EPOD - a service of USRA

The Earth Science Picture of the Day (EPOD) highlights the diverse processes and phenomena which shape our planet and our lives. EPOD will collect and archive photos, imagery, graphics, and artwork with short explanatory
captions and links exemplifying features within the Earth system. The
community is invited to contribute digital imagery, short captions and
relevant links.


Inferior Mirage Observed from Plemmirio, Syracuse, Italy

February 12, 2021

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Photographer: Kevin Saragozza
Summary Author: Kevin Saragozza

Mirages are quite common and very fascinating phenomena. Their
mechanism of formation is a consequence of the laws of geometric
optics, especially refraction. We can distinguish mirages into two
main classes; superior (upper) mirages and inferior (lower)
mirages. An example of an inferior mirage, the type most often seen, is
what looks to be wet asphalt on the road ahead of us on a hot summer’s
day. What we’re seeing, in fact, is nothing more than the refracted
image of the sky. On the photo above, taken near Plemmirio, Syracuse,
Italy, we’re able to see the distant town of Portopalo di Capo Passero
floating on the horizon, even though it’s some 25 miles (40 km) away.
Of course, in the absence of this inferior mirage, we wouldn’t be able
to see this far.

Mirages are formed in the presence of rather intense air
temperature gradients -- an abrupt temperature variation between nearby
air layers. When the temperature decreases very rapidly as the height
above the ground increases, the density of the air changes just as
rapidly. Because of this, a light ray no longer propagates in a
straight line but is bent upwards and forms a lower mirage. As a
result, an object appears lower than it is in reality, hence the name
inferior mirage. Photo taken on December 13, 2020 (15:49 local time).

Photo Details: Canon Eos R camera; + 70-200 2.8 lens; f9; 1/500 sec.
exposure; ISO100
* Plemmirio, Italy Coordinates: 37.0054, 15.3175

Related EPODs

Inferior Mirage Observed from Plemmirio, Syracuse, Italy
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Nags Head, North Carolina Lunar Halo Above Evia, Greece Bright
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Atmospheric Effects Links

* Atmospheric Optics
* Color and Light in Nature
* The Colors of Twillight and Sunset
* Refraction Index
* Image Gallery: Atmospheric Effects
* What is a Rainbow?

-
Earth Science Picture of the Day is a service of the Universities
Space Research Association.

https://epod.usra.edu

--- up 8 weeks, 2 days, 21 hours, 27 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (21:1/186)

EPOD - a service of USRA

The Earth Science Picture of the Day (EPOD) highlights the diverse processes and phenomena which shape our planet and our lives. EPOD will collect and archive photos, imagery, graphics, and artwork with short explanatory
captions and links exemplifying features within the Earth system. The
community is invited to contribute digital imagery, short captions and
relevant links.


Capo Murro di Porco Lighthouse and Maddalena Peninsula

January 12, 2021

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Photographer: Kevin Saragozza
Summary Author: Kevin Saragozza
Shown above at center is the picturesque Capo Murro di Porco
Lighthouse on the Maddalena Peninsula of Sicily, Italy. The steep
cliffs of this peninsula, which formed from a tectonic fault
feature known as a horst, drop abruptly (175 ft or 54 m) to the
sea. Exposed rocks are generally calcareous (limestone).

Overhead, mid-level altocumulus clouds spread across the western
sky. As shown here, they’re illuminated from below by the grazing light
of the setting Sun. Photo taken on November 8, 2020.
Photo Details: Sony a7iii+ camera; Sony 16 35; f4; overview consisting
of 5 shots combined with raw camera (F10 / 10-second exposure; ISO 125)
* Plemmirio, Italy Coordinates: 37.003119, 15.335129

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Capo Murro di Porco Lighthouse and Maddalena Peninsula Sherwin
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Geography Links

* Atlapedia Online
* CountryReports
* GPS Visualizer
* Holt Rinehart Winston World Atlas
* Mapping Our World
* Perry-Castañeda Library Map Collection
* Types of Land
* World Mapper

-
Earth Science Picture of the Day is a service of the Universities
Space Research Association.

https://epod.usra.edu

--- up 3 weeks, 6 days, 21 hours, 27 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (21:1/186)

EPOD - a service of USRA

The Earth Science Picture of the Day (EPOD) highlights the diverse processes and phenomena which shape our planet and our lives. EPOD will collect and archive photos, imagery, graphics, and artwork with short explanatory
captions and links exemplifying features within the Earth system. The
community is invited to contribute digital imagery, short captions and
relevant links.


