GeoLog

Imaggeo on Mondays

Imaggeo on Mondays: One of the oldest evergreen rainforests in the world

Imaggeo on Mondays: One of the oldest evergreen rainforests in the world

A blazing sky and shimmers cast by water ripples frame the spectacular beauty of one of the world’s oldest treasures: an evergreen rainforest in Thailand. Today’s featured image was captured by Frederik Tack, of the Institute for Space Aeronomy in Brussels.

This picture was taken during sunset between the limestone mountains with the sunlight reflecting on beautiful Ratchaprapha lake in Khao Sok National Park.

Khao Sok National Park is one of the oldest evergreen rainforests in the world since Thailand has remained in a similar equatorial position throughout the last 160 million years. The climate in the area has been relatively unaffected by ice ages, as the landmass is relatively small and has seas on both sides. Even whilst other places on the planet were suffering droughts, the Khao Sok region still received enough rainfall to sustain the forest.

Khao Sok is also famous for its vertiginous limestone cliffs or ‘karst’ mountains. In most of the region, ground level is about 200m above sea level with the average mountain heights around 400m. The tallest peak in the National Park is 960m high. The national park area is inhabited by a large range of mammals such as tigers, elephants, tapirs and many monkey species. Birds such as hornbills, banded pittas and great argus are as well forest residents. Less commonly seen reptiles include the king cobra, reticulated python, and flying lizards.

One of the most interesting areas is stunningly beautiful Cheow Lan or Ratchaprapha Lake in the heart of the National Park. It is an 165-square-kilometre artificial lake, created in 1982, by the construction of Ratchaprapha Dam as a source of electricity.

By Frederik Tack, of the Institute for Space Aeronomy in Brussels

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: The unique bogs of Patagonia

Imaggeo on Mondays: The unique bogs of Patagonia

Patagonia, the region in southernmost tip of South America, is as diverse as it is vast. Divided by the Andes, the arid steppes, grasslands and deserts of Argentina give way to the temperate rainforests, fjords and glaciers of Chile. Also on the Chilean side are rolling hills and valleys of marshy topography: Patagonia’s bogs. Today, Klaus-Holger Knorr, a researcher at the University of Münster’s Institute for Landscape Ecology, tells us about what makes these peatlands so unique.

This picture shows an ombrotrophic, oceanic bog at the Seno Skyring Fjord, Patagonia, Chile. It is a view from the inner part of the peatland south toward the shore of the Fjord, in the background Isla Escapada and the Gran Campo ice field. Ombrotrophic bogs are peatlands (accumulations of more or less decomposed plant material which collect in a water-saturated environment) receiving their water and nutrients solely from the atmosphere, i.e. by rain, wet and dry deposition.

Similar to their Northern counterparts in Canada, Northern US, Fennoscandia or Siberia, these southern Patagonian peatlands  formed after the last deglaciation and accumulated huge amounts of carbon as peat.

Peatlands cover only about 3 % of the global land surface but store about a third of the soil carbon pool. Peat is formed primarily as there is excess rainfall, peat soils are water logged, oxygen gets depleted, and decomposition is limited. Pristine, undisturbed peatlands can store as much as 10-50 g carbon per square meter and year.

What makes the peatlands in Patagonia  particularly interesting  is their pristine, undisturbed conditions and extremely low input of nutrients from the atmosphere, compared to the high input into sites in densely settled or industrial regions. This allows studies of peatland functioning under natural conditions and absence of anthropogenic impacts.

Moreover, peatlands in Patagonia harbor a specific kind of vegetation, including cushion forming plants such as Astelia pumila and Donatia fascicularis. These cushion forming plants have a very low above ground biomass but an extremely large rooting system, reaching down to a depth of >2 m in case of A. pumila. As these roots act as conduits for oxygen to sustain viability of the roots in the water logged peat, they have been shown to aerate large parts even of the saturated zone, thereby impeding high methane production and emission. Oxygen supply by these roots is even hypothesized to stimulate peat decomposition and thereby lead to particularly decomposed peat under cushion plant cover.

