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The Zones of Kilimanjaro
Tanzania
Stories about Mount Kilimanjaro often focus on its height and location. The tal est mountain in Africa is capped with snow and ice, despite sitting near the Equator. But it is also compel ing for a different reason: To get to the icy summit, you must pass through incredibly diverse vegetation zones. The mountain rises from the hot, dry savanna, through rainforest and hardy scrublands, to a rocky and icy summit.
People have cultivated the lowlands ringing the mountain, which appear as patchy green areas. The continuous dark-green band is montane forest, which stretches from roughly 1,800 to 2,800 meters in elevation. The dark-green areas transition to a band of green-brown known as the moorland zone—colder, less humid, and full of short, hardy plants. The highest areas—the alpine desert and summit zones—are inhospitable to all but the most skil ed mountain climbers.
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Liwa Oasis
United Arab Emirates
In the sandy tan terrain of the United Arab Emirates, on the northern edge of the Rub’ al Khali, an oasis brings green to the desert.
The T-shaped, 100-kilometer stretch of date plantations and small towns compose the Liwa Oasis, home to about 20,000 people in the emirate of Abu Dhabi. It is one of the largest oases on the Arabian Peninsula.
Bedouins tapped underground water supplies here at least five centuries ago, and date farms have proliferated. Drip irrigation and greenhouses now help conserve the precious water supply. Since rainfall is scarce in the region, much of the water comes from aquifers full of “fossil” water that accumulated more than 20,000 years ago and is now buried deep under the sand seas and limestone formations.
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Don Juan Pond
Antarctica
In a val ey in one of the most extreme environments on Earth lies the world’s saltiest body of water. It rarely snows and never rains in the McMurdo Dry Val eys of Antarctica. Winter temperatures can drop to –50° Celsius, and the few ponds and lakes are capped by ice that is several meters thick.
Then there’s Don Juan Pond. The ankle-deep pond in Upper Wright Val ey is so salty that its calcium chloride–rich waters rarely freeze. With a salinity level of over 40 percent, Don Juan is significantly saltier than the Dead Sea and the Great Salt Lake.
The Earth Observing-1 satel ite captured this image in January 2014. The el ipse-shaped lake is situated at the bottom of a basin between the Dais plateau and the Asgard Range to the south. It has a slightly darker hue than the salt-encrusted lake bottom around it.
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Linear Dunes, Caprivi Strip
Namibia
In far northeastern Namibia, there is a skinny stretch of land sandwiched between Angola, Botswana, and Zambia. The Caprivi Strip receives about 600 mil imeters (24 inches) of rainfall each year. That’s not a lot of rain—it tends to come in bursts that cause periodic floods—and it is a stark contrast to the much drier parts of the country.
Here the land is striped, as if a giant had dragged a rake over the landscape. Those stripes are linear dunes, and some of them are more than 100 kilometers (60 miles) long. Dunes general y form from wind-blown sand over many years, and one characteristic of linear dunes is that they tend to remain intact long after the dry conditions cease. And because they don’t migrate like marching dunes, linear dunes preserve dirt and rocks that geologists can later use to understand past conditions.
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Harratt Lunayyir Lava Field
Saudi Arabia
In northwestern Saudi Arabia lies a field of volcanic lava. Known as Harratt Lunayyir, the lava field contains some 50 cones from volcanic eruptions over the past 10,000 years. The Terra satel ite captured this false-color image in October 2006. Old lava flows appear as irregular, dark stains on an otherwise light-colored landscape. Like ink on an uneven surface, the lava has formed rivulets of rock that flow out in all directions.
Although one of the volcanic cones may have erupted as recently as the 10th century CE, scientists long believed the region to be geological y quiet until a seismic swarm and the opening of a crevice in 2009 suggested otherwise. The lava field Harratt Lunayyir lies about 200 kilometers (120 miles) from the tectonic spreading center under the Red Sea; magma can rise along the margins of such areas.
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Taranaki and Egmont
New Zealand
The circular pattern of New Zealand’s Egmont National Park stands out from space as a human fingerprint on the landscape.
The park protects the forested and snow-capped slopes around Mount Taranaki (Mount Egmont to British settlers). It was established in 1900, when officials drew a radius of 10 kilometers around the volcanic peak. The colors differentiate the protected forest (dark green) from once-forested pasturelands (light- and brown-green).
Named by the native Maori people, Taranaki stands 2,518 meters (8,260 feet) tal , and it is one of the world’s most symmetric volcanoes. It first became active about 135,000 years ago. By dating lava flows, geologists have figured out that small eruptions occur roughly every 90 years and major eruptions every 500 years. Landsat 8 acquired this image of Taranaki and the park in July 2014.
