GeoLog

Imaggeo

Imaggeo on Mondays: Isolated atoll

Imaggeo on Mondays: Isolated atoll

Covering a total area of 298 km², the idylic natural atolls and reefs of the Maldives stretch across the Indian Ocean. The tropical nation is famous for it’s crystal clear waters and picture perfect white sand beaches, but how did the 26 ring-shaped atolls and over 1000 coral islands form?

Coral reefs commonly form immediately around an island, creating a fringe which projects seawards from the shore. If the island is of volcaninc origin and slowly subsides below sea level, while the coral continues to grow growing outwards and upwards, an atoll is formed. They are usually roughly circular in shape and have a central lagoon. If the coral reef grows high enough, it will emerge from the sea waters and start to form a  tiny island.

“I took this photo while flying over the Maldives, south of Malè, from a small seaplane,” describes Favaro, who took this stunning aerial image of an atoll above the Indian Ocean.

Pictured, goes on to explain Favaro,

“[is] part of the ring-shaped coral reef bounding the atoll. On the right side of the image there is the lagoon and on the left side the open ocean. The coral reef is interrupted twice by ‘Kandu’ (water passages in Dhivehi [the language spoken in the Maldives]), which are the places where water flows in and out of the atoll when the tides changes”.

Two small harbours and antennas suggest the two small islands are occupied by local people, not by a resort or hotels.

“What always strikes me is how they can live so isolated, in a place which doesn’t offer basic resources, such as drinkable water,” says Favaro.

Fresh water is scarce in this archipelago nation. Rainwater harvesting is unreliable; poor rainfall means depleted collection tanks and groundwater tables. The problem is being exacerbated by climate change which is altering the monsoon cycle and rainfall patters over the Indian Ocean. As a result, the country relies heavily on desalination plants (and imported bottled water) to sustain the nation and the 1 million tourists who visit annually.

This animation shows the dynamic process of how a coral atoll forms. Corals (represented in tan and purple) begin to settle and grow around an oceanic island forming a fringing reef. It can take as long as 10,000 years for a fringing reef to form. Over the next 100,000 years, if conditions are favorable, the reef will continue to expand. As the reef expands, the interior island usually begins to subside and the fringing reef turns into a barrier reef. When the island completely subsides beneath the water leaving a ring of growing coral with an open lagoon in its center, it is called an atoll. The process of atoll formation may take as long as 30,000,000 years to occur. Caption and figure credit: National Oceanographic and Atmospheric Administration (NOAA).

References and further reading

How Do Coral Reefs Form? An educational resource by NOAA

Amazing atolls of the Maldives – a feature on NASA’s Earth Observatory.

 

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.

 

Imaggeo on Mondays: Low tide at Alexandra Fjord

Imaggeo on Mondays: Low tide at Alexandra Fjord

Today’s post takes us to the far northern reaches of our planet, to a desert like nothing you’ve seen before.

This picture is a view to the north across Alexandra Fjord, on the east coast of Ellesmere Island, in the Canadian High Arctic, with Sphynx island in the middle of the fjord. The south shore of Alexandra Fjord includes a polar oasis, an area of tundra vegetation and relatively mild climatic conditions normally found hundreds of kilometres further south. The oasis is surrounded by glaciers and icefields to the south, and polar desert on mountains to the east and west. Polar deserts can also be seen on the far shore in this picture; another scientist working in this area once described to me the ease of “doing geology” from the air due to the lack of plant or developed soil cover on much of the landscape.

The tundra ecosystems of the valley produce and consume greenhouse gases carbon dioxide, methane, and nitrous oxide because of the actions of soil dwelling microorganisms. The surrounding deserts appear nearly lifeless, with only scattered plants sheltered from the harsh winds on barren, rocky ground. Nonetheless, on a per-area basis these deserts contribute nearly as much to greenhouse gas processes as the oasis ecosystems, particularly nitrous oxide.

