st, 2009

Tunisia - September 1st, 2009

The peninsula of Cap Bon in far northeastern Tunisia is flanked by the Gulf of Tunis to the west and the Gulf of Hammamet to the east.  Tunis, the capital city of Tunisia, appears here as a grey area at the southern edge of the Gulf of Tunis.

In this image, the Gulf of Tunis is greenish in color from algal growth or sediments. The rest of the visible shoreline, including that of the Gulf of Hammamet, is mostly clear.

Moving inland south of the peninsula is a white salt lake called Sebkhel de Sidi El Hani. The site, the third-largest salt-lake in Tunisia, is located 25 km south-west of Sousse and 20 km east-south-east of Kairouan.

It usually dries out in summer, but occasionally retains water all year. Salinity is very high and salt crystals sometimes remain on the substrate even when there is water in the lake.

Mangla Dam Lake on Jhelum River, Pakistan

33.1N 73.6E

September 30th, 2009 Category: Lakes, Rivers

Pakistan - September 7th, 2009

Pakistan - September 7th, 2009

The Mangla Dam, located in Pakistan’s Mirpur District, is the twelfth largest dam in the world. It was constructed in 1967 across the Jhelum River, about 67 miles (100 km) south-east of the Pakistani capital, Islamabad.

The dam created a reservoir known as the Mangla Dam Lake, with a capacity of 7,250 million cubic metres, visible below the mountains in this orthorectified image.

Until 1967, the entire irrigation system of Pakistan was fully dependent on unregulated flows of the Indus and its major tributaries. The agricultural yield was very low for a number of reasons, the most important being a lack of water during critical growing periods.

This problem stemmed from the seasonal variations in the river flow due to monsoons and the absence of storage reservoirs to conserve the vast amounts of surplus water during those periods of high river discharge.

The Mangla Dam was the first development project undertaken to reduce this shortcoming and strengthen the irrigation system. The project was designed primarily to increase the amount of water that could be used for irrigation from the flow of the Jhelum and its tributaries. Its secondary function was to generate electrical power from the irrigation releases at the artificial head of the reservoir. The project was not designed as a flood control structure, although some benefit in this respect also arises from its use for irrigation and water supply.

Mar Chiquita: Central Argentina’s “Little Sea”

September 29th, 2009 Category: Lakes

Argentina - July 28th, 2009

Argentina - July 28th, 2009

The blue and green body of water here, in the northeast of the Argentine province of Córdoba, is the Mar Chiquita (in Spanish literally “Little Sea”) or Mar de Ansenuza. It is an endorheic salt lake and the largest of the naturally occurring saline lakes of Argentina.

The lake occupies the southern part of a depression that measures about 80 km (north–south) by 45 km (east–west). Its surface area varies considerably given its shallow depth (about 10 m), between averages of 2,000 and 4,500 km² (corresponding to maximum elevations of between 66 and 69 m above mean sea level).

Mar Chiquita is slowly diminishing in volume due to increased evaporation and elevation of its bottom, and is ultimately bound to turn into a playa (a salt flat). Here, salt flats can be seen along its northern shores.

Mar Chiquita is fed primarily by the saline waters of the Dulce River, coming from Santiago del Estero in the north after being joined by the Saladillo River. The lands around the lower course of the Dulce and Mar Chiquita are wetlands, populated by a large biodiversity (especially aquatic birds).

From the southwest the lake receives (irregularly) the flow of the Primero/Suquía and the Segundo/Xanaes rivers, as well as several streams.

The salinity of Mar Chiquita is quite variable, with measured extremes ranging from 250 g/l in times of low water levels to around 40 g/l in very humid years.