GeoLog

imaggeo on mondays

Imaggeo on Mondays: Inside the whale’s mouth

Imaggeo on Mondays: Inside the whale’s mouth

Often there are moments in our lives when we are reminded of the strength and magnitude of our environment, whether that’s trekking through a mountain range or gazing at the horizon from the ocean shore. Yet arguably there are few things that can make you feel as small as a particularly powerful summer storm.

“The atmosphere is undoubtedly one of the most dynamic components in the Earth System. Nothing can demonstrate the power of nature to an observer as well as a strong thunderstorm rolling in,” said Michiel Baatsen, a climate researcher at Utrecht University in the Netherlands who snapped this week’s featured photo. Besides being a climate researcher, Baatsen is also a weather enthusiast and storm chaser, fascinated by severe weather and thick towering cloud formations.

He and a team of friends will often hit the road, travelling across Western Europe in pursuit of extreme thunderstorms that pass the continent. “In these ventures, we try to capture some inspiring scenes and have been amazed many times by the things we end up seeing,” said Baatsen.

This photo was taken in June last year while Baatsen was traveling through the northeastern corner of the Netherlands. He and his friends were searching for a thunderstorm that had crossed the border from Germany, but the local humidity was relatively high, making visibility too poor to properly locate the approaching storm. “After several failed attempts to locate the approaching storms, we realised the conditions were so hazy that they completely obscured the leading cloud structures,” said Baatsen. But once the first clouds passed overhead, the conditions suddenly changed and the sky became clearer, revealing a dramatic view of the storm.

If you feel as if the storm feature in the photo is about to engulf you, you’re not alone. This kind of cloud structure is called a shelf cloud, but it’s also often referred to as a ‘whale’s mouth’, since the formations often give the impression of being consumed by a giant whale.

‘Whale’s mouth’ clouds take shape when cold, dense air surging out of a thunderstorm collides with warm air entering the storm. When the two currents make contact, the air goes upward and condenses into a thick sheet of clouds. This kind of formation appears at the leading edge of a thunderstorm, a harbinger to the incoming rainfall.

For Baatsen and his colleagues, the storm offered a short window between its first gusts and the subsequent rainfall, allowing them to observe this natural phenomenon. “With the whale’s mouth being overhead, there was a brief moment to appreciate this scene during which one was basically trapped in a cage surrounded by the rain rolling in on one side and the haze drawing away on the other side,” said Baatsen.

By Olivia Trani, EGU Communications Officer

Imaggeo on Mondays: The ephemeral salt crystals

Imaggeo on Mondays: The ephemeral salt crystals

Rock salt stalactites (Speleothems) are the indicators of entrance in a salt cave. These crystal stalactites precipitate from brine only at the entrance in the salt caves, as that is the only place where the physical and chemical properties of the air and the brine dripping from the ceiling allow these crystals to grow and be preserved. And they are extremely fragile – if there is just a small change in the brine’s chemistry or the air’s moisture, the crystals will vanish away, dissolved in a pool of brine or a stream of salt water flowing out of the cave. These stalactites of salt crystals are what we call secondary salt; that means the original salt (formed million years ago) dissolved in water and re-precipitated recently.

Yes, you heard right, the sediments that contain these caves are made of rock-salt in the ground. Actually, caves can be formed in various types of soluble materials, from limestone and gypsum to halite (rock salt) or even ice. The salt caves denote the presence of salt near the surface of the earth.

How does the salt get there? Well we do know that there have been moments in the history of the Earth when certain seas (salt giants) have accumulated enormous deposits of salt instead of the more familiar mud sediments. However, we still don’t completely understand the process. That is also due to the fact that, unlike other rocks, salt has a plastic behavior, it tends to ‘flow’ upwards through other rocks, towards the surface (pretty much like wet sand between your feet when at seaside). As salt squeezes its way up, it deforms the rocks around it and creates salt domes that are later dissolved by water. This dynamic behavior of salt means that there are very few places where we can find salt in its original location and the understanding of the natural mechanisms that form salt remains incomplete.

