Tuesday, September 13, 2011

The Xingu River, Amazon Basin, Brazil

The Xingu River, which flows within the Amazon Basin of central-eastern Brazil, is shown in this Envisat image, which highlights the contrast between the rainforest and sprawling urbanisation.

The Xingu River flows northward approximately 2 100 kilometres from the Brazilian state of Mato Grosso into the Amazon River, the second longest river in the world after the Nile. The rivers that form the Xingu River are: Jatob , Ronuro, Batovi, Kurisevo and Kuluene, which is the Xingus main tributary.

Rapids and falls are plentiful, spanning 644 kilometres long, in the upper part of the Xingu, making only the lower portion of the river navigable. The river passes through partly unexplored country and is a rich area in terms of environment and cultural diversity, with some 14,000 indigenous people from nine different ethnic groups living along it.

In an effort to protect the indigenous people, the Xingu National Park, an area of 26,000 square kilometres, was created in 1961. The park has allowed 14 different tribes that were previously warring to learn to live together. But according to the Kaxi Amazon News Agency, ranchers and loggers have encroached on the park and threaten to pollute the river.

Last month Brazilian supermodel Gisele Bundchen endorsed a campaign by the Socioenvironmental Institute to protect the rain forest along the Xingu River from deforestation and pollution. The campaign is called Y Ikatu Xingu, which means clean and good Xingu water, in the native Kamaiura language. According to the Kaxi Amazon News Agency, Bundchen will tell the world that the Amazon's waters are in danger.

The Tapaj�s-Xingu moist forest ecoregion lies between the Tapaj�s, to the west of Xingu, and Xingu rivers and is home to over one hundred and sixty species of mammals and more than five hundred and fifty species of birds. However, the Transamazon Highway traverses this area and has increased the level of urbanisation, timber extraction and gold mining.

Urbanisation has increased all over the world with people moving away from rural areas to towns and cities. Brazil has a relatively high level of urbanisation with an estimated 8 out of 10 people living in cities roughly 144 million out of 180 million.

This growth needs to be monitored to ensure it proceeds on a sustainable basis, does not damage environmental resources and does not worsen the quality and life and safety of urban dwellers. The sheer scale of cities can make this difficult to achieve at least from down here on Earth.

Earth Observation-derived maps of land use change show how cities expand over time. Such information products are valuable to governmental organisations as well as conservation groups. In the field of risk management, satellite imagery can characterise urban environments to a degree of accuracy simply not available on the ground.

This 30 May 2006 image was acquired by Envisat's Medium Resolution Imaging Spectrometer (MERIS) working in Full Resolution mode to provide a spatial resolution of 300 metres. The image has a width of 462 kilometres.

French Guiana, South America

This rare, almost cloudless Envisat view of part of the northeast coast of South America stretches from the mouth of the Amazon River in Brazil to the territory of French Guiana, from where ESA's Earth Observation satellite was launched in 2002.

The coast is surrounded by a muddy-yellow plume of suspended sediment that issues from the Amazon River, by most measurements the greatest river in the world. The Amazon and its 1100 tributaries drain 40% of the entire South American continent. The River is responsible for 20% of all the freshwater discharged into the ocean from Earth's land surfaces.

Sediment carried all the way from the slopes of Andes is transported to the maze of channels making up the 270-km-wide mouth of the Amazon. Around three million cubic metres of silt is discharged into the ocean each day a daily volume greater than that of Egypt's Great Pyramid.

To the west is located the French overseas department of French Guiana, its border with Brazil demarcated by the Oyapock River. As an integral part of France, French Guiana is therefore the largest part of the European Union located outside Europe.

It was first settled by France in 1604 and was the site of penal settlements until 1951. In 1964 France chose Kourou in French Guiana as the site of its satellite launch base. Today the Centre Spatial Guyanais (CSG) is jointly supported by ESA and serves as Europe's spaceport. Kourou is located on the coast at about the middle of the image.

Some 90% of French Guiana remains covered by tropical forest and woodland, with its 195 506 inhabitants concentrated in low-lying coastal plains. There are 817 kilometres of highway in the territory but more than 3760 kilometres of navigable inland waterways.

This image was acquired on 16 October 2005 by Envisat's Medium Resolution Imaging Spectrometer (MERIS) in Reduced Resolution Mode, providing a spatial resolution of 1200 metres and an image swath of 1170 kilometres.

