Earth Science Picture of the Day

Crystal Cave in Sequoia National Park

2012-02-09T03:01:00-05:00

Photographer: Nel Graham
Summary Author: Nel Graham

The photo above showing an interior area of Crystal Cave was taken in Sequoia National Park on the western flank of the Sierra Nevada Range in California. Crystal Cave is one of 240 known caves found within the park. It's a classic solution cave; created in carbonate and sulfate rocks when slow moving groundwater dissolves the rock, in this case marble, to form irregular passages and in some instances, cavernous openings. In the portion of the cave shown here, flowstones dominate from the ceiling to the floor. Though not as large as some of the more famous caves in the world, Crystal Cave is a welcome respite on hot summer days as its interior temperature stays at approximately 48 F (9 C) year round. It's open to the public from mid May to mid October. Photo taken in the summer of 2001.

Photo details: Camera Maker: OLYMPUS OPTICAL CO.,LTD; Camera Model: C3100Z,C3020Z; Focal Length: 6.6mm; Aperture: f/2.8; Exposure Time: 0.033 s (1/30); ISO equiv: 400; Exposure Bias: none; Metering Mode: Matrix; Exposure: program (Auto); Flash Fired: Yes (Auto, return light detected); Orientation: Normal; Color Space: sRGB.

Sea Stacks of Accreted Terranes Along the Southern Oregon Coast

2012-02-08T03:01:00-05:00

Photographer: Marli Bryant Miller; Marli's Web site
Summary Author: Marli Bryant Miller

The southern Oregon coast hosts thousands of sea stacks, freestanding rocks that rise above the ocean surface. They form because of erosion: as waves gradually wear away a headland, they don't remove everything at once. The erosional remnants are left as sea stacks. A fascinating corollary to this process is that sea stacks represent earlier positions of the coastline. Some lie nearly a mile away from today's shore!

These particular rocks consist of folded layers of chert, a sedimentary rock made of countless silica-producing microscopic floating organisms called radiolarians. In deep marine environments, radiolarians accumulate at the very slow rates of about 30 to 80 ft (10 to 25 m) in a million years. These rocks were added (accreted) to the North American land mass when they were scraped off the subducting seafloor at the continent's edge. They're part of the so-called Franciscan Assemblage, a series of crustal fragments that were accreted during the late Cretaceous Period. Photo taken on December 6, 2011.

Photo details: Camera Model: Canon EOS 5D Mark II; Lens: EF17-40mm f/4L USM; Focal Length: 28.0mm; Aperture: f/11.0; Exposure Time: 0.200 s (1/5); ISO equiv: 50; Orientation: Normal; Color Space: Adobe RGB (1998); Software: Adobe Photoshop CS4 Macintosh.

Shark Teeth

2012-02-07T03:01:00-05:00

Photographer: Mila Zinkova
Summary Author: Mila Zinkova; Jim Foster

The photo above shows a huge, ebony colored tooth of an ancient Cenozoic Era shark known as a megalodon. On top of it are two teeth from a modern era great white shark found on a California beach. Fossils indicate that megalodons reached a length of 52 ft (16 m); this compares to a length of 20 ft (6 m) for an exceptional great white shark. A shark's tooth is one of the most commonly found fossils since sharks go through several sets of teeth during their life. Their teeth are lost routinely but new ones constantly grow in to replace the ones that are surrendered.

The great white sharks at the left were photographed when I went on a cage-diving expedition off Guadalupe Island, Mexico. I was on deck and not in the cage while these shots were taken. The sharks were ravenously feeding on tuna.

Below, the remains of a whale washed ashore at Ocean Beach in San Francisco in September 2010 show bite marks left by great white sharks. Though the species of whale couldn't be identified, it was easy to tell that the bite marks were from a great white. A 2008 study determined that a great white shark specimen 20 ft (6 m) in length could exert a bite force of over 4,000 lbf (18,000 newto ns), more than enough to cut through bone but not as forceful as the bite of a tiger shark or that of a Nile crocodile.

Oh, the shark, babe, has such teeth, dear
And it shows them pearly white
Ya know when that shark bites, with his teeth, babe
Scarlet billows start to spread....

- Mack the Knife

Distorted Moonset Sequence

2012-02-06T03:01:00-05:00

Photographer: Randy Scholten
Summary Author: Randy Scholten; Jim Foster

This photo sequence showing an extraordinary moonset was taken from the shores of Garrison Lake in Port Orford, Oregon. The camera was facing west; looking across the lake, beyond the narrow foredune and out toward the Pacific Ocean. A very clear atmosphere enabled me to watch the Moon set all the way down to the horizon. The distortion that occurred as it descended was quite remarkable -- the Moon's shape was changing as fast as I could snap a picture.