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Cultivating a Border
China and Kazakhstan
While people often say borders are not visible from space, this line between eastern Kazakhstan and northwestern China could not be clearer. The border is made visible due to land-use policies.
With limited arable land and a large human population to feed, China farms just about any land that can be sustained for agriculture.
In this Landsat 8 image from September 2013, fields are dark green in contrast to the surrounding dry landscape, a sign that the farms are irrigated.
While agriculture is important in the Kazakh economy, eastern Kazakhstan is a minor growing area for that country. A few rectangular shapes show that farming does occur. Much of the agriculture on the Kazakh side is rain-fed, so fields are tan like the surrounding, natural landscape.
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Barrier Islands
Brazil
Barrier islands are narrow strips of sand—often spits or sandbars that grow into ful -blown, vegetated islands. They stretch from a few hundred meters to several kilometers wide. They run paral el to the coast, facing the sea, bearing the brunt of waves and wind, and protecting lagoons, bays, and coastal wetlands. And they move constantly, shaped and reshaped by currents, tides, people, and winds.
Barrier islands are found along the edge of every continent except Antarctica, and scientists and naturalists are still finding new ones. In June 2006, Landsat 5 captured this image of previously unrecognized barrier islands along the coast of Brazil between the Amazon River and São Luís. Brazil has the world’s longest continuous chain of barrier islands—54 in total—extending more than 570 kilometers (350 miles) along the Atlantic coast.
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Tsauchab River Bed
Namibia
The Tsauchab River is a famous landmark for the people of Namibia and tourists. Yet few people have ever seen the river flowing with water. In times past, when the climate was more temperate, the Tsauchab likely reached the Atlantic coast, 55 kilometers to the west.
Like several other rivers around the Namib Desert, the Tsauchab brings sediment down from the hinterland toward the coastal lowland. This sediment is then blown from the river beds, and over tens of mil ions of years it has accumulated as the red dunes of the Namib Sand Sea.
In December 2009, an astronaut on the I
nternational Space Station caught this glimpse of the Tsauchab River bed jutting into the sea of red dunes. It ends in a series of light-colored, silty mud holes on the dry lake floor.
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It seems to me that the natural world is
the greatest source of excitement; the
greatest source of visual beauty; the
greatest source of intellectual interest.
It is the greatest source of so much in life
that makes life worth living.
—David Attenborough
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ice and snow
Mertz Loses Part of Its Tongue
Antarctica
The Mertz Glacier flows off East Antarctica and forms a long, narrow tongue pointing in the direction of Australia and New Zealand.
That tongue routinely calves icebergs into the Southern Ocean, and the Earth Observing-1 satel ite spotted it doing just that in January 2010.
Deep cracks, or crevasses, give the glacier tongue a rough and rugged texture, which carried over to this rippled iceberg. Such ice is often swept up by ocean currents circling Antarctica, and icebergs can remain relatively intact for months or years, so long as they remain in sufficiently cool conditions. Some icebergs, however, drift northward to warmer climates and disintegrate. By observing the response of an iceberg to warmer conditions, scientists can make predictions about how ice shelves—thick slabs of ice attached to coastlines—might respond to a warming climate.
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Swimming with Ice Cubes
United States
The ice season on the Great Lakes was longer in 2013–14 than anything in the satel ite records to date or in anyone’s memory. For nearly seven months, ice was afloat somewhere on the Great Lakes. In an average year, the lakes are ice-free by late April or early May—even as air temperatures onshore approached 27° Celsius (80° Fahrenheit) on some days. In 2014, the last ice melted in mid-June.
On May 23, 2014—the start of Memorial Day weekend (and unofficial start of summer in the United States)—Landsat 8 captured this image of ice in Lake Superior near Chequamegon Bay, Wisconsin. Satel ite imagery of ice is one of many tools that government agencies use to manage shipping on the Great Lakes.
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Franz Josef Land
Arctic Ocean
Located just 1,000 kilometers (600 miles) from the North Pole, Franz Josef Land is perpetual y coated with ice. Glaciers cover roughly 85 percent of the archipelago’s land mass, and sea ice floats in the channels between islands even in the summertime.
The Terra satel ite observed some of the islands in visible and near-infrared light in August 2011.
The amount of sea ice fil ing the channels between the islands of Franz Josef Land varies from summer to summer. Most of the ice in this scene is anchored to land, as large glaciers blanket the islands. Yet today’s glaciers are tiny compared to the ice sheet that dominated the region about 20,000 years ago. Raised beaches, which preserve evidence of land rising as the crushing weight of overlying glaciers eases (known as isostatic rebound), were first recognized on the islands in the late 19th century.
