EPOD_EncoreRainbow_2011_07_21_Raab (3)

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: Herbert Raab 

Summary Author: Herbert Raab; Jim Foster

September 2011 Earth Science Picture of the Day Viewer's ChoiceThe photo above shows a jaunty rainbow stretching over a cornfield near Piberbach, Austria. My shadow clearly shows the direction of the antisolar point -- the only direction where rainbows can be observed. Note that the fainter secondary bow is also visible (at left). This bow is caused by two internal reflection of sunlight in raindrops. Since some light is lost with each additional reflection, secondary bows are only 43 percent as bright as the primary bow. Photo taken on July 21, 2011.

Photo Details: Canon EOS 550D camera; ISO 200; Peleng 8mm fisheye lens; f/8; aperture mode, corrected by -1 stop, resulting in 1/60 sec. exposure.

([syndicated profile] epod_feed Mar. 24th, 2017 03:01 am)

Osorno_IMG_4348 (2)

Photographer: Gabriela Carvalho

Summary Author: Gabriela Carvalho

Shown above is a beautiful springtime view of Osorno Volcano as seen from Lake Todos los Santos in the Los Lagos Region of Chile. Though quiescent for over a century, Osorno erupted at least 11 times between 1575 and 1869.The symmetrical shape and snowcapped summit (8,701 ft or 2,652 m) of this stratovolcano is renown in Chile as a geographic symbol. It's also known for its resemblance to Mount Fuji, Japan.

As a result of its maritime (marine west coast) climate, Osorno's flanks receive abundant snowfall during the colder months. Glaciers cover its upper slopes -- above approximately 5,900 ft (1,800 m). Photo taken on November 21, 2016.

Photo Details: Camera Maker: Apple; Camera Model: iPhone 7; Focal Length: 3.99mm (35mm equivalent: 72mm); Digital Zoom: 2.287x; Aperture: ƒ/1.8; Exposure Time: 0.0002 s (1/4808);

ISO equiv: 20.

([syndicated profile] epod_feed Mar. 23rd, 2017 03:01 am)

Oystercatcher_AMOY Rainsford 1 (2)

Photographer: Rob Sheridan

Summary Author: Rob Sheridan

The American Oystercatcher (Haematopus palliatus) is a striking coastal seabird noted for its bright, functional beak, designed to extract mollusks from intertidal sediments. New England populations are migratory, wintering along the American Gulf Coast and breeding along New England’s rocky shoreline. Before the mid-1800’s Oystercatchers were a very common spring and summer sight along the northeastern coast of the United States and Canada, but hunting, wild egg and feather collecting, and habitat encroachment lead to its near extinction.

Although they received government protection under the 1918 Migratory Bird Treaty Act, Oystercatcher numbers continued to decline. In the early 2000s, after the total North American population fell to fewer than 10,000 individuals, efforts to protect the species and its dwindling habitat intensified. These combined public and private habitat protection efforts have been remarkably successful, with a clear rebound in the New England population in recent years. In this image, an American Oystercatcher on Rainsford Island in Boston Harbor Islands National Recreation Area protects its nesting area with its distinctive shrill cry. Previously, its shrill cry was not enough to ensure survival, but the addition of legislated habitat protection seems to be working! Photo taken on June 6, 2015.

Photo Details: Camera Maker: NIKON; Camera Model: COOLPIX S9700; Focal Length: 162mm (35mm equivalent: 750mm); Digital Zoom: 1.200x; Aperture: ƒ/6.4; Exposure Time: 0.0080 s (1/125); ISO equiv: 180.

([syndicated profile] epod_feed Mar. 22nd, 2017 03:01 am)

Trails Of Lights And Fires On Mount Etna - Unesco World Heritage Site DG (5)

Photographer: Dario Giannobile

Summary Author: Dario Giannobile

Mount Etna, on the island of Sicily, Italy, is erupting once again. This is the second time this month that Etna (10,922 ft or 3,329 m) has unleashed noteworthy Strombolian explosions. The second eruptive event began on the morning of March 15, 2017. The lava fountain featured above is erupting from Etna's southeast crater. When this shot was snapped, during the night of March 16, 2017, lava was flowing to the base of the volcanic cone and beginning to ooze down the south flank of the mountain.

This fiery landscape was lit from above by a waning gibbous Moon and a starry sky. The long exposure used here results in the star trails rotating about the North Star. In the foreground note that a thick snowpack lower down the mountain partially covers the volcanic landscape.

