Lakes Huron, Erie and Ontario

Three of North America’s five Great Lakes are pictured in this Envisat image: Lake Huron (left), Lake Ontario (right) and Lake Erie (bottom).

About 100,000 years ago, a major ice sheet formed over most of Canada and part of the US. As the ice sheet formed, giant glaciers flowed into the land carving out valleys and leveling mountains.

Some 14,000 years ago, higher temperatures began to melt the ice sheet, and meltwater filled the small and large holes left by the glaciers. Many of these holes today still contain water and form the thousands of lakes of the central USA and Canada. The biggest remnants of this process are the Great Lakes.

Covering an area of over 244,000 sq km and containing about 22,600 cubic km of water, together the Great Lakes form the largest connected area of fresh, surface water on Earth. The only place where more fresh water is contained is in the polar ice caps.

They have played an important role in North America’s economic development by providing a transportation system between the agricultural and mining regions on the western shores with the market centers on the East Coast. The ability to ship materials such as coal, iron and ore also gave rise to the steel and automobile industries in the area. Detroit – nicknamed ‘Motor City’ – is located on the Detroit River (lower left).

This image was acquired on 6 March 2010. Snow cover is evident across the land, and we can see ice build-up along some of the lakes’ edges.

A green algal bloom is also visible in Lake Erie. These toxic blooms have been a problem for the lake in recent years. Caused by heightened levels of phosphorus – found in fertilizers and common household products – finding its way into the water, these blooms have increased the size of the lake’s low-oxygen 'dead zone'.

This image is featured on the Earth from Space video program.

Photo credit: ESA

Cotopaxi and Antisana Volcanos

Ecuador’s northern highlands are pictured in this image from Envisat.

Near the top left of the image, the southern outskirts of Ecuador’s capital, Quito, appear as white dots. Quito is one of the highest capital cities in the world, at an elevation of 2850 m above sea level.

This area is part of the northern zone of the Andean Volcanic Belt. The belt was formed as a result of the Nazca and Antarctic tectonic plates moving under the South American plate – a geological process called ‘subduction’.

Near the bottom-left corner is the Cotopaxi stratovolcano. It is the second highest summit in the country at about 5900 m and one of Ecuador’s most active volcanoes, erupting more than 50 times since the early 1700s.

On the center-right side of the image is the Antisana volcano.

What look like white glaciers at the peaks of these mountains are actually artifacts of the radar echo – the surfaces of the summits are more or less directly facing the satellite, so the radar signal reflects straight back to the antenna.

This image was created by combining three Envisat radar passes from 4 June 2006, 20 January 2008 and 24 January 2010 over the same area.

Colors represent changes in the land’s surface between the three radar scans that make up this composite image. Some of the changes are distinct, such as the patchwork showing changes in agricultural plots near the top left. From Antisana to the west, the area is generally colorful, indicating ground movement.

East of Antisana, however, the area is less colorful, and therefore more stable.

This image is featured on the Earth from Space video program.

Image credit: ESA

Zambezi River, Zambia

This image from Envisat’s radar shows the Zambezi River’s floodplain in western Zambia.

The city of Mongu appears as a cluster of white radar reflections on the right side of the image. It is about 15 km from the river’s main channel – which appears light green, snaking down the left side of the image – but during the wet season, the waters rise right up to the edge of the town.

This image is a compilation of three acquisitions from Envisat’s radar. Each acquisition is assigned a color, and when combined show changes between the acquisitions.

The individual images were acquired on 1 March, during the wet season, 27 September and 26 December, when water levels were low, all during 2011. Combined, the psychedelic array of colors reveal how drastically the floodplain changes between seasons.

As the second largest wetland in Zambia, the Zambezi floodplain is a major spawning ground for fish. With about 80 different fish species, it serves as a source of livelihood to the local people, along with harvesting of other wetland resources like reeds and sedges for handicraft, and rice cultivation.

But this area is threatened by unsustainable fishing, animal poaching and the dredging of canals.

The Zambezi floodplains is just one of the over 2000 sites worldwide considered to be wetlands of international importance by the Ramsar Convention – an intergovernmental treaty for the sustainable use of wetlands. World Wetlands Day is observed on 2 February, the anniversary of the signing of the Convention.