Helical Clouds

March 12, 2021

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Photographer: Nelson Reticence
Summary Authors: Nelson Reticence; Jim Foster
These eye-catching clouds were observed over Holyoke,
Massachusetts, at sunset on November 24, 2020. Looking like helical DNA
strands or breaking waves, they form where the layer of air that
contains the clouds moves at a different velocity and has a
different density than the air in the layer just above the clouds. This
results in air flows that tend to have a distinct serpentine
motion.
* Holyoke, Massachusetts Coordinates: 42.2043, -72.6162

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Archive - Virga and Rays Sunrise Mammatus Clouds
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Cloud Links

* Atmospheric Optics
* The Cloud Appreciation Society
* Cloud Atlas
* Color and Light in Nature

-
Earth Science Picture of the Day is a service of the Universities
Space Research Association.

https://epod.usra.edu

--- up 12 weeks, 2 days, 21 hours, 27 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (21:1/186)

EPOD - a service of USRA

The Earth Science Picture of the Day (EPOD) highlights the diverse processes and phenomena which shape our planet and our lives. EPOD will collect and archive photos, imagery, graphics, and artwork with short explanatory
captions and links exemplifying features within the Earth system. The
community is invited to contribute digital imagery, short captions and
relevant links.


Backyard Avalanche

April 12, 2021

Pre-Avalanche (1)

Photographer: George Seielstad
Summary Authors: George Seielstad; Jim Foster
Seldom does an avalanche occur on your outside deck, but conditions
in February of 2021 created one at my home in western Montana. A snowy
start to the month was followed by continuously cold weather through
mid-February when only on one day did the thermometer reach freezing
(32 F or 0 C).

Shown above is a glass-topped table with rounded edges having a slight
tilt. After snow piled up on the table, a meltwater lens allowed the
load to gradually slide slowly off the downhill edge. Notice how
the curved edge is rounded on the underside of the table. This
demonstrates snow's substantial tensile strength. Photos taken on
February 19, 2021.
* Missoula, Montana Coordinates: 46.872, -113.9940

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Cryosphere Links

* Guide to Frost
* What is the Cryosphere?
* Bentley Snow Crystals
* Glaciers of the World
* Ice, Snow, and Glaciers: The Water Cycle
* The National Snow and Ice Data Center Google Earth Images
* Snow and Ice Crystals

-
Earth Science Picture of the Day is a service of the Universities
Space Research Association.

https://epod.usra.edu

--- up 2 weeks, 3 days, 22 hours, 10 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (21:1/186)

EPOD - a service of USRA

The Earth Science Picture of the Day (EPOD) highlights the diverse processes and phenomena which shape our planet and our lives. EPOD will collect and archive photos, imagery, graphics, and artwork with short explanatory
captions and links exemplifying features within the Earth system. The
community is invited to contribute digital imagery, short captions and
relevant links.


Omega Sun over South Padre Island, Texas

May 12, 2021

Omega Sunset

Photographer: César Cantú
Summary Authors: César Cantú; Jim Foster
The photo above was captured at sunset over the Gulf of Mexico, as
viewed from South Padre Island, Texas. Because of strong
atmospheric refraction the solar disk takes the shape of the Greek
letter omega.

At sunset or sunrise, sunlight directed towards us from the lower
portion of the Sun passes through a somewhat denser atmosphere than
rays coming from the Sun’s upper limb. Consequently, the bottom of the
solar disk is refracted more, and thus distorted more, than the top
of the solar disk. The omega shape (also known as Etruscan vase)
actually results from an inferior mirage. When the Sun drops beneath
the horizon, its inferior mirage seems to connect with the true
Sun.

A wind turbine for generating electric power is in the foreground.
Photo taken on March 6, 2021.

South Padre Island, Texas Coordinates: 26.1118, -97.1681


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Islands (Spain) and Paris, France Cloud Corona Above Syracuse,
Italy
More...

Atmospheric Effects Links

* Atmospheric Optics
* Color and Light in Nature
* The Colors of Twillight and Sunset
* Refraction Index
* Image Gallery: Atmospheric Effects
* What is a Rainbow?

-
Earth Science Picture of the Day is a service of the Universities
Space Research Association.

https://epod.usra.edu

--- up 5 days, 12 hours, 15 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (21:1/186)

EPOD - a service of USRA

The Earth Science Picture of the Day (EPOD) highlights the diverse processes and phenomena which shape our planet and our lives. EPOD will collect and archive photos, imagery, graphics, and artwork with short explanatory
captions and links exemplifying features within the Earth system. The
community is invited to contribute digital imagery, short captions and
relevant links.


Archive - Red Rose and Morning Dew

June 12, 2021

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Happy Red Rose Day! Each weekend we present a notable item from our
archives. This EPOD was originally published May 12, 2013.