Photo Details: Camera Model: Canon EOS 7D; Lens: EF70-200mm f/2.8L IS II USM; Focal Length: 200mm; Aperture: ƒ/4.0; Exposure Time: 25.000 s; ISO equiv: 400; Software: Adobe Photoshop CC 2015.5 (Windows).

Queensland_crep_rays_IMG_4214 (2)

Photographer: Terence West

Summary Authors: Terence West; Jim Foster

I captured this beautiful display of crepuscular rays near Warwick, Queensland, Australia, at sunset on January 15, 2017. Sunlight streaming through gaps in building cumulus clouds near the western horizon form the bright rays while the dark lanes result from cloud turrets that effectively blocked the Sun. Look for rays such as this when clouds, most often cumulus clouds, are observed on the horizon where the Sun is setting. Also, look toward the opposite horizon to see if anticrepuscular rays can be detected.

Photo Details: Camera Model: Canon EOS 70D; Lens: 5mm; Focal Length: 5.0mm; Aperture: ƒ/3.5; Exposure Time: 0.0006 s (1/1600); ISO equiv: 100; Software: PaintShop Pro 15.00.

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

Murrieta_halo_7P7A0221-Edit (3)

Photographer: Mark Ritter

Summary Authors: Mark Ritter; Jim Foster

Featured above is an attention-getting 22 degree solar halo, an upper tangent arc (tangent to the top of the halo) and sundogs (on the sides of the halo and at the same elevation as the Sun). It was observed over Murrieta, California, on February 2, 2017. Sunlight passing through hexagonal plate ice crystals in cirrus clouds form the 22 degree halo and the arcs seen here. Because the crystals are oriented horizontally (think of a leaf as it falls to the ground) when they're positioned at the same elevation as the Sun and approximately 22 degrees from the solar disk their particular alignment allows this segment of the halo to be considerably brighter than the remainder of the halo. In addition, since the oriented crystals that form the sundog tend to be larger than the randomly oriented crystals that generate the 22 degree halo, they're generally much more colorful. Sundogs can be seen best when the Sun is low in the sky -- they cannot be viewed when the Sun attains an elevation of 61 degrees. Note also the contrail and its distinct shadow.

Photo Details: Camera Model: Canon EOS 5D Mark III; Lens: EF24-105mm f/4L IS USM; Focal Length: 24mm; Aperture: ƒ/16.0; Exposure Time: 0.0020 s (1/500); ISO equiv: 100; Software: Adobe Photoshop Lightroom 6.8 (Macintosh).

([syndicated profile] epod_feed Mar. 19th, 2017 03:01 am)


Each Sunday we present a notable item from our archives. This EPOD was originally published March 31, 2003.

Provided by: Drew Patrick, Fox Lane High School

Summary authors & editors: Drew Patrick; Martin Ruzek

This pyroclastic flow deposit is located in Poseidon's Gardens, near Citara on the island of Ischia, Italy. Ischia, just off the coast from Naples and notorious Mt. Vesuvius, is dominated by Mt. Epomeo. This deposit indicates the violent nature of pyroclastic flows and the turbulence and deformation possible within these volcanic features. These soft volcanic layers were deposited about 10,000 years ago and deformed as the flow slid down the side of the mountain, or possibly as the soft sediments were covered by a more viscous lava flow during the same eruption. Poseidon's Gardens is a day spa that takes advantage of a fairly shallow magma chamber that still heats the groundwater to over 90 degrees C. This water is pumped and piped throughout the spa, providing a series of pools of varying temperatures.

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

EPOD_EncoreLenticular Clouds A5 - 20110626 - 02 

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: Graham Stephen 

Summary Author: Graham Stephen; Jim Foster

July 2011 Earth Science Picture of the Day Viewer's ChoiceThese stacked lenticular clouds were observed from the A5 Road just east of Tryfan, Wales, in the mountain pass between the Carneddau and Glyderau ranges. Normally found in the lee of mountains, altocumulus lenticularis are a type of stationary wave cloud that results when air is forced to rise over elevated terrain. Water vapor within the wave layer condenses at the wave crest if the temperature is sufficiently cool (dew point temperature), forming a smooth, lens-shaped cloud. The cloud evaporates due to adiabatic heating when it sinks into the drier wave trough. In this way, clouds appear at intervals closely related to the wavelength. Photo taken on June 26, 2011.

Photo Details: Camera Maker: Canon; Camera Model: Canon EOS 500D; Focal Length: 30.0mm; Aperture: f/8.0; Exposure Time: 0.0020 s (1/500); ISO equiv: 100.