Monday, September 12, 2011

Bohai Bay, China

This Envisat image shows parts of the Hebei Province, the Tianjin Municipality and the Bohai Bay of the Peoples Republic of China.

Tianjin, China's third largest city, and Beijing, China's capital city, are located in the centre of the Hebei Province, but they are not part of it. The province borders Liaoning to the northeast, Inner Mongolia to the north, Shanxi to the west, Henan to the south and Shandong to the southeast.

Tianjin, located west of Bohai Bay (120 kilometers southeast of Beijing), is a prosperous city of 10 million inhabitants, surrounded by fertile farmland. Located between Beijing, to the northwest, and the Yellow Sea, to the southeast, the Tianjin Municipality has played an important part in Chinese history.

The city of Tangshan, located in Hebei 200 km east of Beijing, is situated to the north of the northernmost tip of the Bohai Bay curve. In the early hours of 28 July 1976, the deadliest earthquake of the twentieth century hit the sleeping city of Tangshan. With a magnitude of 7.8, the earthquake killed over 240 000 people and injured some 600 000.

China has a history of natural disasters, such as floods, droughts and landslides. Earth-observing satellites are particularly useful for tackling and monitoring environmental phenomena in China, the third largest country in the world, because of the countrys sheer size 9.6 million square kilometres and various types of terrain.

ESA, Chinas Ministry of Science and Technology (MOST) and the National Remote Sensing Centre of China (NRSCC) have jointly undertaken a wide-ranging research initiative called the Dragon Programme to encourage increased exploitation of ESA Earth observation (EO) satellite data within China as well as stimulate increased scientific co-operation in the field of EO science and technology between China and Europe.

There are currently 16 Dragon projects including agricultural and forest monitoring, water resource assessment, atmospheric chemistry, terrain measurement, the ocean environment and climate change, among others.

This image was acquired on 28 January 2007 by Envisats Medium Resolution Imaging Spectrometer (MERIS) instrument while working in Full Resolution mode.

Ganges Delta, Bangladesh

This Envisat image highlights the Ganges Delta, the worlds largest delta, in the south Asia area of Bangladesh (visible) and India. The delta plain, about 350-km wide along the Bay of Bengal, is formed by the confluence of the rivers Ganges, the Brahmaputra and Meghna.

The worlds largest mangrove forest, the Sundarbans, is located where the land meets the water. The Sundarbans forest spans Bangladesh and India, with each countrys forest listed as a UNESCO World Heritage site. The Sundarbans, which translates as 'beautiful forest' in Bengali, provide critical habitat for numerous species, including the Bengal tiger and the estuarine crocodile.

Pollution, human encroachment, soil erosion and rising sea levels threaten to submerge large parts of the forest into the sea. In the past two decades, four mangrove islands have sunk and more are threatened.

Southern Bangladesh is hit every year by cyclones and floods. In May this year, cyclone Aila formed in the Bay of Bengal and thrashed Bangladeshs southwestern coast, with the Sundarbans withstanding the worst. In November 2007, cyclone Sidr hit the country's southwestern coast, leaving more than 4000 people dead or missing.

The annual delta flooding leaves behind rich alluvial deposits, which are used to grow jute, the countrys main cash crop.

As radar images represent surface backscatter rather than reflected light, there is no colour in a standard radar image. This image was created by combining three Envisat Advanced Synthetic Aperture Radar acquisitions (20 January 2009, 24 February 2009 and 31 March 2009) taken over the same area. The colours in the image result from variations in the surface that occurred between acquisitions.

Saturday, September 10, 2011

Calcutta, India

This Envisat ASAR radar multicolour composite image is focused over Kolkata (large bright area centre left), the capital of the state of West Bengal, India.

The city is a river port located on the eastern bank of the Hugli River, a branch of the Ganges, making it the most important urban center of Eastern India . Its maximum elevation is about 9 metres above sea level.

The image shows topographically that eastward from the river, the land slopes away to marshes and swamplands. Similar topography is seen on the west bank of the river, that has confined the metropolitan area to a strip of five to eight kilometers width on either bank of the river.

The principal suburbs of Kolkata are Howrah (on the west bank), Baranagar to the north, South Dum Dum to the northeast, the South Suburban Municipality (Behala) to the south, and Garden Reach in the southwest are also visible.

The image is made of three ASAR images acquired on different dates and assigning a colour ( RGB ) to each date.

