January 31st, 2012 Category: Deserts

Iran - January 19th, 2012

The tan area near the center of this image is part of the Dasht-e Lut, a large salt desert in southeastern Iran. It is the world’s 25th largest desert. Iran’s geography consists of a plateau surrounded by mountains and divided into drainage basins. Dasht-e Lut is one of the largest of these desert basins, 480 kilometers (300 mi) long and 320 kilometers (200 mi) wide

Itis considered to be one of the driest places on Earth. The eastern part of Dasht-e Lut is a low plateau covered with salt flats. In contrast, the center has been sculpted by the wind into a series of parallel ridges and furrows, extending over 150 km (93 mi) and reaching 75 m (250 ft) in height. This area is also riddled with ravines and sinkholes. The southeast is a vast expanse of sand, like a Saharan erg, with dunes 300 m (1000 ft) high, among the tallest in the world.

Tags: Dasht-e Lut Iran Sand Dunes | | Leave a comment

January 31st, 2012 Category: Image of the day

USA - December 27th, 2011

This orthorectified image shows the city of San Francisco and the San Francisco Bay Area, a region of 7.15 million people in California, USA. It encompasses a land area of about 46.9 square miles (121 km2) on the northern end of the San Francisco Peninsula, giving it a density of about 17,179 people per square mile (6,632 people per km2). It is the most densely settled large city (population greater than 200,000) in the state of California and the second-most densely populated large city in the United States after New York City. Here, this area appears bright white.

What is frequently referred to as the San Francisco Bay is actually a system of several interconnected bays: the San Francisco Bay (bottom) is connected to the San Pablo Bay, which in turn is joined with the Suisun Bay, above the image center. Here, the bridges spanning these bays can be observed as thin white lines over the dark black waters. These are, moving from just above the center to the lower right corner of the full image, the Richmond-San Rafael Bridge, the San Francisco-Oakland Bay Bridge, the San Mateo-Hayward Bridge, and the Dumbarton Bridge.

Tags: ASAR California San Francisco San Pablo Bay Suisun Bay USA | | Leave a comment

January 31st, 2012 Category: Deserts, Dust Storms, Lakes

Chad - January 4th, 2012

Dust can be observed in the air over Nigeria, southwest of Lake Chad (center). The white smudge to the northeast, in Chad, is a dust storm in the Bodélé Depression, located at the southern edge of the Sahara Desert in north central Africa. The lowest point in Chad, dust storms from the Bodélé Depression are very common, occurring on average about 100 days per year.

Desertification in the region has been increasing, and Lake Chad, once one of the world’s largest water bodies, could disappear in 20 years due to climate change and population pressures, resulting in a humanitarian disaster in central Africa. The lake – surrounded by Cameroon, Chad, Niger and Nigeria – has shrunk by 90 per cent, going from 25,000 square kilometers in 1963 to less than 1,500 square kilometers in 2001.

The 30 million people living in the Lake Chad region are being forced into competing over water, and the drying up of the lake could lead to migration and conflicts. Fish production has recorded a 60 per cent decline, while pasturelands have been degraded, resulting in a shortage of animal feed, livestock and biodiversity. A radical change in water management techniques is needed to stem the diminishing flow of water into Lake Chad.

Tags: Bodélé Depression Cameroon Chad Dust Lake Chad Niger Nigeria Sahara Desert | | Leave a comment

January 31st, 2012 Category: Phytoplankton

Iran - January 19th, 2012

A green phytoplankton bloom can be seen in the Persian Gulf near sediments trailing off the coast of Iran. Although the amount of phytoplankton – tiny marine plants – in the top layers of the oceans has declined markedly over the last century, there are phytoplankton increases in coastal zones where fertiliser run-off from agricultural land is increasing nutrient supplies.

Scientists say the decline in the oceans appears to be linked to rising water temperatures. The decline – about 1% per year – could be ecologically significant as plankton sit at the base of marine food chains.
The decline is seen in most parts of the world, one marked exception being the Indian Ocean.

Tags: Iran Persian Gulf Phytoplankton | | Leave a comment

January 30th, 2012 Category: Vegetation Index

DRC - January 3rd, 2012

This FAPAR image shows the vegetation index of the border area by Tanzania (right), the Democratic Republic of the Congo (left), Rwanda and Burundi (above center). Visible in the top right corner is part of Lake Victoria, with the small Lake Kivu visible above center, north of the longer Lake Tanganyika.