The surface of Alexandra Fjord freezes completely each winter, to a depth sufficient to support the weight of small aircraft. Researchers visiting this area in April and May land and take off from the ice, but we arrived in late June and used the raised beach cresh that sits some 100 metres inland as our runway. As the 24-hour daylight of summer warms the land and the sea, the ice breaks up and is flushed out towards the Davis Straight to the east. Small pieces of pack ice and small icebergs frequently ground on the shore of the fjord at each low tide, creating a stark and beautiful landscape of ice, land, and water that is best viewed at a distance due to the tendency of polar bears to wander along the shoreline in search of seals and other food.

By Martin Brummell, University of Waterloo, Ontario, Canada

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.

 

Imaggeo on Mondays: A total eclipse of the Moon

Imaggeo on Mondays: A total eclipse of the Moon

Today, all eyes are turned to the sky; at least in North America, where the region will be treated to an eclipse of the sun. The online hype is hard to miss and its hardly surprising, opportunities to see the moon completely cover the Sun, where you are, are rare*. According to NASA, the same spot on Earth only gets to see a solar eclipse for a few minutes about every 375 years!

If like us, you can’t be in North America to see the phenomenon, don’t worry, you can follow all the action on NASA’s live stream. Keep an on eye on social media channels too. Following the #Eclipse2017 and #Eclipse hashtags throughout the evening will no doubt allow you to see stunning photographs and video!

Instead of highlighting an image of a past solar eclipse, we thought we’d turn our attention to a total lunar eclipse instead.

The phenomenon is rarer than total solar eclipses and occurs when the Moon passes directly behind the Earth, so that the Earth cast’s a shadow over the Moon. Lunar eclipses happen only when the Sun, Earth and Moon are perfectly aligned.

Often during a lunar eclipse, the Moon will have a red/orange hue, as in today’s featured image. This happens because the Earth’s atmosphere absorbs some colours, as it bends sunlight towards the Moon.

Unlike solar eclipses, which are rather limited in their geographical extent, lunar eclipses are visible to all those on the dark side of the Earth (so all those experiencing night time), meaning half of planet Earth will see a lunar eclipse at any one time.

The next total Lunar eclipse will take place on 31st  January2018 and will be visible (at least to some extent) in North/East Europe, Asia, Australia, North/East Africa, North America, North/West South America, Pacific, Atlantic, Indian Ocean, Arctic, Antarctica. The other half of the globe will have to wait until 27th/28th July (2018) to catch a glimpse of a lunar eclipse.

*Editor’s Note: Contrary to popular belief, solar eclipses aren’t so rare. A total solar eclipse happens, on average, once every 18 months. What isn’t so common is it happening in a place near you. The science behind that is clearly explained in a recent post on Space.com.

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.

 

Imaggeo on Mondays: Symbiosis of ice and water

Imaggeo on Mondays: Symbiosis of ice and water

This mesmerising photograph is another of the fabulous finalists (and winner) of the 2017 imaggeo photo contest. Imaggeo is the EGU’s open access image repository. It’s a great place to showcase your photographs; so whether you are stuck in the lab this summer, frantically typing away at a paper, or are lucky enough to be in the field, be sure to submit your photographs for all EGU members to see. You never know, we might choose to feature it on the blog too!

This picture was taken at Storforsen, an impressive rapid in the Pite River in northern Sweden. That day, the sinking sun illuminated the whole area with warm reddish colors which formed a contrast to the remains of the long-lasting winter period. The rapid is located close to the site of a temporary seismological recording station which is part of the international ScanArray project. Within that project we focus on mapping the crustal and mantle structure below Scandinavia using a dense temporary deployment of broadband seismometers.

By Michael Grund, Karlsruher Institut für Technologie (KIT)

Imaggeo is the EGU’s online open access geosciences image repository. All geoscientists (and others) can submit their photographs and videos to this repository and, since it is open access, these images can be used for free by scientists for their presentations or publications, by educators and the general public, and some images can even be used freely for commercial purposes. Photographers also retain full rights of use, as Imaggeo images are licensed and distributed by the EGU under a Creative Commons licence. Submit your photos at http://imaggeo.egu.eu/upload/.

 

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