Earth Matters

Walking on Venezuela’s Last Glacier

September 27th, 2018 by Kathryn Hansen

The retreat of Humboldt Glacier—Venezuela’s last patch of perennial ice—means that the country could soon be glacier-free. We featured the glacier in August 2018 as an Image of the Day showing how it changed between 1988 and 2015.

Satellite images can tell you a lot about a glacier, but direct measurements by people on the ground provide a unique, important perspective, especially for glaciers as small as Humboldt. Carsten Braun, a scientist at Westfield State University, last surveyed the glacier in 2015. He talked about what it was like to stand on Venezuela’s last glacier.

The Operational Land Imager (OLI) on Landsat 8 acquired this natural-color image of the glacier on January 6, 2015.

These photographs show the ground-based view of Humboldt Glacier in 2015. Photos by Carsten Braun.

What things were you measuring during the 2015 survey?

This was a very ‘low-tech’ trip: just me and a guide. The approach to the glacier takes two days of very rough hiking with big packs. That gets you to base camp at Laguna Verde below the glacier.

To get to the glacier takes another three hours on rough terrain. This is definitely popular with climbers. They cross the Humboldt Glacier and then summit Pico Humboldt.

I did the same thing in 2009 and 2011: I walked around the glacier right on the margin with a simple GPS receiver to make a map of it. That sounds a lot easier than it is. Walking right on the edge of a glacier can be difficult and dangerous. This was definitely both!

What was the ice like? Parts of it look like snow or slush.

This glacier is little different than what you may have experienced. It is tiny and does not have an accumulation area. The surface is 100 percent ice everywhere, just covered in some parts in wet seasonal snow that will melt away. Basically that means that the Humboldt Glacier has no means to ‘add’ mass (‘eat’) and continuously loses mass everywhere (‘fasting’). Obviously, that’s not sustainable.


Photos by Carsten Braun.

Do you remember what you were thinking while hiking on the country’s last glacier?

I was definitely considering the impacts of losing this glacier. It has little ‘practical use’ today, as it is so small and pretty much irrelevant for water supply. Its disappearance would not impact water resources much, if at all. That’s much in contrast with countries like Peru and Bolivia, where glacier recession already creates huge problems for water resources, hydro-power, etc.

The impact in Venezuela is more at a spiritual level. The mountain chain is was named Sierra Nevada de Mérida (snowy mountain range of Mérida) because of its glacier cover. Now it will be gone soon and may never come back again. (Well, that’s up to us humans to decide.) And with that, the reality of these mountains will change. The lack of glaciers will be the ‘new normal.’ It’s a little bit like losing a species: once it’s gone, you never realize that it is missing.


Mississippi’s Pulliam Prairie

June 21st, 2018 by Kathryn Hansen

Photo by JoVonn Hill, Mississippi State University.

NASA Earth Observatory images by Joshua Stevens.

This month we published a satellite image and map of the southern United States featuring the Black Belt Prairie—a crescent-shaped swath of land running through Mississippi and Alabama named for its characteristically dark, fertile soil. Most of the fertile soils are cultivated, contrasting sharply with adjacent forested areas.

Grassland expert JoVonn Hill of Mississippi State University noted that in the 1830s, the Black Belt contained about 356,000 acres of prairie. Today, less than 1 percent of prairie land remains. One such prairie remnant is the Pulliam Prairie in Chickasaw County, Mississippi. Hill snapped this photograph (top image) of native grassland within the Pulliam Prairie, which in total spans about 250 acres. That’s a decent size for Black Belt prairie remnants, most of which span just 5-20 acres.

Pulliam Prairie is one of the most significant prairie remnants in Mississippi, given its large area and the diversity of species found there. Black Belt prairie remnants dot the landscape in Alabama too, all of which are important sites for the supporting an array of native vegetation and habitat. As Hill noted in our initial story about the region: “Find a remnant of the Black Belt prairie, and you could see some of its unique grassland birds; more than 200 species of plants, 1,000 species of moths, 107 species of bees, 33 species of grasshoppers, and 53 species of ants.”

Ground to Space: Yaguas National Park

May 8th, 2018 by Kathryn Hansen

In January 2018, Peru’s protected area grew by more than 2 million acres with the creation of Yaguas National Park. The forest is largely intact, unbroken by roads and human activity. Only the Yaguas River cuts through the continuous canopy, visible in this image acquired by Landsat 8 in August 2017.

