Underwater structures of the Great Bahamas Bank are pictured in this image from the Landsat-8 satellite on 5 February.
Sitting north of Cuba, the bank is made of limestone – mainly from the skeletal fragments of marine organisms – that has been accumulating for over 100 million years.
Currents sculpted these underwater sediments into the wavy pattern we see along the bottom of the image, just a few meters deep.
We can clearly see where the shallow waters drop off into the deep, dark water of an area known as the Tongue of the Ocean. With depths of up to about 4000 m, this trench surrounded by islands, reefs and shoals has an opening to the Atlantic Ocean at its northern end (not pictured).
The trench was carved during the last Ice Age when the land was still above sea level and exposed to erosion from draining rainwater. As the Ice Age ended and the massive ice sheets across the globe melted, global sea levels rose and flooded the canyon.
Over the deep Tongue we can see a few sparse clouds.
This image, featured in the Earth from Space video program, is ESA’s 500 Earth Observation Image of the Week. The first of the series, published in 2004, also featured the colorful waters of the Bahamas, as seen by the Envisat satellite.
Image credit: USGS/ESA
Northern Somalia’s Cal Madow mountain range is pictured in this image from Japan’s ALOS satellite.
In contrast to the sparsely-vegetated majority of the country – typical of its semi-arid to arid climate – the mountain range is densely forested. In this image, the vegetated areas appear much darker.
The ecologically diverse region is home to a number of endemic plants species, as well as many rare animals. Unfortunately, the area lacks proper conservation and is threatened by deforestation and intensive livestock grazing.
The uplifted plateau to the south has the distinct pattern of water erosion from rivers and streams making their way towards the edges of the cliffs, before cascading down. There are numerous perennial and persistent waterfalls in this region.
In some areas, we can see where water continues to flow north across the coastal plain towards the Gulf of Aden (not pictured).
The Japanese Advanced Land Observation Satellite captured this image on 2 January 2011. ALOS was supported as a Third Party Mission, which means that ESA used its multi-mission ground systems to acquire, process, distribute and archive data from the satellite to its user community.
In April 2011 the satellite abruptly lost power while mapping Japan’s tsunami-hit coastline.
This image is featured on the Earth from Space video program.
Image credit: JAXA/ESA
A giant, geological wonder in the Sahara Desert of Mauritania is pictured in this satellite image.
The 40 km-diameter circular Richat structure is one of the geological features that is easier to observe from space than from down on the ground, and has been a familiar landmark to astronauts since the earliest missions.
Once thought to be the result of a meteor impact, researchers now believe it was caused by a large dome of molten rock uplifting and, once at the surface, being shaped by wind and water into what we see today. Concentric bands of resistant quartzite rocks form ridges, with valleys of less-resistant rock between them.
The dark area on the left is part of the Adrar plateau of sedimentary rock standing some 200 m above the surrounding desert sands. A large area covered by sand dunes – called an erg – can be seen in the lower-right part of the image, and sand is encroaching into the structure’s southern side.
Zooming in on the southern side of the bullseye, we can see individual trees and bushes as tiny dots. These follow a river-like structure that appears to have been dry when this image was acquired, a few weeks after the rainy season. Some areas to the south and east of the Richat appear to be covered with temporary lakes, which are dry for most of the year.
This image, also featured on the Earth from Space video program, was acquired on 23 November 2010 by the Advanced Visible and Near Infrared Radiometer on Japan’s ALOS satellite.
Image credit: JAXA/ESA
The Grand Canyon in northern Arizona is a favorite for astronauts shooting photos from the International Space Station, as well as one of the best-known tourist attractions in the world. The steep walls of the Colorado River canyon and its many side canyons make an intricate landscape that contrasts with the dark green, forested plateau to the north and south.
The Colorado River has done all the erosional work of carving away cubic kilometers of rock in a geologically short period of time. Visible as a darker line snaking along the bottom of the canyon, the river lies at an altitude of 715 meters (2,345 feet), thousands of meters below the North and South Rims. Temperatures are furnace-like on the river banks in the summer. But Grand Canyon Village, the classic outlook point for visitors, enjoys a milder climate at an altitude of 2,100 meters (6,890 feet).