Dates of Acquisition: Red : 11 January 2004, Green : 30 May 2004, Blue : 24 August 2003

Mouth of the Danube, Romania

Flanked by imposing mountains, one of Europe's principal rivers reaches its end in this Envisat image. The Lower Danube River flows east then north to empty into the Black Sea its triangular Delta, a UNESCO World Heritage Site.

The image covers a major part of the territories of Moldavia, towards image top, along with a thin coastal slice of the Ukraine, Romania, in image middle, and Bulgaria, at the image bottom.

The apparent S-shaped mountain chain dominating the image is made up of the Carpathian Mountains starting top left and the Transylvanian Alps in the middle. There is actually a break in the mountains outside the border of the image, and it is through this gap that the Danube flows east. Towards image bottom are the Balkan Mountains.

The Danube has its source in Germany's Black Forest and is one of Europe's main traffic arteries. It flows through nine European countries for a distance of about 2850 kilometres. The image shows only some of the vast number of the Danube's total tributaries. Also visible are the Prut and Trotus Rivers towards the top of the image, and the Olt River passing through the Transylvanian Alps.

The Lower Danube region is an important European wetland ecosystem that has lost nearly 80% of its wetlands in the last century due to attempts at river dredging, land reclamation and flood control.

Now Romania, Bulgaria, Moldavia and Ukraine have joined together to preserve and restore wetlands with a project called the Lower Danube Green Corridor project, Europe's largest international wetland preservation effort.

Jewel in the crown is the triangle-shaped Danube Delta, projecting out from the coastline due to steady deposition of alluvial material. The Danube Delta was added to the United Nations Educational, Scientific and Cultural Organisation (UNESCO) World Heritage List in 1991. It hosts over 300 species of birds as well as 45 freshwater fish species in its numerous lakes and marshes.

This image was acquired on 28 September 2003 with Envisat's Medium Resolution Imaging Spectrometer (MERIS), working in Full Resolution 300-metre mode.

Friday, September 9, 2011

The Nile Delta and Sinai Peninsula

The fertile green territory of Egypt's Nile Delta provides a notable contrast to the bare desert of the Sinai Peninsula in this Envisat view.

Only 2.5% of Egypt's land area is suitable for agriculture, corresponding to the Nile Valley and Delta. These low-lying floodplains are some of the oldest intensively cultivated areas on Earth, supporting up to 1600 inhabitants per square kilometre.

The triangular shape of the Delta comes from the divergence of the branches of the Rosetta and Damietta branches of the Nile. The branches split at the base of the Delta and are separated by around 140 kilometres by the time they reach the Mediterranean coast 160 km north.

In 969 AD the city of Cairo was founded as a military camp at this strategic point of divergence, on the eastern side of the Nile. Its name was originally Al-Qahira, meaning 'the victorious'. By the 13th century it was one of the world's largest urban settlements, although its relative ranking declined in later centuries.

Today Cairo is a sprawling metropolitan settlement of 15 million inhabitants. It is the largest city in Africa and the thirteenth largest city in the world. It extends across the western side of the Nile. Against the green of the Delta it appears brown-grey in colour.

The city of Port Said is also visible to the northeast of Cairo, on the Mediterranean coast beside the Suez Canal. With half a million inhabitants, it is an important location for industry, trade and fishing.

Bounded by the Gulf of Suez to its west and a geological fault zone extending from Africa's Great Rift Valley along the Gulf of Aqaba to its east, the arid Sinai Peninsula is almost entirely uninhabited except for some coastal settlements.

Much contested throughout the 20th Century, the majority of the Peninsula is today under Egyptian rule. Egypt's border with Israel is visible in the image, with the Egyptian side appearing lighter south from the Mediterranean. This is apparently due to higher grazing pressure on the Egyptian side.

This 14 February 2005 image was acquired by Envisat's Medium Resolution Imaging Spectrometer (MERIS), working in Full Resolution Mode with a spatial resolution of 300 metres and width of 670 km.

Aral Sea, Central Asia

The Aral Sea in Central Asia is shown in this Envisat image. The Aral Sea, located on the border between Kazakhstan and Uzbekistan (to the south), is actually a lake rather than a sea. Over the last 40 years, the Aral Sea, once the fourth largest lake in the world, has evaporated to half its original surface area and a quarter its initial volume, leaving roughly a 36 000 square kilometre zone of dry white-coloured salt terrain now called the Aralkum Desert.