Scientists from the Field Museum got an even closer look at the forest when they flew over it before it was designated a national park. “When you see it from the air, it appears to stretch to the horizon,” said Corine Vriesendorp, a conservation ecologist at the Field, in a story about the new park. The following photographs by Álvaro del Campo offer this aerial perspective.

The first photo shows an area of intact forest inside Yaguas National Park. Expanses like this one are important for the diversity of the region’s plants and animals.

The park preserves more than forest; it protects an entire watershed. A segment of the Yaguas River is visible in the the second photograph. According to an inventory conducted by the Field Museum in 2010, the diversity of fish in this river could be the highest in Peru. Over the span of three weeks, experts counted 337 species of fish.

In the satellite image at the top of this page, notice the yellow areas on either side of the river that appear to be bare. These are actually peatlands: grounds rich with a soil-like mixture of partly decayed plant material that can build up in the abandoned river meanders. The photograph above provides an aerial view of peatlands.

“Ten years ago, we were just beginning to realize that there were important peat deposits in the Peruvian Amazon,” Vriesendorp said in a March 2018 Image of the Day. “Although there has been no comprehensive mapping of the Putumayo’s peatlands to date, it is likely that the below-ground carbon stock is immense.”

Ground to Space: Iguazú Falls

November 29th, 2017 by Kathryn Hansen

In 2016, we published space-based imagery of Iguazú Falls—South America’s famous system of waterfalls, which is near a bend in the Iguazú River between Argentina and Brazil. Spray from the falls reaches so high that it is visible from space. A crew member aboard the International Space Station captured the photograph above on May 24, 2016.

The view from the ground is also quite compelling, attracting more than a million visitors per year. The images below show ground-based views of the falls, photographed photographed by NASA’s Alexey Chibisov from the Argentine side of the river on November 28, 2017. Chibisov took the photos while on vacation after weeks in the field with the Operation IceBridge mission.

Photo by Alexey Chibisov.

Lush, subtropical rainforest surrounds the falls. The vegetation here is part of a remaining fragment of the Atlantic Forest, which stretches from the east coast of South America inland toward the Amazon. The forest is habitat for tens of thousands of plant species and thousands of animal species.

Photo by Alexey Chibisov.

Sediment carried by the fast-moving river can impart a red-brown color to the water, especially after periods of heavy rain.

Photo by Alexey Chibisov.

The mist is the result of water that plunges as much as 260 feet (80 meters) over layers of basalt cliffs.

Photo courtesy of Luciano Javier Avila.

Dozens of wildfires blazed along the Atlantic coast of Argentina coast last winter. One of them left behind a massive burn scar near the Valdez Peninsula. When we wrote about the fires last month, we were unable to say with certainty whether the plume rising off the burn scar was airborne ash or dust. A quick recap from our article:

This part of Argentina’s coast is sparsely populated, arid, and covered in scrubby undergrowth. The closest city is Puerto Madryn, more than 30 kilometers (20 miles) from the burn scar. Due to this remoteness, it is difficult to verify the composition of plumes.

At the time, Santiago Gassó, a NASA scientist who studies the global transport of ash and dust, gave us his best guess:

While Gassó believes ash caused this plume, it is possible that finely ground rock and soil dust also could have become dislodged by the fire. Vegetation and roots (which usually hold the soil in place) would have been removed by the fire, making it easier for the strong regional winds to sweep dust off of the land.

Since then, a reader has written to us with more details. Luciano Javier Avila, a biologist with the Patagonian Institute for the Study of Continental Ecosystems, walked around the site just days after the fires and took photos of the burned area. He confirmed that the cloud was, in fact, dust. Strong winds in January and February caused dust plumes visible from Madryn.

The fire highlights the importance of plants in this semi-arid region, according to Avila. Many of the plants which used to grow here are larrea (“jarilla” in Spanish), a desert shrub that flowers in yellow. Without their roots holding the soil together, the wind was able to blow large amounts of fine dust into the air.

Watch out, master gardeners: There’s competition up above.

Scientists have made marked developments in growing vegetables in space this spring. Researchers based at Kennedy Space Center have been working with a team from the University of Arizona to create a prototype lunar/Mars greenhouse. The cylindrical, inflatable chamber measures 18 feet long and 8 feet in diameter. It recycles waste and water from astronauts, and uses carbon dioxide they exhale.