ESA assists the Ramsar Convention through the GlobWetland project and the TIGER initiative ‘Looking After Water in Africa’, which provide satellite data to be used to monitor these precious resources.

This image is featured in the Earth from Space video program.

Image credit: ESA

Westfjords Peninsula, Iceland

This Envisat image was acquired over the Westfjords peninsula in northwest Iceland.

Located in the North Atlantic Ocean east of Greenland and immediately south of the Arctic Circle, Iceland is the westernmost European nation, and has more land covered by glaciers than the whole of continental Europe. The country sits on the mid-Atlantic Ridge, where two tectonic plates are moving away from each other, causing strong geothermal and volcanic activity.

The grey area that is somewhat shaped like a Christmas tree is land, while the colorful spaces between the 'branches' are long fjords – long, narrow arms of the sea that stretch far inland.

During the ice ages both ice and rivers carved deep valleys in the mountains. As the climate changed, most of the ice melted, and the valleys were gradually filled with salt water from the coast, giving birth to the fjords.

The white dots along one of the fjords close to the center of the image are radar reflections from Westfjords peninsula’s largest town, Ísafjörður. More radar reflections from other towns can also be seen scattered along the coastline.

This image, also featured in the Earth from Space video program, was created by combining three Envisat radar acquisitions from 11 September 2004, 14 April 2007 and 3 May 2008 over the same area.

Image credit: ESA

Dasht-e Lut Salt Desert

The Dasht-e Lut salt desert in southeast Iran is captured in this Envisat image.

The desert is often called the ‘hottest place on Earth’ as satellites measured record surface temperatures there for several years. The highest land surface temperature ever recorded was in the Lut Desert in 2005 at 70.7ºC, as measured by NASA’s Aqua satellite.

The light area in the center of the image are the long, parallel wind-carved ridges and furrows. The darker area to the east is an extent of massive sand dunes, some reaching up to 300 m tall.

In the upper-right section we can see a light green, shallow body of water that straddles Iran’s border with Afghanistan. With their arid surroundings, the wetlands in this border region have been a major source of food and fresh water for thousands of years, as well as an important stop for migratory birds. But irrigation expansion combined with droughts have caused the water levels in these wetlands to drop significantly – and some years even dry up.

In the lower-left we can see the white, snow-capped Jebal Barez mountains.

A major earthquake struck about 100 km east of the snow-caps in 2003, its epicenter near the ancient city of Bam (lower-central portion of image). Iran experiences frequent tectonic activity as several major fault lines cross the country.

This image was acquired by Envisat’s MERIS instrument on 2 April 2012 and is also featured on the Earth from Space video program.

Photo credit: ESA

Western Uganda

Lakes and mountains of western Uganda are captured in this Envisat radar image.

The area pictured is part of the Albertine Rift, a branch of the East African Rift where the Somali Plate is splitting away from the rest of the continent.

In the upper right corner is Lake George. With the equator running right through the middle, this body of water is recognized as a Wetland of International Importance by the Ramsar Convention, an intergovernmental treaty for the sustainable use of wetlands.

Its waters flow into the Kazinga Channel – known for its high concentration of hippopotami and Nile crocodiles – and then empty into Lake Edward at lower left.

The colors in the two lakes and connecting channel indicate changes in water level between acquisitions. On either side of the channel, large craters and crater-lakes dot the volcanic fields.

At the top of the image, we can see the foothills of the Rwenzori Mountains on the border between Uganda and the Democratic Republic of the Congo (west).

Its highest peak topping 5100 m, the mountain chain is home to numerous glaciers, waterfalls and lakes. However, climate change has negatively affected the glaciers, and subsequently the mountains’ vegetation and biodiversity.

To the south of the mountains, the bright pink, purple and green areas show where changes in the land’s surface occurred between the three radar scans that make up this composite image. These changes are primarily in vegetation as the land here is blanketed with agricultural plots. There is even a clear-cut line where agricultural activities end and the protected land begins.

This image was created by combining two acquisitions from Envisat’s radar on 14 June 2007, 14 February 2008 and 3 July 2008 over the same area and it is featured on the Earth from Space video program.

