([syndicated profile] epod_feed Aug. 20th, 2017 03:01 am)


Each Sunday we present a notable item from our archives. This EPOD was originally published August 22, 2002.

Provided by: USGS - Water Resources of Alaska

Summary authors & editors: Martin Ruzek; USGS

These photographs show an eastward-looking view of a small section of the Hubbard Glacier in southeastern Alaska. Hubbard Glacier is the largest tidewater glacier on the North American continent. It has been thickening and advancing toward the Gulf of Alaska since it was first mapped 1895 in stark contrast with most glaciers, which have thinned and retreated during the last century. The advancing terminus of the glacier created a "squeeze-push" moraine in front of Gilbert Point that blocked the tidal exchange between Disenchantment Bay (bottom of photos) and Russell Fiord (top of photos), creating Russell Lake earlier this summer. The lake rose to 18.6 meters (61 feet) above sea level over 2 1/2 months before the rock and ice dam broke, creating the second largest glacial lake outburst worldwide in historical times. On August 14 the trapped water in the 70-square-mile (18,000 ha) lake broke free to the ocean in a spectacular roiling and chaotic 36 hours, making the torrential channel into the sea an extremely fast-moving and dangerous river full of large chunks of ice and debris.

Photographs made by the U.S. Geological Survey, the U.S. Forest Service, Yakutat Range District and National Park Service, Yakutat Ranger Station.

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([syndicated profile] epod_feed Aug. 19th, 2017 03:05 am)

Miraged boats

Today and every Saturday Earth Science Picture of the Day invites you to rediscover favorites from the past. Saturday posts feature an EPOD that was chosen by viewers like you in our monthly Viewers' Choice polls. Join us as we look back at these intriguing and captivating images.

Flying DutchmenPhotographer: Mila Zinkova

Summary Author: Mila Zinkova

January 2012 Earth Science Picture of the Day Viewer's Choice Like many people who live next to an ocean I’ve long been spellbound by the legend of the “Flying Dutchman”. For some time now, I’ve been on the lookout for such a vessel and on a warm, calm day this past November, I got lucky. My eyes were drawn to a ship on the horizon and what a ship it was... it looked as it was cut in slices and floating inside a wave! As I watched, it kept changing appearance. I was sure it was sailed by ghosts – this was indeed the Flying Dutchman. I looked around a little more, saw another such ship and then spotted a small sailboat that had an inverted boat atop it and even more strangely, another one hanging above it in the air (lower photo). To see a Flying Dutchman was eerie but to see several all at once was really quite bizarre. 

There had to be another explanation to these odd apparitions. When I got home, I sent animations of my Flying Dutchmen to Dr. Andrew Young of San Diego State University, asking him how a ship that’s cut in slices could be floating inside a wave. Dr. Young described the scenes thus:

"I think what happens here in the first animation is that the superior mirage includes some of the foreground sea surface, as well as the ship itself. As the mirage changes, there are multiple images of alternately erect and inverted portions of this region that includes the sea horizon. The animation nicely reveals this. So sometimes the 'fold line' of the image includes the ship, and you see a vertically stretched image of the part of the ship near the waterline, sandwiched between two images of the foreground sea surface."

"The second animation, showing interesting short-term changes, also shows a few frames with multiple images of the ship. You can see now and then a bit of sky miraged beneath the ship, where the stacks of cargo on its deck are lowest. I have the impression that waves on the inversion were causing slight oscillations in the structure of this mirage."

So it seems my Flying Dutchmen were mirages of ships sailing along the miraged sea surface with the miraged sky adding to the picture. To someone hoping to see an actual ghost ship this explanation might be just a little bit disappointing. Still, when you visit the seashore, keep your eyes peeled to the horizon – it seems to be a mysterious place.

([syndicated profile] epod_feed Aug. 18th, 2017 03:01 am)

Double Waterspouts - Double Lightning (1)

Photographer: Antonios Lyras 

Summary Authors: Antonios Lyras; Jim Foster

The photo above showing two waterspouts and two cloud-to-ground lightning strikes was captured near Mykonos, Cyclades, Greece, on the morning of May 5, 2017. When lightning and or a wall cloud are observed in proximity to a waterspout, as shown here, the spout is tornadic rather than a fair-weather whirlwind. So it's time to seek shelter. While fair-weather waterspouts arise in relatively stable air masses, tornadic spouts, in the Mediterranean Sea region, tend to form in frontal zones -- during the passage of a strong cold front.