Growing edible plants in space will allow humans to venture farther beyond our home planet, said Ray Wheeler, lead scientist for Kennedy Advanced Life Support Research. “The greenhouses provide a more autonomous approach to long-term exploration on the Moon, Mars and beyond,” he said.

Image by University of Arizona.

In other space veggie tales…

Last month, perhaps the most-watched cabbage in the world—technically speaking, in Earth orbit—sprouted. Two tiny shoots of the Tokyo Bekana Chinese cabbage poked out of their specially-designed plant pillow. The pillow acts like a miniature plant bed, providing nutrients without the mess of dirt careening through space.

The cabbage is but the most recent crop on the ISS. The crew’s first harvest of space veggies from the Veg-01 experiment took place in 2015. However, flower-raising efforts have encountered a few more obstacles, including the formation of mold.

Scott Kelly with romaine lettuce. Image by NASA.

To learn more, check out this video, aptly titled “Lettuce Look at Veggie”:

Petermann Glacier’s New Crack

April 24th, 2017 by Kathryn Hansen

In early April, remote sensing scientist Stef Lhermitte examined Sentinel-2 satellite images and saw a new crack developing on Greenland’s Petermann Glacier. About two weeks later, Landsat 8 also got a look (top image). Read more about that image here.

But the space-based view is not the only evidence of a new crack in the large glacier. NASA’s Operation IceBridge has been making science flights in the area this month, and scientists got a first-hand look. Kelly Brunt, a glaciologist at NASA’s Goddard Space Flight Center, snapped the photograph above from a window of a P-3 Orion research plane on April 14. The new crack is the feature running diagonal from the bottom-left of the photo toward the center.

“What’s interesting here is that the crack originated in the center of the glacier, not along the edges,” Brunt said. “When John Sonntag and I were looking for the new crack during the flight, we were looking for something substantial emanating from the edge. This totally surprised me!”

Most cracks start along a glacier’s edge, where a huge amount of strain is produced as the glacier slides along the walls of a fjord. That is especially true for Petermann—a narrow glacier that has previously rifted along the edges of its floating shelf.

Cracks that make their way across an ice shelf can eventually release icebergs. Petermann has launched two huge icebergs since 2010, so scientists are watching for additional retreat. It remains to be seen whether this crack will result in an iceberg. If the crack continues to lengthen, it could potentially meet the older rift at the edge of the glacier, visible near the top-center of the photo.

View more images of the rift and other icy phenomenon here.

Hunting “Peak Bloom” in a California Desert

April 3rd, 2017 by Kathryn Hansen

Photo by Ray Boren.

In late March 2017, California’s Colorado Desert sprang to life with vegetation following a period of ample precipitation. From space, imagery acquired on March 23 showed a widespread green up. From the ground, photographs from the same area showed the greenery topped with vibrant blooms.

Writer and avid amateur photographer Ray Boren was on location in Anza-Borrego Desert State Park to witness peak bloom, but not without a little trial and error in timing. He shared some photographs and a brief description of his journey.

“I first visited Anza-Borrego last year, in early May—a little late, I discovered, to catch the blossoms at their peak (though there were a few even then). It was already hitting 100 degrees there ….

So, when I heard that this year’s “super-bloom” in California’s largest state park was even better—enhanced by drought-busting winter and spring moisture—I had to dash the 800 or so miles from my Utah home to see what I could see. I did so with my sister Elaine, and we were well rewarded.

These photographs are from a drive through Anza-Borrego on a beautiful, even “cool” Monday, March 27, 2017.

The vista (top photo) is from Anza-Borrego’s granite mountains, which basically form a north-south spine through the huge state park. The view is from a turnoff on S22, a San Diego County road toward the park’s north side, and is looking east. From this point, you can look down upon the community of Borrego Springs, which is where Anza-Borrego’s visitor center is located (and which is quite recognizable in the satellite photos NASA Earth Observatory used as an Image of the Day).

The yellow flowers, which blanket the sunny slopes, are I believe California trixis. Gangly, multi-limbed ocotillo, with their flowering red tips, are common in the park, and they are having a grand spring.”

Photo by Ray Boren.


Photo by Ray Boren.