Photo credit: ESA

Red Tide Off the UAE

The coast of the United Arab Emirates hosts some of the largest desalination plants in the world. While the water they release may affect the coastal ecosystem, harmful and non-harmful algae blooms can also greatly affect the desalination plants. In particular, the local phenomenon known as the ‘red tide’ has affected desalination plants over the last four years, causing severe damage and sometimes bringing operations to a halt.

Satellite data can be used to identify and monitor red tide events – such as this one spreading from the Gulf of Oman into the Persian Gulf. This image was acquired by Envisat’s MERIS instrument on 22 November 2008.

Image credit: C-wams project, Planetek Hellas/ESA

Fernandina Volcano

ESA's Envisat satellite shows ground deformation around a volcano on Fernandina island in the Galápagos islands, following the eruption in April 2009. The caldera is outlined in white, and the lava flow produced by the eruption is also in white, stretching to the coast.

Interferometric Synthetic Aperture Radar – or InSAR – is a technique where two or more satellite radar images over the same scene are combined to detect slight changes between them. Tiny changes on the ground cause changes in the radar signal and lead to rainbow-colored patterns in the combined image.

Image credit: ESA/M. Bagnardi, University of Miami

Raystown Lake, Pennsylvania

This Envisat radar image is centered on the man-made Raystown Lake in the US state of Pennsylvania. Near the top of the lake – which appears as a snaking red and blue line – there is a bright white radar reflection from the Raystown Dam. The area pictured is part of the greater Valley and Ridge Appalachians, in the Appalachian Mountain range. The lines that cut through the image are the long, even ridges characteristic of this region. One of the significant ridges is Tuscoarora Mountain in the lower-right corner. This is a compilation of three radar images from 23 December 2007, 2 March 2008 and 11 May 2008.

This image is featured on the Earth from Space video program.

Image credit: ESA

New Zealand's South Island

New Zealand’s South Island is pictured in this Envisat image from 4 April 2012. There are a number of lakes throughout the island, but one that stands out in particular is Lake Pukaki, at the center of the image. The bright blue coloring of its waters comes from the extremely fine rock particles fed into the water from the glaciers. To the northeast, the light green coloring of Lake Ellesmere / Te Waihora can be seen. Peeking out from between the clouds to the south is Stewart Island/Rakiura – the country’s third largest island.

This image is featured on the Earth from Space video program.

Photo credit: ESA

Botswana's Okavango Delta

This image is a compilation of three images from Envisat’s radar and shows where southwestern Africa’s Okavango River empties into the inland Okavango Delta in northern Botswana. The Okavango River originates in Angola, forms part of the Angola Namibia border and then ends in northern Botswana. Here, it has formed a depression in the semi-arid Kalahari basin. Appearing purple at the center of the image is Chief’s Island. In the lower-right portion of the image we can see a large cluster of radar reflections from the town of Maun. At the top of the image, a triangle with similar coloring to the delta can be seen. This is a swamp area and national park located mostly in Namibia.

This image is featured on the Earth from Space video program.

Image credit: ESA

Istanbul, Turkey

Istanbul and the surrounding area in northwestern Turkey are captured in this image acquired by Envisat’s MERIS instrument on 9 June 2011. To the north is the Black Sea, which connects to the Sea of Marmara (center) via the Bosphorus strait. The Dardanelles strait connects the Marmara to the Aegean Sea (lower left corner). Turkey's largest city, Istanbul, is near the center of the image at the Bosphorus strait. Istanbul straddles two continents (Europe and Asia), making it a true meeting place of the East and the West.

Turkey’s location makes it vulnerable to earthquakes, with the 1000 km-long North Anatolian fault just 15 km south of Istanbul. Because earthquakes can suddenly render current maps out of date, satellite images are useful for updating views of how the landscape has been affected as well as creating reference cartography for emergency operations. In addition, before and after satellite images of the area enable authoritative damage assessment as a basis for planning remedial action.