The index is highest in the Democratic Republic of the Congo, as can be seen by the rusty red false coloring. The rest of the image shows generally good photosynthetic activity (green), with a few small patches of low activity (yellow) visible just northwest of the northern end of Lake Tanganyika.

Tags: Africa Burundi Democratic Republic of the Congo DRC FAPAR Lake Kivu Lake Tanganyika Lake Victoria Rwanda Tanzania | | Leave a comment

January 30th, 2012 Category: Volcanoes

USA - December 25th, 2011

This orthorectified image shows the island of Maui, the second-largest of the Hawaiian Islands at 727.2 square miles (1,883 km2) and the 17th largest island in the United States. Maui’s diverse landscapes are the result of a unique combination of geology, topography, and climate. Each volcanic cone in the chain of the Hawaiian Islands is built of dark, iron-rich/quartz-poor rocks, which poured out of thousands of vents as highly fluid lava, over a period of millions of years. Several of the volcanoes were close enough to each other that lava flows on their flanks overlapped one another, merging into a single island.

Maui is such a “volcanic doublet”, formed from two shield volcanoes that overlapped one another to form an isthmus between them. This image focuses on the larger, younger volcano to the east, Haleakalā, which rises to more than 10,000 feet (3,000 m) above sea level, but measures 5 miles (8.0 km) from seafloor to summit, making it one of the world’s highest “mountains”. The eastern flanks of the volcano are cut by deeply incised valleys and steep-sided ravines that run downslope to the rocky, windswept shoreline.

Tags: Haleakalā Hawaii Maui Orthorectification USA | | Leave a comment

January 30th, 2012 Category: Clouds, Image of the day

Cape Verde - January 19th, 2012

The roughly symmetrical patterns of swirls and curves in the clouds in this image are cloud vortex streets, also known as von Karman vortices. They were created by low-level winds rushing over the Cape Verde Islands off the coast of northwestern Africa.

Von Karman vortices form nearly everywhere that fluid flow is disturbed by an object. In this image, the “object” that is disturbing the fluid flow is the group of Cape Verde islands. As a prevailing wind encounters the island, the disturbance in the flow propagates downstream of the island in the form of a double row of vortices which alternate their direction of rotation.

Tags: Cape Verde Cloud Streets Kármán Vortex streets | | Comments (1)

January 30th, 2012 Category: Rivers, Sediments

Bangladesh - January 26th, 2012

Smoke and haze hang over northeastern India and Bangladesh, stretching from the valley of the Brahmaputra River, south of the Himalayas, down to the Bay of Bengal. Haze is common in this region, and develops as a result of pollution from cars, industry and smoke from agricultural fires.

Bangladesh is primarily a broad deltaic plain formed by the confluence of the Ganges, Jamuna and Meghna Rivers and their tributaries. Roughly 80 percent of the country’s 144,000 square kilometer area is fertile alluvial lowland called the Bangladesh Plain. Here, sediments can be seen through the haze in the Bay of Bengal by the edge of the plain.

Tags: Bangladesh Bay of Bengal Brahmaputra River Ganges River Haze India Meghna River | | Leave a comment

January 29th, 2012 Category: Mountains

Panama - December 24th, 2011

This orthorectified wide-swath ASAR image shows the mountains of Panama, a Central American country, bordering both the Caribbean Sea (above) and the Pacific Ocean (below), between Colombia (to the east) and Costa Rica (to the west).

The dominant feature of the country’s landform is the central spine of mountains and hills that forms the continental divide. The divide does not form part of the great mountain chains of North America, and only near the Colombian border are there highlands related to the Andean system of South America. The spine that forms the divide is the highly eroded arch of an uplift from the sea bottom, in which peaks were formed by volcanic intrusions.

The mountain range of the divide is called the Cordillera de Talamanca near the Costa Rican border. Farther east it becomes the Serranía de Tabasará, and the portion of it closer to the lower saddle of the isthmus, where the canal is located, is often called the Sierra de Veraguas. As a whole, the range between Costa Rica and the canal is generally referred to by geographers as the Cordillera Central.

Tags: Continental Divide Cordillera Central Cordillera de Talamanca Orthorectification Panama Serranía de Tabasará Sierra de Veraguas Wide-swath ASAR | | Leave a comment