“Pictured in other photos, from the same S22 route, are beavertail cactuses, with their brilliant pink-lavender flowers just beginning to pop. The super-bloom seems most dominant on the north side of the park (we also drove south, to see the badlands). The garden at the visitor center is bursting with color, including such lovely plants as wolf’s cholla, barrel cactus and California’s squat but beautiful fan palms. We even saw a couple of Anza-Borrego’s iconic Peninsular desert sheep (“borrego”) on the ridges.

During our journey, we also saw desert flowers near the border with Nevada and Arizona, and were amazed by the bountiful show under way at the Antelope Valley California Poppy Reserve near Lancaster, which we visited on the way home.”

The Anza-Borrego Desert without wildflowers blooming. This image was acquired by the Operational Land Imager (OLI) on Landsat 8 on March 20, 2016. Learn more.


The Anza-Borrego Desert during a wildflower bloom. Notice the greens and purples around Borrego Springs.  This image was acquired by the Operational Land Imager (OLI) on Landsat 8 on March 23, 2017. Learn more.

Egypt’s Greening Desert

March 29th, 2017 by Kathryn Hansen

NASA Earth Observatory image by Joshua Stevens, using Landsat data from the U.S. Geological Survey.


Cultivated desert. Photo by Ragab Hafiez.

In early March 2017, we featured the top image as our monthly satellite puzzler and as an Image of the Day. But sometimes we learn even more about an image after we publish, as people write to us with a local or personal connection to the place. That was the case here.

Local knowledge is especially important when it comes to agriculture. Ragab Hafiez, a hydrogeologist and geologist working for DASCO, studies Egypt’s Western Desert. He gave us permission to re-publish some of his photographs showing the ground-based view of East Owinat, one of Egypt’s land reclamation projects aimed at making some desert areas suitable for agriculture. He also took the time to answer some questions about the satellite image that inspired the puzzler.

Q: What features visible in these images strike you as interesting?

A: The features visible in these images are the irrigated crops mainly clustered in a center-pivot irrigation systems; the diameter of the pivots range from 700 to 820 meters. The total irrigated area at the beginning of this year was about 79,000 hectares.

Q: Is there anything not visible that is worth noting?

A: East Owinat is an interesting area located at the far south of Egypt. It’s an arid to hyper-arid area, the rainfall is nil, and fossil groundwater is the only source of water in the area.

The area is covered with a thin sheet of loose sand, followed by the thick sandstone rock bed. The sandstone beds belong to the Nubian sandstone formation deposited through the Lower Cretaceous and Jurassic periods.

The water wells in the area are usually drilled to depths of 200 to 350 meters (650 to 1150 feet) below the ground surface. The water level ranged from 30 to 60 meters (100 to 200 feet) below ground.

Q: Do you happen to know what crops are planted here, and the reason for the various green/brown patters?

A: The crops cultivated in the winter season are wheat, barley, potatoes, and alfalfa. Virgin soil, fresh water (salinity less than 700 parts per million), mild weather, and long daily sunlight hours are all factors that combine to produce high-quality and prolific crops.

The green areas are currently cultivated, while the brown areas are left without cultivation this season.

Wheat fields. Photo by Ragab Hafiez.


Potato fields in the desert. Photo by Ragab Hafiez.


In Coastal Peru, Fog Begets Life

January 31st, 2017 by Kathryn Hansen


It might seem unlikely that vegetation can survive in a sandy coastal environment that receives little rain, but plant communities along Peru’s southern coast have found a way.

In December 2016, we published the top image showing a unique perspective of fog. From space, you can see the vast expanse of marine stratocumulus sweeping inland to fill some of Peru’s deep valleys. It is the visible outcome of unseen atmospheric circulation and ocean currents.

From the ground, visibility would be limited (assuming the cloud layer is reaching all the way down to the ground). Depending on your location, experiencing fog might not be too unusual. In coastal Chile and Peru, it’s most common to get fog like this during the austral winter (June through August) and early spring. Plant communities called “lomas” depend on it for their survival.  Instead of relying on rainfall, the plants get much of their water by combing droplets out of the air as dense fog passes by.

Ralf Hesse, a scientist at the State Office for Cultural Heritage in Germany, has used remote sensing to study Peru’s lomas. He provided the second image above, which shows the view from a study site located about 80 kilometers (50 miles) northwest from the top-left corner of the satellite image. The loma pictured is composed of the species Tillandsia. But depending on the location, lomas can contain anything from grasses and shrubs to small trees.