The Grand Canyon has become a geologic icon — a place where you can almost sense the invisible tectonic forces within the Earth. The North and South Rims are part of the Kaibab Plateau, a gentle tectonic swell in the landscape. The uplift of the plateau had two pronounced effects on the landscape that show up in this image. First, in drier parts of the world, forests usually indicate higher places; higher altitudes are cooler and wetter, conditions that allow trees to grow. The other geologic lesson on view is the canyon itself. Geologists now know that a river can cut a canyon only if the Earth surface rises vertically. If such uplift is not rapid, a river can maintain its course by eroding huge quantities of rock and forming a canyon.
This astronaut photograph (ISS039-E-5258) was taken on March 25, 2014 by the Expedition 39 crew, with a Nikon D3S digital camera using a 180 millimeter lens, and is provided by the ISS Crew Earth Observations Facility and the Earth Science and Remote Sensing Unit, Johnson Space Center. It has been cropped and enhanced to improve contrast, and lens artifacts have been removed.
Image credit: NASA
This satellite image was acquired over the edge of a salt marsh near the northeast Caspian Sea in southwestern Kazakhstan.
The Caspian Sea (not pictured) is the largest inland body of water by surface area. With an average depth of about 5 m, the northern part of the Caspian is very shallow, while the central and southern parts of the sea are much deeper. The salinity of the waters also change from north to south, being more saline in the northern, shallow waters and less in the south.
The salt marsh in the upper section of this image was once a gulf of the Caspian Sea, but fluctuating sea levels over the last decades cause it to be cut off occasionally from the main body of water and even dry up. In this image, it appears that the water has evaporated, leaving behind a white salt crust.
Rock formations dominate the central part of the image, while a plateau stretches south and east (not pictured). The visible shapes in combination with the dark color of the rocks may indicate that they are volcanic, with water erosion evident in the finger-like runoff patterns.
The grey rim between the land and salt pan comes from the sedimentary runoff from the land mixing with the saltwater. When the marsh is dry, a greyish color is left behind.
The arid climate in this region makes it easy to acquire optical imagery from satellites, without the obstruction of visibility by clouds.
This image was acquired on 6 November 2012 by the Korea Aerospace Research Institute’s Kompsat-2 satellite and is featured on the Earth from Space video program.
Photo credit: KARI/ESA
This image from Japan’s ALOS satellite shows part of the Flinders Ranges in South Australia, about 500 km north of Adelaide.
The area pictured is between Flinders Ranges National Park to the south, Vulkathunha-Gammon Ranges National Park to the north and Lake Frome due east (none of which is pictured).
The curving structures that dominate this image are part of a larger geosyncline – a subsiding linear trough in Earth’s crust – that includes the Flinders Ranges. The geosyncline consists of sedimentary rocks in a basin that were folded about 500 million years ago and have been eroded to the current landscape. In this image, the different colors show the different layers of rock.
Some of the oldest fossilised animal life have been found in parts of the Flinders Ranges.
Running up the middle of this image is a long, narrow gorge – typical of the ranges.
Along the right side of the image, the terrain is flat with a long, straight road running north–south. Numerous creeks appear like veins across the entire image.
The Flinders Ranges is one of Australia’s most seismically active regions, with numerous small earthquakes recorded every year.
Japan’s Advanced Land Observation Satellite captured this image on 3 January 2009. ALOS was supported as a Third Party Mission, which means that ESA used its multi-mission ground systems to acquire, process, distribute and archive data from the satellite to its user community.
This image is featured on the Earth from Space video program.
Image credit: JAXA/ESA
This image from Japan’s ALOS satellite shows the Aorounga Crater in northern Chad.
The crater is just south of the Tibesti Mountains, a range of inactive – with some potentially active – volcanoes in the central Sahara desert.
Measuring about 12 km across, the crater was created by a meteorite impact about 340 million years ago.
Clearly visible is the dark, central peak, caused by material splashing up after the impact, similar to how water bounces back up when a stone is thrown in. This peak is surrounded by a low, sand-filled ring, which is surrounded by another ring of rock from when the material was thrown outwards. A distinctive low, sand-filled trough circles the others – the outer edges of the initial impact.
The linear rock ridges that run diagonally across this image are ‘yardangs’ and are formed by wind erosion. Here, we can clearly see how the wind blows from northeast to southwest. Sand dunes form in the wind-cut valleys between the rock ridges of the yardangs.
Japan’s Advanced Land Observation Satellite captured this image on 3 November 2010. ALOS was supported as a Third Party Mission, which means that ESA used its multimission ground systems to acquire, process, distribute and archive data from the satellite to its user community.
This image is featured on the Earth from Space video program.
Photo credit: JAXA/ESA