As its water level has dropped 13 metres since the 1960s, the Aral Sea has actually split into two the larger horseshoe-shaped body of water and a smaller almost unconnected lake to its north. This Small Aral Sea is the focus of international preservation efforts, but the Large Aral Sea has been judged beyond saving (the shallowness of its eastern section is clear in the image). It is expected to dry out completely by 2020.

The Small Aral Sea is still thought to be saveable, and several dikes have been constructed to cut it off from the Large Aral Sea preventing water loss and salt contamination - but shifting water levels have so far defeated these efforts. The channel connecting the two should soon dry up, preserving at least the Small Aral Sea. Meanwhile researchers are studying the salty Aralkum Desert to see how best to promote plant growth and stabilise the dusty dry lakebed.

Located about 200 kilometres east of the Aral Sea is the Baikonur Cosmodrome the Russian-operated space launch facility located in the south-central part of Kazakhstan. Built in 1955, the Cosmodrome, which is still the worlds largest space launch facility, covers 6 717 square kilometres and extends 75 kilometres from north to south and 90 kilometres from east to west. The base contains dozens of launch pads, five tracking-control centres, nine tracking stations and a 1500-kilometre rocket test range.

Although the name of the launch facility is Baikonur, the Cosmodrome is not actually located there but near the town of Tyuratam. The former Soviet Union, which Kazakhstan was part of prior to gaining its independence in 1991, intentionally gave it the misleading name of Baikonur, which is a mining town located about 300 kilometres northeast of the space centre, to conceal the actual location of the site.

Envisat acquired this image on 14 July 2006 with its Medium Resolution Imaging Spectrometer (MERIS) instrument while working in Full Resolution Mode to provide a spatial resolution of 300 metres. The image has a width of 545 kilometres.

Thursday, September 8, 2011

North Sea, 'contrails'

This Envisat image over the North Sea captures numerous aircraft condensation trails, or 'contrails', as well as parts of the Netherlands (upper right), Belgium (lower right) and England (lower left).

Exhaust emissions from jet aircraft contain large amounts of water vapour which, under certain atmospheric states, will condense to form ice crystals.

These act as condensation nuclei around which even more water vapour in the surrounding air condenses. The end result is the formation of an elongated cloud-like condensation trail in the sky.

Contrails can last anywhere from a few minutes to hours. They can also grow to form persistent artificial cirrus clouds that can last for days or weeks. Contrails and cirrus clouds could potentially have an impact on Earth’s climate by trapping the Earth's heat in our atmosphere in a similar way to greenhouse gases.

The various colours of green visible in the sea are due to sediments transported in the water.

This image was acquired by Envisat's Medium Resolution Imaging Spectrometer (MERIS) instrument on 21 March 2009, working in Full Resolution mode to provide a spatial resolution of 300 m.

Wednesday, September 7, 2011

Southern Florida, Cuba and the Bahamas

The shallow blue waters of the Bahamas as seen from Envisat 800km away in space, acquired by the Medium Resolution Imaging Spectrometer (MERIS).

The Bahamas consist of a chain of islands and shallow water banks extending 1400 km from Florida to the island of Hispaniola. All the islands are surrounded by coral reefs - 5% of all the world\'s coral reefs are concentrated here.

At the top left of the image is the southern tip of Florida, reaching from the circular Lake Okeechobee down through the Everglades all the way to Key West. The top of the curved archipelago of islands and associated coral reefs known as the Florida Keys is also visible.

At the image base is the island of Cuba, 145 km south of Florida: the shaded area on the south face of the island is the swampy Zapata Peninsula National Park, while the rounded dark zone east of it corresponds to the verdant Sierra Del Escambray mountain range, including the 1160-metre-high Pico San Juan, Cuba\'s second highest peak.

Between Florida and Cuba is the Cay Sal bank, appearing as a small area of light blue water. To the east is Andros Island, which can be seen, like most Bahaman islands, to be located on the east side of a shallowly-submerged water platform.

The Biminis are formed from the top left of this same platform. Above Andros Island is Grand Bahama, with Nassau on its east side.

This MERIS image was acquired in Full Resolution mode on 24 January 2004, with a spatial resolution of 300 metres covering an area of 670 km x 670 km.

Arctic Islands

This Envisat radar image features the eastern side of Ellesmere Island (left), the northernmost Canadian island, and portions of the northwest coast of Greenland (right), the worlds largest island.

Ellesmere Island, the worlds tenth largest island, is considered part of the Queen Elizabeth Islands, the northernmost cluster of islands in the Canadian Arctic Archipelago. Glaciers and ice caps cover some 80 000 sq km of Ellesmere Island.