Photo Details: Camera Model: NIKON D5200; Lens: 18.0-55.0 mm f/3.5-5.6; Focal Length: 46mm (35mm equivalent: 69mm); Aperture: ƒ/8.0; Exposure Time: 6.000 s; ISO equiv: 100; Software: Adobe Photoshop Lightroom 5.4 (Windows). 

([syndicated profile] epod_feed Aug. 17th, 2017 03:01 am)

Stone Door_30867385245_e302a4b64f_o (1)

Photographer: Chuck Sutherland

Summary Author: Chuck Sutherland

We're all on a long trip to the ocean. So are rocks. It may not seem exactly right, but rocks flow downhill under the same forces as water. The difference being that gravity must overcome the hardness of the rock, a gradient must be available for the rock to move down and their structure is sometimes able to prevent downward motion. Water shares some of these encumbrances but to much lesser degrees.

Shown above is the Stone Door, an artifact of flow found on the Cumberland Plateau in eastern Tennessee. More accurately, it's referred to as a joint, a place where pressure inside the rock is relieved by breaking. In this case, part of a cliff was sliding downslope, and the Stone Door was its relief point. Joints on the Cumberland Plateau often form in cliffs parallel to the cliff face. The Stone Door, while a fascinating feature, is not alone. There are dozens if not hundreds of similar features along the rim of the Plateau. Photo taken on October 2, 2016. 

Photo Details: Camera Model: Canon EOS M; Lens: EF-S10-18mm f/4.5-5.6 IS STM; Focal Length: 10mm; Focus Distance: 1.08m; Aperture: ƒ/4.5; Exposure Time: 0.077 s (1/13); ISO equiv: 100; Software: Adobe Photoshop CS5 Windows. 


Photographer: Juan Manuel Pérez Rayego

Summary Authors: Juan Manuel Pérez Rayego; Jim Foster

Following an afternoon thundershower in Merida, Spain, I happened to observe this handsome rainbow and striking supernumerary bows. In order for these supernumerary bows to be so obvious the minute rain droplets responsible for forming them, and their pastel colors, are likely very uniform in size. Larger raindrops produce the colors in the primary bow. Note that a portion of the faint secondary rainbow is visible at top left. Photo taken on June 25, 2017.

Photo Details: Dslr + 24-105mm; 105mm; polarizer filter; Adobe Photoshop. 

([syndicated profile] epod_feed Aug. 15th, 2017 03:01 am)

Circular_Rainbow_GS_20170624_Rainbow_1112_Pan_v2 (3)

Photographer: Göran Strand

Summary Author: Göran Strand

Rainbows are always opposite the Sun, centered below the horizon at the antisolar point. The lower the Sun's position in the sky, the higher the rainbow arches. I took the above photo from Vansbro, Sweden, at sunset. Together with its reflection on the water in the foreground, it forms a complete circle. However, had the Sun been any higher in the sky, the shape (of the primary bow and its reflection) would have been somewhat out of round or slightly elliptical. Photo taken on June 24, 2017.

Photo Details: A 6-shot mosaic made with a Nikon D800E camera; Nikon AF-S, 14-24mm, f/2.8 lens. 

Blkcyn203c_21may17 (2)

Blkcyn166c_21may17 (2)

Photographer: Ray Boren

Summary Author: Ray Boren

As if slices had been cut into a marbled cake of titanic size, curiously striped dark cliffs near Montrose, Colorado, rise precipitously above a roaring river, far below — a testament to geologic events well over billion years ago (and since) at what is today treasured as Black Canyon of the Gunnison National Park.

The grandeur is evident along scenic drives on Black Canyon’s rims, as illustrated in the photo above, taken at the South Rim’s Painted Wall overlook on May 21, 2017. At 2,250 ft (686 m) in height, the wall is considered to be the tallest cliff in Colorado. The Gunnison River, visible on the left, was named for 19th-century military officer and topographical surveyor Capt. John W. Gunnison. A second photo, taken at the Cross Fissures pullout, also shows snowy summits of the Sawatch Mountain Range, the source of the Gunnison.

For millions of years the river has been eroding a remarkably deep and narrow gorge through Precambrian rocks of the Gunnison Uplift. The uplift dome is composed mostly of dark metamorphic gneisses and schist, banded with pinkish pegmatite dikes, flecked with crystalline minerals like quartz, mica and feldspar, and even garnet. The sheer cliffs’ pegmatite veins were originally molten rock, or magma, which squeezed, or intruded, into fissures within the already-hardened gneisses and schist deep within the Earth. In some places the pegmatite, a granite more resistant to erosion than the surrounding rock, shows up in vertical fins; in others it manifests as serpentine bands that pattern the darker rock, as on the Painted Wall.