Earth scientists like me, try to understand the mechanism of salt formation. Because the big picture of the past environments where salt is formed is currently blurred, we try to recreate a ‘movie’ of the past, that starts long before the formation of salts and ends long after. In this ‘movie’ we look at the past geography (paleogeography) and past environment (paleoenvironmental) changes from before to after the formation of the salts in order to single out key patterns that can bring us closer to removing the blur from this interesting episode in the story of oceans and seas.

I took this photo while doing field work in eastern Romania. The photo was taken on a tributary of the ‘Slănicul de Buzău’ river in the Buzău Land Geopark, an area of outstanding geological beauty, in the outer hills of South-East Carpathians. When I was stumbling on the salt caves in the field, I had to put mapping and sample collecting on pause. The layers of rock I was following had disappeared, replaced by a chaotic pile of mud, salt and small rock fragments. All I could do was check these rock fragments scattered in the landscape, try to figure out from where they come from, what layers of rock  the salt destroyed and of course, enjoy the geometric beauty of the ephemeral crystals.

By Dan V. Palcu, postdoctoral researcher at the University of São Paulo, Brazil

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: Monitoring Antarctica’s ocean current

Imaggeo on Mondays: Monitoring Antarctica’s ocean current

This week’s featured image depicts a quiet and still oceanic landscape in Antarctica, but polar scientists are studying how energetic and variable the ocean currents in this part of the world can be.

In this picture, the marine research vessel RRS James Clark Ross is making its way through the Lemaire Channel, a small passage off the coast of the Antarctic Peninsula, south of the southernmost tip of Chile. This channel is about 11 kilometres long and just 1,600 metres wide at its narrowest point, bordered by a spectacular range of steep cliffs.

At the time this photo was taken, the ship was headed to the Rothera Research Station, a British Antarctic Survey base on the white continent’s peninsula. The scientists aboard the vessel are part of a decades-long research campaign surveying the ocean current surrounding Antarctica, known as the Antarctic Circumpolar Current (ACC). The ACC is the world’s strongest and most influential current, transporting 165 million to 182 million cubic metres of water every second and connecting most of Earth’s major oceans. As such, any changes to the ACC have the potential to impact other marine environments around the world.

For more than 25 years, scientists from the UK’s National Oceanography Centre (NOC) have ventured south each Antarctic summer to measure the ocean’s physical features in one region of the Southern Ocean, called the Drake Passage. Spanning just 800 kilometres between the Falkland Islands and the Antarctic Peninsula, the Drake Passage is the shortest crossing from Antarctica to any other landmass. This makes it a prime spot to survey the ocean’s currents, as the flow is constricted to a narrow geographical region.

So far, researchers have completed 24 survey trips across the passage. The data collected during these trips have been used to assess how physical features of the ACC change, both throughout a single year and over the course of several years. Yvonne Firing at NOC leads the latest expeditions as part of the UK funded ORCHESTRA project. The continuation of this monitoring is helping scientists study how the ocean stores excess heat and carbon. No other ocean basin has been monitored so consistently, making the Drake Passage the most comprehensively studied part of the Southern Ocean.

By Olivia Trani, EGU Communications Officer

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: At the edge of a wildfire

Imaggeo on Mondays: At the edge of a wildfire

The Carpenter 1 fire burned approximately 11,000 ha in the Spring Mountain National Recreation Area (Humboldt-Toiyabe National Forest) near Las Vegas, Nevada between July 1, 2013 and its containment on August 18, 2013. The left side of the photo shows the fire affected arid desert scrub ecosystems at 1500 m (foreground) to subalpine pine ecosystems at 3400 m (background). The foreground of the photo clearly shows the lower-elevation boundary of the burned area, where low-severity fire burned off brush vegetation and Joshua trees.

Description by Teamrat Ghezzehei, as it first appeared on imaggeo.egu.eu.

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/.