Photo credit: ESA

Scandinavian Snows

In this image from the Envisat satellite, clouds cover the North Sea and sweep down to the strait between Denmark (lower-right corner) and Norway (upper-center). In the upper-right corner, a thicker blanket of clouds covers south eastern Norway and spreads into Sweden. Located on the Scandinavian Peninsula, Norway is Europe’s northernmost country and is famed for its fjords. Some of these are visible in the image as dark lines between the white and snow-covered land. Near the top of the image, we can see part of Norway’s longest and deepest fjord, the Sognefjord. In the lower-right corner, we can see part of Denmark’s Jutland peninsula, with small and large bodies of water speckling the flat terrain.

Text credit: ESA;Video credit: ESA

Note: The image shown in this video can be found here; unfortunately, at 13.42 MB, it is too large for Blogger to upload.

Cloudless British Isles

The lush landscapes of Ireland, Great Britain and northern France are pictured in this rare cloud-free view, acquired by Envisat on 28 March 2012.

To the west, thousands of lakes speckle the island of Ireland. Brown rugged cliffs along the coast frame its plush green interior. In the lower-right corner, the river Seine flows through Paris (seen here as a gray area) and snakes toward the English Channel. Following mainland Europe’s coastline north, we can see the Rhine–Meuse–Scheldt delta followed by part of the intertidal Wadden Sea in the extreme top-right corner. The green and tan-tinted swirls in the seas and channels are due to sediments being transported in the water. Sediment is particularly concentrated around Britain’s southeastern coast, carried by the River Thames through London and into the North Sea.

This image is featured on the Earth from Space video program.

Photo credit: ESA

Gulf of Guinea

This Envisat image shows West Africa around the Gulf of Guinea, with parts of Nigeria to the north and Cameroon to the east visible. Cameroon’s largest city of Douala is located near the Wouri estuary near the center of the image. North of the Wouri estuary, the Mount Cameroon volcano is clearly visible. The island of Bioko is pictured just off the coast.

Reflections of Envisat’s radar signal appear like specks of white throughout the image. They are particularly concentrated around cities such as Malabo on the island, Douala near the Wouri estuary and the populated areas of southern Nigeria. These white specks are the typical appearance of built-up areas in radar images, owing to the multiple reflection of the radar beam by buildings and especially metal constructions.

This image is a compilation of three images from Envisat’s radar, acquired on 6 February, 7 March and 6 April 2012 – just two days before communication with the satellite was lost.

Image credit: ESA

Santorini Rising

Model of vertical movement across Santorini from January 2011 to present, derived from data from the Envisat and TerraSAR-X missions. Over the past year and a half, parts of Santorini have risen by 14 cm, such as the Kameni islands in the center. Scientists believe that new molten rock has been squeezing up beneath the volcano at a depth of about 4 km, pictured here as a red dot.

Image credit: M. Parks

Atacama Desert

The southern Atacama Desert is pictured in this Envisat image, with the border of Chile (west) and Argentina (east) running down the middle. The Atacama is believed to be the driest desert in the world, and the lack of cloud cover in this image highlights the dry climate.

This image was acquired by Envisat’s MERIS instrument on 4 March 2012.

Photo credit: ESA

Note: The Atacama desert is where the various telescopes for the European Southern Observatory are located; it is also where scenes for the James Bond movie, Quantum of Solace, were filmed.

The Paraná River

The Paraná River cuts through this image of southern Brazil, acquired by the MERIS instrument on Envisat on 19 March. In the area pictured, the river marks the borders of the Brazilian states of Mato Grosso do Sul to the north and west, São Paulo to the east and Paraná to the south.

Agricultural structures are evident in the surrounding land. Near the center of the image, smoke from a fire was captured blowing southwest from its source.

Photo credit: ESA

A Crack on Pine Island Glacier

This Envisat image shows the Pine Island Glacier in West Antarctica and reveals a crack in the glacier’s tongue about 25 km long. The image was acquired by Envisat’s radar on 6 April 2012, just two days before contact with the satellite was lost.

Photo credit: ESA

Ground Deformation at the Nea Kameni Volcano

Evolution of ground deformation over Nea Kameni Volcano (Santorini, Greece) from March 2011 to February 2012. The animation was derived using data from Differential Interferometric Synthetic Aperture Radar analysis of Envisat’s radar data.

Video credit: ESA

Note: This particular island is famous for the volcanic eruption that destroyed the Minoan civilization living on the island of Thera, as Santorini was known at the time. The artwork that was preserved by the eruption is very beautiful.