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

Venus (4)

Photographer: Meire Ruiz

Summary AuthorsMeire Ruiz; Jim Foster

Shown above is a montage of the path of Venus during a brief time lapse (2 minutes), as observed on February 13, 2017, from Santos, Brazil. Approximately 30 percent of our sister planet, some 41,776,649 miles distant (67,233,000 km), was illuminated at the time. The change in brightness you see is due to the presence of thin clouds over Santos. Unlike the visible planets that lie further away from the Sun (Mars, Jupiter and Saturn), Mercury and Venus, when they're in the crescent phase, appear brightest to Earthlings. When these two planets are closest to us, directly in-between the Earth and the Sun (new phase), they can't be detected because the Sun is too bright. But when they're in the full phase, they're on the other side of the Sun from us and so, much further away with a much smaller apparent diameter.

Venus thus appears brighter as it gets thinner. It'll be very bright tonight (magnitude -4.7) when it's low in the western sky and only about 3 percent of its surface is lit. Use binoculars to see its crescent shape -- Mercury can be seen below and slightly to the left of Venus.

Photo Details: Canon SX40 HS camera; 1/100 sec. exposure; ISO 10; f/5.8; Zoom 140x.

Click for video

Photographer: Mila Zinkova
Summary Author: Mila Zinkova

Shown above is a tidal pool on the California coast, near San Francisco, featuring a hermit crab (Pagarus sp) and a sea worm (Polychaete). Click on the photo to see the interaction between this crab (in the black shell) and two others and the hapless sea worm. I started filming the worm without realizing I was filming the last few seconds of its tenuous life. Hermit crabs are common in tidal pools. They live in shells that were freed by snails. These shells serve as their home and protect them from would-be predators. They're on constant lookout for a new shell and are often seen fighting with other hermit crabs over what they perceive is a good one. Hermit crabs go to a great extend to retrieve a better shell. Although mostly scavengers, they also attack grass shrimps and tube worms when the opportunity presents itself. As I was filming the sea worm, it touched one of the crab's antennas, most likely by accident, but this is how the action began.

According to Dr. Thomas Carefoot, Emeritus in the Department of Zoology, at the University of British Columbia, during the 8.5 seconds of this video, the initial withdrawal of the worm at the 2.5 second mark is mediated by the chemotactic stimulation of sensory appendages (antennae, palps, cirri) on the worm's head. The question arises as to whether the worm's response was innate or was a result of some type of chemical emanation from the crab's antenna. This leads to a corollary question, whether the worm has remembered a similar previous contact and has responded accordingly. For invertebrates such as mollusks and sea stars, such a memory capability is actually quite well known, but whether it exists in a Polychaete worm hasn't yet been determined. Dr. Carefoot took screenshots from the video and made a video montage with detail descriptions of just what is occurring. Click here to see it.

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


Brycearch422c_9feb17 (3)

Photographer: Ray Boren

Summary Author: Ray Boren

Bryce Canyon National Park’s spectacular rim-rock amphitheaters, and their weathered cliffs, hoodoos, niches and arches, are products of many natural forces and phenomena. Paramount among the sculptors at work in this fairyland on the edge of a high plateau (Bryce isn't really a canyon) are water — including snow and ice — and widely variable temperatures. This is called the freeze-and-thaw cycle, which results in frost wedging, and thus erosion.

This is beautifully obvious in winter, when the park’s red- and coral-themed architecture is blanketed and streaked by fresh snow, with a sprinkling of deep-green juniper trees, pinyon and ponderosa pines speckling the rims and distant vistas, as shown above in the top photo taken at Sunset Point (elevation: 8,000 ft/2438 m). The view is to the southeast. In the blue distance — about 80 mi (129 km) away — is the domed 10,348 ft (3154 m) summit of Navajo Mountain, a laccolithic peak with an igneous core that rose and pierced the sedimentary Colorado Plateau of what is today the Southwestern United States.

According to the National Park Service, frost wedging works like this: During fluctuating temperatures about 180 days a year, warming meltwater from snow and ice seeps into Bryce’s stacked and fractured rock. The stone is primarily Claron Formation limestone. Also known as the Pink Cliffs, these layers formed 35 million to 55 million years ago as a result of sedimentation in ancient lakes. When temperatures plunge, the water refreezes, expands, gradually fractures and erodes the rock. The national park’s signature hoodoos, or vertical columns, and its broken walls and even windows develop in the stone, as shown in a second photo, featuring Bryce’s lovely but misnamed Natural Bridge. It's technically an arch, not a bridge, which by definition has, or once had, a flowing stream beneath, helping to form it. Both photos were snapped on February 9, 2017.