Inglefield Land is visible in the bottom right corner with the gray colour contrasting against the white and aqua blue colours of an ice cap.

In the image, blue, purple and green colours represent the waters of Nares Strait, which comprises several bodies of water. The narrow passage between Inglefield Land and Ellesmere Island is the Smith Sound, which extends some 88 km from Baffin Bay to the south (not visible) to the Kane Basin (dark blue water located above Inglefield Land). Kane Basin is where Greenlands Humboldt Glacier, the largest known glacier in the world, discharges.

As radar images represent surface backscatter rather than reflected light, there is no colour in a standard radar image. This image was created by combining three Envisat Advanced Synthetic Aperture Radar acquisitions (2 February 2009, 14 April 2009 and 10 November 2009) taken over the same area. The colours in the image result from variations in the surface that occurred between acquisitions.

Tuesday, September 6, 2011

Korean Peninsula

The Korean Peninsula in East Asia is highlighted in this Envisat image. The 966-km long peninsula is located between the Sea of Japan (East Sea) to the east and the Yellow Sea to the west and is bounded by the Korea Strait to the south.

The peninsula is divided into two countries the Democratic People's Republic of Korea (North Korea) and the Republic of Korea (South Korea). North Korea, which covers about 55 percent of the peninsula, is bordered by China and Russia to the north. The border occurs below the area that juts out into the Yellow Sea on the west side.

North Korea (120,538 sq km) is divided into nine provinces, with Pyongyang as the capital. Pyongyang is located on the Taedong River (the dark blue body of water seen emptying into the Yellow Sea in the upper left hand of the image).

The capital of South Korea (98,477 sq km) is Seoul (seen in light green just off the western coast in the northwest of the country). Seoul, located some 50 km south of the North Korean border on the Han River, hosted the 1988 Olympic Games and served as one of the host cities of the 2002 FIFA World Cup.

Busan, also referred to as Pusan, is the largest port city in South Korea (located on the southeast) and the second largest metropolis, after Seoul. Busan, which hosted the 2002 Asian Games and served as one of the host cities for the 2002 FIFA World Cup, has officially announced its bid to host the 2020 Summer Olympic Games.

As visible in the image, the peninsula is largely mountainous and rocky, making less than 20 percent of the land arable. Because the waters around Korea provide excellent fishing grounds, fish is the peninsulas chief source of protein.

Named for the yellowish sand that colours its water, the Yellow Sea experiences fluctuations in climate due to winter and summer Monsoon conditions, with the sea surface temperature changing as much as 10 degrees Celsius. The Yellow Sea is one of the largest shallow areas of continental shelf in the world with an average depth of 44 metres and a maximum depth of 152 metres. It is 870 kilometres long and 556 kilometres wide.

The Sea of Japan (East Sea) is an enclosed arm of the Pacific Ocean that is bounded by Japan and Sakhalin Island to the east and Russia and Korea to the west. It has a mean depth of 1752 metres and a maximum depth of 3742 metres, with the northern and southern portions being more shallow and important fishing areas.

This image was acquired by Envisat's Medium Resolution Imaging Spectrometer (MERIS) instrument on 11 February 2007, working in Full Resolution mode to provide a spatial resolution of 300 metres.

Queen Elizabeth Islands, Canada

This Envisat image features the ice-connected Queen Elizabeth Islands, Baffin Island and the northwestern tip of Greenland the worlds largest island.

The Queen Elizabeth Islands, the northernmost cluster of islands in the Canadian Arctic Archipelago, include Ellesmere (the vertical land mass to the west of the dark-blue Baffin Bay), Devon (the bean-shaped island directly beneath Ellesmere), Axel, Heiberg and the Parry (seen directly west of Devon) and Sverdrup island groups (partially visible directly southwest of Ellesmere).

The total area of land in the islands, named in honour Queen Elizabeth II, is around 419 000 sq km with about one-fifth of it covered with land ice. The largest mass of ice is on Ellesmere, the largest and northernmost island in the Canadian Arctic.

On the eastern side of Baffin Bay, or the upper right hand of the image, is northwest Greenland. The dark brown colour of Inglefield Land contrasts against the white Humboldt Glacier, the largest known glacier in the world. Visible as whiteness stretching across the upper right hand of the image, the glacier rises some 100 m and discharges into Kane Basin (located above Inglefield Land).