Photographer: Alejandro Jaramillo
Summary Authors: Alejandro Jaramillo; Jim Foster
The photo above showing a red rose draped in dewdrops was taken
in Medellin, Colombia. When air at a constant atmospheric
pressure is cooled below its dew point, typically in the early
morning hours, moisture condenses not only on blades of grass and
windshields but on all nearly all exposed surfaces. In fact, many
plants, and even some animals, rely on dew and fog as a valuable
source of water.
The dipole charge on every water molecule attracts them to each
other -- positive to negative and negative to positive. Water drops are
more or less spherical because of this electrostatic attraction and
cohesion. Photo taken on May 3, 2012.
Photo details: SONY NEX-5N camera; 54 mm focal length; f/5 aperture;
1/100 sec. exposure; ISO 200.
* Medellin, Colombia Coordinates: 6.2457, -75.5822

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Atmospheric Effects Links

* Atmospheric Optics
* Color and Light in Nature
* The Colors of Twillight and Sunset
* Refraction Index
* Image Gallery: Atmospheric Effects
* What is a Rainbow?

-
Earth Science Picture of the Day is a service of the Universities
Space Research Association.

https://epod.usra.edu

--- up 5 weeks, 1 day, 12 hours, 15 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (21:1/186)

EPOD - a service of USRA

The Earth Science Picture of the Day (EPOD) highlights the diverse processes and phenomena which shape our planet and our lives. EPOD will collect and archive photos, imagery, graphics, and artwork with short explanatory
captions and links exemplifying features within the Earth system. The
community is invited to contribute digital imagery, short captions and
relevant links.


Peering Into the Geology of Central Aragón

July 12, 2021

Aliaga

Photographer: Martin Ripsam

Summary Author: Martin Ripsam & Cadan Cummings

Taken from the viewpoint of the Geological Park of Aliaga (Aragon,
Spain), this picture shows the tectonic history of Central Aragon.
Located in eastern Spain, the landscape around Aliaga contains rocks
from all the geologic ages for the last 200 Million years, mostly
Mesozoic and Cretaceous limestones. One of the most well-known
landforms of this region is the Camarillas Formation situated just
outside the town of Aliaga. Geologically, this area is majority
comprised of sandstone, limestone, mudstone, and conglomerates
deposited in lacustrine and fluvial ecosystems hundreds of
millions of years ago when the land that is now the Iberian
Peninsula was separated from the rest of Europe by seas.
* Aliaga, Spain Coordinates: 40.66715, -0.71776

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Geology Links

* Earthquakes
* Geologic Time
* Geomagnetism
* General Dictionary of Geology
* Mineral and Locality Database
* Mohs Scale of Mineral Hardness
* This Dynamic Earth
* USGS
* USGS Ask a Geologist
* USGS/NPS Geologic Glossary
* USGS Volcano Hazards Program

-
Earth Science Picture of the Day is a service of the Universities
Space Research Association.

https://epod.usra.edu

--- up 9 weeks, 3 days, 12 hours, 15 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (21:1/186)

EPOD - a service of USRA

The Earth Science Picture of the Day (EPOD) highlights the diverse processes and phenomena which shape our planet and our lives. EPOD will collect and archive photos, imagery, graphics, and artwork with short explanatory
captions and links exemplifying features within the Earth system. The
community is invited to contribute digital imagery, short captions and
relevant links.


Willow Falls Near Hudson, Wisconsin

August 12, 2021

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Photographer: Dale Hugo

Summary Author: Dale Hugo

This photo is of the fantastic Willow Falls in the Willow River
State Park located near Hudson, Wisconsin. The waterfall is
approximately 100 ft wide (30.5 m) and consist of multiple smaller
tiers, with the largest being around 15 ft (4.5 m) tall. Part of the
wider 62-mile long Wilow River, the riverway serves as a tributary
to the St. Croix River that largely defines the Wisconsin-Minnesota
border. As you see in the picture, the falls are stepped in between
dolomitic limestone cliffs. Geological studies have examined the
surrounding limestone formations and concluded the oldest rock samples
date back to the Cambrian Period of the Paleozoic Era.

Although the falls consist of several tiered drop offs, the river is
very accessible, and many people enjoy walking in the river as well as
on the bridge and surrounding trails. We happened to arrive around noon
when the sunlight was streaming into the canyon and illuminating the
area beautifully. It also helped to visit near the summer solstice
because the high Sun angle gave the water a sparkling appearance.
* Hudson, Wisconsin Coordinates: 45.019644, -92.675808

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More...

Geology Links

* Earthquakes
* Geologic Time
* Geomagnetism
* General Dictionary of Geology
* Mineral and Locality Database
* Mohs Scale of Mineral Hardness
* This Dynamic Earth
* USGS
* USGS Ask a Geologist
* USGS/NPS Geologic Glossary
* USGS Volcano Hazards Program

-
Earth Science Picture of the Day is a service of the Universities
Space Research Association.

https://epod.usra.edu

--- up 13 weeks, 6 days, 12 hours, 15 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (21:1/186)