Another plant species only occurring in peatlands of Southern Patagonia, a small conifer named Lepidothamnus fonkii, has developed a particular strategy to overcome nutrient deficiency: it has formed a close association with bacteria being able fix atmospheric nitrogen to fulfill the demand of nitrogen for growth. While such nitrogen fixation is well known for legumes and some tree species, it has rarely been found for conifers.

A further important factor for peatlands in Patagonia, leading to the term “oceanic bogs”, is the fact that these peatlands in close vicinity to the seashore receive high inputs of sea salts from sea spray, modifying availability of associated elements such as Sodium, Calcium, Magnesium, Sulphur and others.

By Klaus-Holger Knorr, researcher at the University of Münster’s Institute for Landscape Ecology

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: Measuring the wind direction

Imaggeo on Mondays: Measuring the wind direction

Remote, rugged, raw and beautiful beyond measure, the island of South Georgia rises from the wild waters of the South Atlantic, 1300 km south east of the Falkland Islands.

The Allardyce Range rises imposingly, south of Cumberland Bay, dominating the central part of the island. At its highest, it towers 2935 m (Mount Paget) above the surrounding landscape. In the region of 150 glaciers carve their way down the rocky peaks, toward craggy clifftops and the emerald green waters of the ocean.

Geologically speaking, the territory is unique. South Georgia sits atop the place where the South American Plate and the Scotia Plate slide past one another; exactly which can claim ownership of the mountainous outpost is highly debated.

As East and West Gondwana split, about 185 million years ago, South Georgia was pulled away from Tierra del Fuego, an archipelago off the southernmost tip of mainland South American, and experienced severe volcanism.

The island is so remote and exposed, it creates its own weather system. It sits in the path of very strong winds, the westerlies, which flow through the subtropical highs in the Southern Hemisphere.  As air flows over the high mountains of South Georgia, they generate atmospheric gravity waves (which transfer energy from the troposphere – the layer closest to the Earth’s surface – to the upper layers of the atmosphere, including the stratosphere, where the ozone layer is found). Atmospheric gravity waves are responsible for the transfer of considerable amounts of energy over large distances, and thus have a substantial impact on weather and climate.

It is precisely to study South Georgia’s atmospheric gravity waves that Andrew Moss, the author of today’s photograph, journeyed to the remote island back in January 2015 as part of the South Georgia Wave Experiment (SG-WEX). The project was led by the University of Bath, in collaboration with the British Antarctic Survey, the University of Leeds, and the UK Met Office. As part of this project Andrew worked with a colleague at the University of Bath (UK) to release radiosondes – a small, expendable instrument package that is suspended below balloon which measures pressure, temperature and humidity – to better understand the atmospheric conditions and measure atmospheric gravity-wave activity above the island.

The chilly, often cloudy and wet landscape is a wildlife haven. It is home to a staggering five million seals and 65 million seabirds.  The wildlife is so rich, on and off the island, that large swathes of South Atlantic waters surrounding South Georgia are protected and onshore activities which might disturb wildlife require permits.

“Over the course of the two-week field campaign, King Penguins, fur seals and elephant seals often surrounded us while we worked,” describes Andrew.  “During the trip, I captured a group of penguins, with their backs to the wind, clustered together on a windy day.”

References and further reading:

Imaggeo on Mondays: Atmospheric gravity waves (GeoLog, EGU Blogs, April 2017)

Hoffmann, L., Grimsdell, A. W., and Alexander, M. J.: Stratospheric gravity waves at Southern Hemisphere orographic hotspots: 2003–2014 AIRS/Aqua observations, Atmos. Chem. Phys., 16, 9381-9397, https://doi.org/10.5194/acp-16-9381-2016, 2016.

South Georgia & the South Sandwich Islands Government website

Radiosondes – a guide by the National Weather Service (NOAA)

Find out more about Andrew, here: https://www.researchgate.net/profile/Andrew_Moss8

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/.