The Arctic sea passage between northwestern Greenland and Ellesmere Island is Smith Sound, which extends some 88 km from Baffin Bay to the Kane Basin.

Baffin Island (visible in the lower right hand corner) covers an area of some 507 451 sq km, making it the largest island in Canada and the fifth largest in the world. Baffin Island is separated from Greenland on the north and east by Baffin Bay and Davis Strait.

The crescent-shaped portion on the left is Brodeur Peninsula, separated from Borden Peninsula by the Admiralty Inlet. Bylot Island is visible just off the northeastern tip of Borden.

This image was acquired by Envisats Medium Resolution Imaging Spectrometer (MERIS) instrument on 2 July 2007 working in Full Resolution mode to provide a spatial resolution of 300 metres.

Monday, September 5, 2011

Atacama Desert, Chile

This Envisat image was acquired over northern Chile's Atacama Desert, the driest place on Earth outside of the Antarctic dry valleys.

Bounded on the west by the Pacific and on the east by the Andes, the Atacama Desert only knows rainfall between two and four times a century. The first sight of green in this Medium Resolution Imaging Spectrometer (MERIS) image occurs some 200 kilometres west of the coast, at the foothills of the Western Cordillera, where wispy white clouds start to make an appearance.

There are some parts of the desert where rainfall has never been recorded. The only moisture available comes from a dense fog known as camanchaca, formed when cold air associated with ocean currents originating in the Antarctic hits warmer air. This fog is literally harvested by plants and animals alike, including Atacama's human inhabitants who use 'fog nets' to capture it for drinking water.

The landscape of the Atacama Desert is no less stark than its meteorology: a plateau covered with lava flows and salt basins. The conspicuous white area below the image centre is the Atacama Salt Flat, just to the south of the small village San Pedro de Atacama, regarded as the centre of the desert.

The Atacama is rich in copper and nitrates it has been the subject of border disputes between Chile and Bolivia for this reason - and so is strewn with abandoned mines. Today the European Southern Observatory (ESO) has located in high zones of the Atacama, astronomers treasuring the region's remoteness and dry air. The Pan-American Highway runs north-south through the desert.

Along the Pacific coast, the characteristic tuft-shape of the Mejillones peninsula is visible, where the town of Antofagasta lies just south of Moreno Bay on the southern side of the formation.

This MERIS full resolution image was acquired on 10 January 2003 and has a spatial resolution of 300 metres.

Mt. Etna, Italy

This Envisat image acquired on 25 November 2006 captures smoke spewing from Europes largest active volcano, Mt. Etna. The 3 350 metre-high volcano resumed eruptions in early September this year and entered its highly active phase on 5 November, according to the National Institute of Geophysics and Volcanic Studies.

Ash erupting from Mt. Etna, located in Sicily, Italy, forced local authorities to close the nearby Fontanarossa airport in eastern Sicily last weekend, but has caused no other reported disruptions or damage.

The Valle del Bove a 5.5 x 7 km depression is clearly seen in the image on the eastern side of the volcano. The most prominent morphological feature of Mt. Etna, the Valle del Bove was formed thousands of years ago as a result of a sector collapse on Etnas eastern flank.

Mt. Etna eruptions date back to 1500 B.C. with some 200 eruptions recorded since then. Despite its frequent eruptions, Mt. Etna is not generally considered dangerous. The last time it posed a threat was in 1992 when the Italian military had to divert lava streams with controlled explosions to keep it from reaching some 7 000 inhabitants of the town of Zafferana, located on Etnas lower slopes.

Satellite data can be used to detect the slight signs of change that may foretell an eruption. Once an eruption begins, optical and radar instruments can capture the various phenomena associated with it, including lava flows, mud slides, ground fissures and earthquakes. Atmospheric sensors onboard satellites can also identify the gases and aerosols released by the eruption, as well as quantify their wider environmental impact.

This image was acquired by Envisats Medium Resolution Imaging Spectrometer (MERIS) instrument while working in Full Resolution mode to provide a spatial resolution of 300 metres.

Saturday, September 3, 2011

Hawaii, USA

This Envisat image shows the volcanic islands of Hawaii in the Pacific Ocean. Hawaii, admitted as the 50th of the United States in 1959, is the only state comprised totally of islands. Visible in the image from right to left are the eight major islands the Big Island of Hawaii, Kahoolawe, Maui, Lanai, Molokai, Oahu, Kauai and Niihau.

Hawaii is also the only state that does not fall within the North American continent. The islands stretch more than 2575 km across the mid-Pacific Ocean and lie some 2367 km north of the equator and just over 4000 km southwest of North America.