Photo Details: Top - Camera Model: NIKON D3200; Lens: AF-S VR Zoom-Nikkor 70-300mm f/4.5-5.6G IF-ED; Focal Length: 70mm (35mm equivalent: 105mm); Aperture: ƒ/11.0; Exposure Time: 0.0020 s (1/500); ISO equiv: 360. Bottom - same except: Lens: Tokina AT-X 124 AF PRO DX II (AF 12-24mm f/4); Focal Length: 22mm (35mm equivalent: 33mm); ISO equiv: 400.

([syndicated profile] epod_feed Mar. 14th, 2017 03:01 am)

Slugpaths_P1100996 2 (1)

Slug2_P1110005 (6)

Photographer: Patti Weeks

Summary Author: Patti Weeks

Generally considered a garden and farmland pest, the garden slug can also produce abstract art, as a result of grazing on the algae of flat surfaces. These intriguing patterns, as photographed on the siding of a house, are the handiwork of the Limax Maximus, one of many species of gastropods (translates as stomach-foot). Native to Europe and the Mediterranean countries of Africa, this herbivorous, great grey slug, also referred to as the leopard slug due to the spots on its body, is present in 46 of the 50 U.S. states. It's common in warm, humid environments, and can grow up to 4 in (10 cm) long.

These zigzag tracks are evidence of one of the slug’s eating behaviors made by its radula (comparable to a tongue) that contains chitinous ribbons or rows of hundreds of teeth (also known as denticles.) The radular teeth, continually being worn down and replaced, are used as a rake to scrap diatoms and algae with the slug’s downward facing mouth before the food is eased into the esophagus with the help of sticky mucous. The slug’s actual feeding activity is rarely observed first-hand, as slugs are typically more industrious at night, in rainy weather or in damp greenhouses or crawl spaces.

The width of the zigzags range from about 1/4 in (0.6 cm) to 1/2 in (1.3 cm).The bottom photo shows a size comparison of the patterns with the photographer’s thumb. Photos taken March 16, 2016.

Photo Details: Top - Camera Maker: Panasonic; Camera Model: DMC-ZS7; Focal Length: 4.1mm (35mm equivalent: 25mm); Aperture: ƒ/3.3; Exposure Time: 0.010 s (1/100); ISO equiv: 80. Bottom - same except: Aperture: ƒ/4.0; Exposure Time: 0.0025 s (1/400).

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

MyrtosBeach360 (2)

Photographer: Nick Sparacello

Summary Author: Nick Sparacello

Shown above on this 360 degree panorama is Myrtos Beach near Cephalonia, in western Greece. Littoral drift (also called longshore drift) has helped shaped the beach front. The striking blue color of the water is due primarily to the action of wind waves and sediment. As high energy waves curve along the beach they pick up fine bits of marble material (metamorphosed limestone) that create sediment plumes, tinting the water a shade of turquoise. Photo taken on October 5, 2016.

Photo Details: Camera Model: NIKON D3300; Focal Length: 18mm (35mm equivalent: 27mm); Aperture: ƒ/8.0; Exposure Time: 0.0016 s (1/640); ISO equiv: 100; Comment: Kolor stitching | 32 pictures | Size: 15000 x 7500 | Lens: Standard | RMS: 2.71 | FOV: 360.00 x 180.00 ~ 0.00 | Projection: Spherical | Color: LDR |; Software: Adobe Photoshop CS6 (Macintosh).

([syndicated profile] epod_feed Mar. 12th, 2017 04:01 am)


Each Sunday we present a notable item from our archives. This EPOD was originally published March 11, 2003.

Provided by and copyright: Lisa Tauxe, Scripps Institution of Oceanography

Summary authors & editors: Jim Foster; Lisa Tauxe

The above picture was taken last April on the island of Cyprus and shows the Troodos ophiolite, which is a section of oceanic crust created about 92 million years ago in what was then the Tethys Ocean. In essence, the tip of the current Troodos mountain range formed 8,000 meters (26,000 ft) below sea level. This ophiolite was later thrust, through complex geological processes, more than 2,000 meters (6,500 ft) above sea level. Over the eons, erosion has lowered the elevations of the Troodos range - the highest point today is approximately 1,950 meters (6,340 ft) above sea level. The Troodos ophiolite consists of basic and ultrabasic pillow lavas, fringed by sheeted dikes. On the photo, to the left (foreground), is a prominent feeder dike of the ophiolite, and in the background, associated sheet flows are evident.

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