Like a long white-water waterfall, the Gunnison drops farther in 48 mi (77 km), as it cuts a trench through its sun-deprived and therefore black canyon, than the mighty Mississippi does in its 1,500 mi (2,414 km) journey from Minnesota to the Gulf of Mexico, the Park Service notes. Rim to river, the canyon walls range in height from 1,750 ft to 2,772 ft (533 to 845 m). Black Canyon was set aside as a national monument in 1933. In 1999 Congress passed, and President Bill Clinton signed legislation that expanded the boundaries and created Black Canyon of the Gunnison National Park.

Photo Details - Top: Camera Model: NIKON D3200; Lens: Tokina AT-X 124 AF PRO DX II (AF 12-24mm f/4); Focal Length: 12mm (35mm equivalent: 18mm); Aperture: ƒ/11.0; Exposure Time: 0.017 s (1/60); ISO equiv: 100. Bottom - same except: Lens: AF-S VR Zoom-Nikkor 70-300mm f/4.5-5.6G IF-ED; Focal Length: 70mm (35mm equivalent: 105mm); Exposure Time: 0.0020 s (1/500); ISO equiv: 400. 

([syndicated profile] epod_feed Aug. 13th, 2017 03:01 am)


Each Sunday we present a notable item from our archives. This EPOD was originally published August 12, 2002.

Provided by: USGS Hawaiian Volcano Observatory

Summary authors & editors: Martin Ruzek

Hollywood cannot compete with the real thing - lava pouring to the sea, an image that conjures scenes from Dante's "Inferno". Kilauea, the most active volcano on Hawaii, has been erupting constantly since 1983, drizzling over 2 cubic kilometers of lava across its flanks in a continual island building process covering over 100 square kilometers and adding over 200 hectares to Kilauea's southern shore. The current flow started on Mother's Day, May 12, when a new vent opened near the southwest base of Pu`u `O`o and has been inching steadily toward the coast. In the third week of July, the flow finally reached the sea, and began pouring into the ocean at a point known as West Highcastle and later at Wilipe`a. This view to the west shows photographers on the other side of the flow watching in awe as the 1000+ degree C magma pours into the ocean, forming new land as a bench of rock.

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EPOD_EncoreKanabstone690_7nov11 (2)

Kanabstone673_7nov11 (2)

Today, and every Saturday Earth Science Picture of the Day invites you to rediscover favorites from the past. Saturday posts feature an EPOD that was chosen by viewers like you in our monthly Viewers' Choice polls. Join us as we look back at these intriguing and captivating images.


Photographer: Ray Boren

Summary Author: Ray Boren

December 2012 Viewer's Choice About 50 years ago, W. Rex Brown was amazed by evocative patterns and pictures he noticed in sandstone near his hometown of Kanab, Utah. As many have observed since, the designs seem to mimic the landscape all around Kanab, which is the famed red-rock country of the Colorado Plateau along the Utah-Arizona border. The region is home to such national parks and monuments as Grand Canyon, Zion, Bryce Canyon and Grand Staircase-Escalante – all within striking distance of Kanab. When cut into slabs large and small, the images on the quarried stone evoke Colorado Plateau landscapes that appear to be decorated with ridges, buttes, pinnacles, valleys and eroded swirls (top photo).

Brown and a partner subsequently formed Western Hills Rock & Gem Inc. to market “nature’s most beautiful paintings” as Kanab Wonderstone, Kanab Goldenstone and Arizona Sierra, quarried in both Utah and Arizona. The photo at bottom shows the natural design of a cut boulder outside of the shop. Large pieces of sandstone are mounted on walls in the Kanab shop. Some are framed. Smaller stones have been transformed into clocks, paperweights, picture frames and figurines, such as howling coyotes. Occasionally slabs are painted by artists, who may insert barns, roads and fence lines, adding a pastoral effect to Nature’s gritty canvas. For most of the artful stones, what you see is what you get, but in a few cases, as with Arizona Sierra, the rock is treated with heat to bring out richer, terra-cotta tints.

According to postings in the Western Hills Shop, picture sandstone is actually part of the Shinarump Formation, laid down 180 million to 220 million years ago by water and wind. The U.S. Geological Survey describes the Shinarump as a basal conglomerate and pebbly sandstone member of the more extensive Chinle Formation, formed during the Late Triassic. The colors and designs within the rock are created by iron oxides, which filtered into the porous rock from mineral springs. Photo taken on November 7, 2012.