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No Green in This Land
Greenland
Ranging in color from snow white to turquoise, sea ice lined the shoreline of eastern Greenland in June 2000 when Landsat 7
acquired this image. Snowcaps form dendritic patterns on the brown landscape, leaving south-facing slopes especial y bare.
On the eastern promontory, “fast ice” clings to the shoreline. Common over shal ow ocean waters along shorelines, fast ice holds fast to the shore or sea bottom, not moving with winds or currents. Off the coast, pieces of bright white sea ice float on the sea surface at the whim of the elements.
Some of the fast ice in this image is blue, likely because it is composed of large crystals that were stretched by the relentless, transformative action of wind.
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Mackenzie Meets Beaufort
Canada
The intersection of Canada’s Mackenzie River and the Beaufort Sea is beautiful, and it is also important to the health of the Arctic ice cap. Research has shown that fresh water flowing from rivers into the Arctic Ocean can have a significant effect on the extent of sea ice cover. Warm-water discharges can accelerate the melting of sea ice near the coast. It also can create more open water, which is darker than ice and absorbs more heat from sunlight.
In the image, tan and brown water masses show up on both sides of the sea ice that crowds the shoreline of the river delta. A massive pulse of warm river water—colored by sediments and organic material flowing out from the Canadian interior—flows right under the ice. The pulse raised offshore water temperatures across hundreds of kilometers and seemed to contribute to the melting and dispersal of nearby sea ice.
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Sea Ice at Shikotan
Japan and Russia
Ostrov Shikotan is a volcanic island at the southern end of the Kuril chain. At about 43 degrees north—more than halfway to the Equator—Shikotan lies along the extreme southern edge of winter sea ice in the Northern Hemisphere. The Earth Observing-1
satel ite captured this image of swirling blue-gray sea ice around Shikotan in February 2011.
The ice here tends to move with currents and eddies, which has shaped it into rough circles. The eddies may result from opposing winds from the north and southwest.
Uneven snow cover exaggerates the island’s rugged appearance. Multiple forces have shaped Shikotan over mil ions of years. It has been battered by tsunamis—although wind, rain, and tectonic forces likely play a greater role in shaping the surface.
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North Patagonian Icefield
South America
Forests, grasslands, deserts, and mountains are all part of the Patagonian landscape that spans more than a mil ion square kilometers of South America. Toward the western side, expanses of dense, compacted ice stretch for hundreds of kilometers of the Andes mountain range in Chile and Argentina. The two lobes of the Patagonian icefields—north and south—are what is left of a much more expansive ice sheet that reached its maximum size about 18,000 years ago. The modern icefields are just a fraction of their previous size, though they remain the southern hemisphere’s largest expanse of ice outside of Antarctica.
The northern icefield covers about 4,000 square kilometers and has 30 significant glaciers along its perimeter. In April 2017, Landsat 8 captured this rare cloud-free view of a portion of the icefield.
Ice creeps downslope through mountain val eys and exits through so-cal ed “outlet glaciers.” Many come to an abrupt end on land, while others terminate in water. The San Rafael and San Quintín glaciers (shown at the right) are the icefield’s largest. Both have been receding rapidly in the past 30 years.
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Manning Island and Foxe Basin
Canada
Although it may look like a microscope’s view of a thin slice of mineral-speckled rock, this image was actual y acquired in
space by the Earth Observing-1 satel ite in July 2012. It shows a small set of islands and a rich mixture of ice in Foxe Basin, the shal ow northern reaches of Hudson Bay.
The small and diverse sizes of the ice floes indicate that they were melting. The darkest colors in the image are open water.
Snow-free ice appears gray, while snow-covered ice appears white. The smal , dark features on many of the floes are likely melt ponds.
Foxe Basin sea ice is known for having an unusual brown color due to staining from sediment from rivers. Also, the basin is shal ow enough that it is often rich with marine sediments kicked up from the bay floor. The Manning Islands stand to the lower left, beneath the bright white wedge.
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Ice Water
United States
As temperatures rise in the summer, turquoise splotches of color begin to speckle the icy surfaces of the Arctic. Those splashes of blue are melt ponds—areas where snow has melted and pooled in low spots atop glaciers and sea ice. During an airborne research campaign in July 2014, a scientist shot this photograph while flying over a glacier in southeastern Alaska. Chunks of ice float on the pond’s turquoise water.
Many questions remain about the impact of melt ponds on the Arctic. Compared to bright white snow and ice, liquid water absorbs much more heat from sunlight. So when a pool of water forms on top of ice, it changes the heat balance. The water warms in the sunlight and can speed the melting of surrounding ice, influencing the overall melting and movement of ice sheets and sea ice.
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