Though we're enthralled with the rising full Moon, we rarely see it set. For one thing, a lot of people are still sound asleep in the early morning hours as the full Moon is working its way toward the horizon. Additionally, our attention is often diverted in the direction of the brightest part of the sky. As the full Moon sets, sunrise, on the opposite horizon, is more captivating than a pale orb that's dimming as quickly as the Sun is rising. However, on this early winter's morn, the Moon did the best it could to make us swivel our heads. The 16-shot moonset sequence begins at 7:10 a.m. (local time) on the morning of January 8, 2012. The Moon was one day shy of being full. I first noticed the Moon's flattened disk (top left) and watched as it changed to a light bulb, an acorn, a square patch of light and finally to a mere slice of itself (bottom right). The "man in the Moon" is hard to see but on the photos at upper right (second and third photos from the right), it appears he's putting on his pants.

Atmospheric refraction is responsible for the distorted shapes. Because the Moon's disk (and the Sun's too) is about half a degree in diameter, light from its bottom passes through slightly more air than at its top as it sets or rises -- the path length of moonlight is greater at the bottom of the disk. Thus, the bottom is refracted upwards more than the top, resulting in the bizarre distortions. Not only was the Moon distorted, but also multiple temperature inversions in effect created multiple Moons -- best seen on second photo from right on top row and in the middle photos of the bottom row. Note also the blue-green glint of light atop the Moon on the bottom row of photos (second photo from left). This is a mock mirage, green flash. What a show!

Photo details: Camera Maker: NIKON CORPORATION; Camera Model: NIKON D700; Lens: 50.0-500.0 mm Sigma APO/DG/HSM f/4.0-6.3; Focal Length: 500mm (35mm equivalent: 500mm); Focus Distance: Infinite;
Aperture: f/6.3; Exposure Time: 2.000 s; ISO equiv: 400; Exposure Bias: -1.67 EV; Metering Mode: Matrix; Exposure: program (Auto); White Balance: Auto; Flash Fired: No; Orientation: Normal; Color Space: sRGB.
All photos were taken within five minutes of each other and none were enhanced in any way -- they're straight out of the camera.

Fireball Over Corfu, Greece

2012-02-05T03:01:00-05:00

Photographer: Bill Metallinos; Bill's Web site
Summary Author: Bill Metallinos; Jim Foster

The photo above showing a startling fireball appearing to rip apart the night sky was seen during a star observation session at Mount Pantokrator on the Greek island of Corfu. I had set my camera up to get a picture of our small group and before long this brilliant meteor lit up the surrounding landscape. It was approximately -8 magnitude or about 25 times brighter than Venus at its brightest -- so bright that we were bathed in a sea of blue-green light. You can see the reflection on my 16 in (41 cm) telescope, on the table at right-center and on the side of my car. Click here to see a short animation.

Photo details: Canon EOS 40D camera; 15mm fisheye lens; f/2.8; ISO 800; 30 second exposure; Photoshop; Cropped.

Blue Ice Crystals

2012-02-04T03:01:00-05:00

Photographer: Trent LaCour
Summary Author: Trent LaCour; Joe LaCour; Jim Foster

These angular ice crystals formed on the side of a rock outcrop near Dungeness, on Washington's Olympic Peninsula. This picture was taken in the shaded portion of a gravel pit just after a cold snap -- morning temperatures were in the mid- to upper 20s F (about -3 C). The crystals are approximately three-quarters to one and a quarter inch (20-32 mm) wide. The blue hue of the crystals is attributed to light from the sky, which tints daytime shadows, especially if the sky is clear and the Sun is low -- as was the case this day. Additionally, water and ice are intrinsically bluish since they absorb more in the red portion of the spectrum than in the blue. However, for this inherent coloration to be readily noticeable, the ice would generally need to be much thicker than an inch or so. Photo taken on January 2, 2012.

Photo details: Camera Maker: Canon; Camera Model: Canon PowerShot A480; Focal Length: 6.6mm; Aperture: f/3.0; Exposure Time: 0.0080 s (1/125); ISO equiv: 80; Exposure Bias: none; Metering Mode: Matrix; White Balance: Auto; Flash Fired: No (enforced); Orientation: Normal; Color Space: sRGB; Software: Adobe Photoshop CS Macintosh. The blue color is as it was -- no processing was done to this photo. Camera was positioned about 3 in (8 cm) from the crystals -- field of view was approximately 1 in (2.5 cm).

Ice on Utah Lake

2012-02-03T03:01:00-05:00

Photographer: Patrick Wiggins; Patrick's Web site
Summary Author: Patrick Wiggins; Jim Foster

This photo shows randomly oriented elliptical openings in the ice of mostly frozen Utah Lake in northern Utah. It was taken through the open window of a small aircraft flying approximately 1,000 m above the surface on December 27, 2011. Note that despite the orientation of the openings, the biggest has a major axis of perhaps 20 m in length; pale triangles have formed on their lower ends, which are more or less facing the same direction. The apexes of the triangles are pointed toward the southeast -- north is at right. This gives a clue as to their origins; deposits of spray across the open water from northwest winds.

A number of factors likely come into play to determine the teardrop shape, size and orientation of these holes, including strength, persistence and direction of the wind and the thickness and compression and tension of the ice. Moreover, because Utah Lake is shallow, average depth is about 3 m, strong winds can stir up bottom sediments, which will ultimately affect surface conditions and freeze-up rates. As winter wears on, the holes eventually freeze over, and the lake ice becomes so thick that small aircraft looking for the nearby airport when visibility is poor have been known to mistakenly land on the completely frozen lake surface.