All of the islands, projecting peaks of volcanic mountains, formed millions of years ago when fiery basalt rock erupted through a crack in the ocean floor. Having formed above a magma hotspot in the Pacific plate, Hawaii has some of the worlds largest active and inactive volcanoes.

The 4170-metre-high Mauna Loa volcano to the south of the Big Island of Hawaii is the worlds largest volcano by area and remains active. The smaller, taller, 4250-metre-high Mauna Kea is also located on the big island of Hawaii, which is home to five volcanoes in total.

The heights of mountains are generally measured from sea level; however, Mauna Kea rises a total of 10203 metres from the sea floor, so that if counted from base to peak this shield volcano is actually the tallest mountain on Earth.

The Hawaiian Islands enjoy lush tropical forests from the combination of heavy rainfall and fertile volcanic soil. Because of its tropical soil, Hawaii is the only U.S. state that grows coffee. More than one-third of the world's commercial supply of pineapples comes from Hawaii and most of the world's macadamia nuts are grown on the Big Island.

This 26 January 2007 image was acquired by Envisat's Medium Resolution Imaging Spectrometer (MERIS) working in Full Resolution mode to provide a spatial resolution of 300 metres.

An icy Sakhalin Island, Russia

The Sakhalin Island, a large elongated island located in the North Pacific, is featured in this Envisat image.

Sakhalin is roughly 948 km long and 160 km wide and covers some 76 400 sq km. The narrow Strait of Tartary (visible on the left in light gray) separates it from the east coast of Russia and the Strait of La P rouse separates it from the northern part of Japan.

The Western and Eastern Sakhalin Mountain Ranges run down the island side by side from north to south, separated by the Tym-Poronaiskaya Valley; Tym and Poronai are also the names of the islands main rivers. At 1609 metres, Mount Lopatin, on the Eastern Mountain Range, is the islands highest peak.

Sakhalin, a former penal colony and Soviet military outpost, is prone to earthquakes, which sometimes trigger mudslides, and is covered in ice during the winter months. The surrounding cool waters are very fertile and support enormous fisheries.

The fish in the Sea of Okhotsk (the black body of water peering beneath wind blown ice seen on the right) feed well over three million pairs of seabirds, according to the World Wildlife Fund. Sakhalin is also the only known feeding ground for the critically endangered Western Pacific Gray Whale.

Sakhalin has vast reserves of oil and gas, and international consortia of energy companies have entered into agreements to develop the resources.

This image was acquired by Envisat's Medium Resolution Imaging Spectrometer (MERIS) instrument on 26 February 2007, working in Full Resolution mode to provide a spatial resolution of 300 metres.

Friday, September 2, 2011

Oil palm plantations, Indonesia, South East Asia

This radar Envisat acquisition highlights Indonesias Kalimantan region in the southern part of tropical Borneo in South East Asia.

Borneo, the worlds third largest island, was once covered in dense rainforests. However, in the 1980s and 1990s these forests were cleared for their timber at an alarming rate.

Soon after, the global demand for palm oil increased and what was left of Borneos forests started being cleared for palm plantations (visible as square green patches).

Palm oil, the most widely produced edible oil, is mostly used in food products, such as breads, ice cream and chocolates, but is also found in commercial items, such as soap, plastic and cosmetics.

One of the reasons its demand has risen so sharply in recent years is because bio-diesel, a product of palm oil, is seen as a green alternative to fossil fuels. However, environmental organisations warn the cost of meeting this demand is devastating to the environment and the global climate.

The palm oil industry is one of the most important factors for the dramatic reduction of orangutan populations, according to WWF International. Scientists estimate that less than 60 000 orangutans remain in the wild on Borneo and Sumatra. The development of these plantations not only reduces their natural habitat, but also gives hunters and traders greater access to these great apes.

The northern part of the Tanjung Puting Biosphere Reserve is visible in the lower centre half of the image between Kumai Bay (left) and the Seruyan River (right). The reserve boasts a large diversity of forest ecosystems and a wealth of biodiversity, including the worlds most endangered species of orangutans.

This image was acquired on 23 April 2009 by Envisats Advanced Synthetic Aperture Radar (ASAR) instrument.

Amazon Basin, Brazil, South America

A large part of Brazil's Amazon Basin is shown here. The area is a low-lying valley almost entirely covered by tropical rainforest, criss-crossed by rivers including the mighty Amazon itself.