Photo Details: TOP - Camera Maker: NIKON CORPORATION; Camera Model: NIKON D60; Focal Length: 35.0mm; Aperture: f/5.3; Exposure Time: 0.033 s (1/30); ISO equiv: 400; Software: QuickTime 7.6.4. Bottom - Same except Focal Length: 20.0mm; Aperture: f/9.0; Exposure Time: 0.013 s (1/80); ISO equiv: 200.

([syndicated profile] epod_feed Aug. 11th, 2017 03:01 am)

On the road to MStH epod (8)

Photographer: Rebecca Roush

Summary Author: Rebecca Roush

The photo above was taken along the road to Mount St. Helens (Washington State) and shows evidence of volcanic activity well before the well-documented 1980 eruption. This lava flow (slab at top) covers an underlying assortment of pyroclastic rocks in varying stratifications. Mount St. Helens, a composite volcano, erupted for the first time 40-50,000 years ago. Composite volcanoes have steep sides and are made up of layers of lava, ash and other types of volcanic materials. When they erupt, they do so much more explosively than gently sloping volcanoes, such as Mauna Loa in Hawaii. Photo taken on June 19, 2017. 

([syndicated profile] epod_feed Aug. 10th, 2017 03:01 am)


Photographer: Stu Witmer

Summary Author: Stu Witmer

It's been more than 37 years since Mount St. Helens blew its top. That explosion created a huge blast zone that devastated all the plant and animal life in the area. Today, while the ground cover is obviously different from previously, the land at Loowit Viewpoint (c. 4,000 ft or 1,220 m) near the crater is blanketed with familiar wildflowers. Photo taken June 21, 2017.

Photo Details: Camera Model: Canon PowerShot SX280 HS; Focal Length: 10.88mm; Aperture: ƒ/4.5; Exposure Time: 0.0016 s (1/640); ISO equiv: 80. 

([syndicated profile] epod_feed Aug. 9th, 2017 03:01 am)

Whole_of_Lyra_HALF (2)

Photographer: Greg Parker 

Summary Authors: Greg Parker, Jim Foster

Featured above is a 4-frame mosaic showing the constellation of Lyra the Lyre. Lyra is nearly overhead at midnight during midsummer in the Northern Hemisphere. The brilliant bright, blue-white star at upper right is Vega (the Harp Star), the fifth brightest star in the night sky, having a magnitude of 0.03. It's relatively close by, just 25 light years away. The lyre itself is represented by 4 second and third magnitude stars in the shape of a parallelogram. Sulafat at lower left and Sheliak at lower right form the bottom of the lyre. In between them, just a little more than halfway towards Sheliak, is the well known Ring Nebula or M57. It's somewhat difficult to discern here but appears brighter and larger than any star in the vicinity. Also, note that the double star close to Vega, in the 10 o'clock position, is, in fact, Epsilon Lyrae - the famous double-double (each of the double stars is also a double).

Photo Details: Canon camera; 200mm lens; at f 3.8; the Trius M26C 10-Megapixel OSC CCDs; 2 hour exposure time using 10-minute sub-exposures. 

([syndicated profile] epod_feed Aug. 8th, 2017 03:01 am)

Orange Peel Fungus 2 (3)

Photographer: Cindy Todd 

Summary Author: Cindy Todd

Shown above is the orange peel fungus as observed on a little backpacking trip I took on the High Sierra Trail, near Bearpaw Meadow, in Sequoia National Park, California. The orange peel fungus, (Aleuria aurantia) is a cup type fungus, growing up to 4 in (10 cm) tall. It's easy to see how it gets its name. What I especially love about hiking and backpacking is the exploration -- finding things I've never seen before. Photo taken on June 8, 2017.

Photo Details: Camera Model: Canon PowerShot SX160 IS; Focal Length: 46.834mm; Aperture: ƒ/5.0; Exposure Time: 0.050 s (1/20); ISO equiv: 640. 

Olympic Lenticular Cloud  (1)

Photographer: Joe LaCour 

Summary Authors: Joe LaCour; Jim Foster

Shown above are silhouetted lenticular clouds as observed just north of the Olympic Range in northwestern Washington. These orographic, lee wave clouds persisted, appearing nearly motionless for several hours. Earthshine can be seen on the waxing crescent Moon. Near the horizon, below and to the right of the Moon, the planet Venus can be seen. Photo taken on November 3, 2016.

Photo Details: Camera Model: Canon EOS REBEL T2i; Focal Length: 25mm; Aperture: ƒ/4.0; Exposure Time: 0.050 s (1/20).