Photo details: Camera Maker: NIKON CORPORATION; Camera Model: NIKON D70; Lens: Sigma 28-300mm F3.5-6.3 DG Macro; Focal Length: 35mm (35mm equivalent: 52mm); Aperture: f/9.0; Exposure Time: 0.0031 s (1/320); ISO equiv: 400; Exposure Bias: none; Metering Mode: Matrix; White Balance: Auto; Flash Fired: No; Orientation: Normal; Color Space: sRGB; Software: Ver.1.03.

Where’s the Duck?

2012-02-02T03:01:00-05:00

Photographer: Ray Boren
Summary Author: Ray Boren

The photo above showing curious alabaster footprints on the partially frozen Bear River in northern Utah was captured on December 3, 2011. I suspect there was a skiff of snow on the ice when a shorebird or duck wandered across it, ever so slightly crunching and compressing the snow underfoot. As a result, perhaps these webfoot shapes were slower to melt and/or sublimate than the thin, undisturbed snow layer that otherwise disappeared before I snapped this picture. If it had been taken today, Groundhog Day in the United States and Canada, based upon Germanic traditions involving other creatures entirely, one might wonder if the vanished bird had not wandered off in search of its shadow, pondering how long this winter might last.

The Bear River follows a serpentine course out of the Uinta Mountains, through a corner of Wyoming and a patch of Idaho, then back into Utah toward the "dead sea" known to most people as the Great Salt Lake. The delta, on the northeast corner of the lake, is one of the most important fresh-water stops for migratory birds along the central flyway from Canada to Mexico. Millions of birds died during avian botulism outbreaks in the area in the early twentieth century motivating the U.S. Federal government to create the Bear River Migratory Bird Refuge here in 1928.

Photo details: Camera Maker: NIKON CORPORATION; Camera Model: NIKON D60; Focal Length: 240.0mm; Aperture: f/5.6; Exposure Time: 0.0020 s (1/500); ISO equiv: 100; Exposure Bias: none; Metering Mode: Matrix; Flash Fired: No; Orientation: Normal; Color Space: sRGB; Software: QuickTime 7.6.4.

Snow Shadows

2012-02-01T03:01:00-05:00

Photographer: Stu Witmer
Summary Author: Stu Witmer

What’s going on here? I’ve asked around and received some interesting possibilities, but so far no one I've talked to has ever seen this particular effect before. I took these photos on a recent trip to Iceland. It was about 9 a.m. on September 11, 2011 after a light snowfall. Temperatures were right around freezing. GPS on my camera gives the image location as 65.767733, -17.169181 and the altitude at 1,434 ft (437 m). This is just off the west side of the Holasandur volcanic sand desert in the island’s north. The mountain in the background is the Gaesafjoll volcano and the camera is facing east (ENE). I can say that it had been very windy for several days. On one of those days, we were on Breidamerkursandur, the black sand beach on Iceland's south coast. The wind was so strong it knocked me over. Down on the deck I was relentlessly buffeted by intensely blowing sand. When I stood up again I noticed that the sand was not blowing much higher than my knees. I wondered if something similar was going on with the snow. A strong wind, blowing consistently from upper left, might then explain the shadows. i.e., the snow-laden wind would carry streaks of load past the rock on either side, and the shadows would reflect simple interruptions in that sheet of blowing granular material. In the "close-up", you can see that the snow is pretty wet (though it need not have been so when it fell). Wet snow can still be redistributed if winds are sufficiently strong. Looking closely it appears that some of the "shadow" track have melted and then partially re-frozen with water glazing the surface. Click here or on the related link below for the details of other possibilities.

Photo details: Top - Camera Maker: HTC; Camera Model: PC36100; Focal Length: 4.9mm; ISO equiv: 117; Color Space: sRGB. Bottom - Camera Maker: Canon; Camera Model: Canon PowerShot SD1300 IS; Focal Length: 17.3mm; Aperture: f/5.6; Exposure Time: 0.0020 s (1/500); ISO equiv: 125; Exposure Bias: none; Metering Mode: Matrix; White Balance: Auto; Flash Fired: No (enforced); Orientation: Normal; Color Space: sRGB. Software: GIMP 2.6.1.

Lunar Corona and the Waxing Gibbous Moon

2012-01-31T03:01:00-05:00

Photographer: Laaifat Mohamed; Laaifat's Web site
Summary Author: Laaifat Mohamed; Jim Foster

The photo above showing a corona enshrouding the waxing gibbous Moon was observed above a lovely old church in Normandy, France. Jupiter is to the right of the Moon. Note the crescent shape of the clouds -- and the corona. The metallic colors of a corona results when minute water droplets that compose mid-level clouds are of the right size to deflect moonlight. The moonlight is bent and spread out by these tiny droplets in such a way to produce overlapping colors. Photo taken on December 7, 2011.