At first glimpse there appears to be no trace of mankind in this image, but a careful look reveals settlements and roads extending from top to bottom along the right hand side.

The Amazon River is the world's largest in terms of volume of water reaching the sea. The river's network also forms the world's largest drainage system, with around 1100 river tributaries. These tributaries are often referred to as 'white' or 'black' rivers. White rivers (their actual colour is yellowish) often rise in the Andes, their tint resulting from heavy loads of mud and silt. Black rivers, conversely, rise in rocky basements from where little or no sediment is carried along.

A beautiful example of the confluence of the Basin's main white and black rivers, the Solim es and the Rio Negro converging on the Amazon River, can clearly be seen.

A peculiarity of the Amazon is the lack of settlements along the river's banks, compared to the usual large ports, transport networks and industrialised cities found along important waterways. Among the only three sizable cities settled on the Amazon banks is Manaus on the right of the image, just north of the confluence.

Rainforests worldwide are being destroyed at an alarming concern, a development of great concern because they are essential to life on a global scale. Unlike other forests, rainforests do not grow back when they are destroyed and their soils are not suitable for continued agricultural use.

All countries in the Amazon region are now looking into ways of exploiting its natural resources in a sustainable manner without destroying the rainforest any further. Environmentalists and Indians are working together to create markets for products such as nuts, fruits, oils and pigments.

This image was acquired by Envisat's Medium Resolution Imaging Spectrometer (MERIS) on 4 October 2002, working in Full Resolution Mode providing 300 metre resolution.

Thursday, September 1, 2011

Nova Scotia, Canada

This Envisat image highlights the Canadian province of Nova Scotia, located on the eastern seaboard of North America. The province is made up of a mainland peninsula and Cape Breton Island (located to the east).

Nova Scotia is one of Canadas three Maritime provinces along with New Brunswick (visible in the upper left hand corner) and Prince Edward Island (visible to the east of New Brunswick, partially cloud-covered).

The Gulf of St. Lawrence is visible above Prince Edward Island, and the Northumberland Strait is visible between New Brunswick and Prince Edward Island. The Atlantic Ocean is visible to the south and east of the peninsula, and the Bay of Fundy is visible between the peninsula and New Brunswick.

With an area of 55 284 sq km, Nova Scotia is Canadas second smallest province, after Prince Edward Island. The main peninsula is 550-km long and has 7500 km of coastline. Because the province is not more than 130 km wide, no place in Nova Scotia is far from the sea.

This image was acquired by Envisat's Medium Resolution Imaging Spectrometer (MERIS) instrument on 22 October 2007, working in Full Resolution mode to provide a spatial resolution of 300 metres.

Fires and floodplains, Sudan, Africa

Numerous smoke plumes from burning fires are shown over southern Sudan in this Envisat image. Although the cause of these fires is unknown, agricultural fires in the region are common this time of year because the dry season begins in November. Deliberate fires are often set to burn out papyrus plants so grass can grow and feed livestock.

The Sudd (the lush green area running from the top left to the bottom centre of the image) is a network of channels, lakes and swamps. The size of France, it is one of Africas largest floodplains and provides watering and feeding grounds for many endemic mammals and birds as well as for large populations of migratory species.

The Sudd is created by the White Nile, which along with the Blue Nile forms the worlds longest river the Nile. The White Nile, also known in various sections as the Bahr-el-Abiad, Bahr-el-Jebel, Albert Nile and Victoria Nile, rises in the headwaters of Lake Victoria and runs through Uganda before entering Sudan and creating the Sudd. The Blue and White Nile Rivers come together in the north at Khartoum, Sudan's principal agricultural area.

For thousands of years the source of the Nile remained a mystery despite extensive efforts by the Greeks and Romans to locate it. The Sudd played a major role in keeping the origins of the Nile a mystery because explorers were not able to navigate through its swampy marshes. In 1858 British explorer John Hanning Speke became the first European to identify Lake Victoria as the Niles source.

Plans for the White Nile to bypass the Sudd to allow more water to reach the river downstream in the deserts of northern Sudan and Egypt resulted in the Jonglei canal. Construction began on the canal in 1978 but was suspended in 1983. Many conservation groups oppose the canal saying it will be disadvantageous to the areas indigenous tribes and wildlife.

This image was acquired on 11 December 2006 by Envisats Medium Resolution Imaging Spectrometer (MERIS) instrument while working in Full Resolution mode.