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.


Angle of Repose for Graupel

January 28, 2021

Image

Graupel4a

Photographer: Roger Hopkins
Summary Author: Roger Hopkins

The Nor’easter that visited the northeast U.S. on December 16-17,
2020, brought 13 inches (33 cm) of fine-grained graupel to Lansing,
New York, and an amazing 40 plus inches (100 cm) of snow and
graupel to Binghamton, about 40-miles (64 km) to the southeast. The
above photos show the angle of repose of these small uniform
graupel pellets as they accumulated on horizontal surfaces. Graupel
pellets bounce on impact and roll like tiny BBs off the edges of the
pile. After a few hours, the pellets within the pile can weld together
and as the height of the pile increases, fewer will land on the top,
creating a pointed witches hat shape. My measurements show an angle
of approximately 65 degrees. Note that the Avalanche Handbook and
other sources show values that range from 35 degrees to as high as 80
degrees.

The top photo (at left, courtesy of Scott Geiger of Binghamton) shows
his car with piled-up graupel that was still growing when the storm
abated, while the fence posts (at top right in Lansing) could only
sustain 3 inches (8 cm) high caps. The bottom photo illustrates the
interesting effect on a round rotating surface; two soda bottles
forming my squirrel barrier that will henceforth be called my snow
accumulation rotisserie.
* Lansing, New York Coordinates: 42.4842, -76.4799

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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 6 weeks, 1 day, 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.


Sunrise and Cloud Mirages Observed from Monte Tomba, Italy

April 28, 2021

2021_01_30 - Sunrise

Venturin - Sunrise 2

Photographer: Giacomo Venturin
Summary Authors: Giacomo Venturin; Jim Foster

Mock mirages at sunrise or sunset are quite common (top photo),
but one morning several weeks ago, while observing from Monte
Tomba, Cavaso del Tomba, Italy, I also saw cloud mirages (bottom
photo). This was a first for me. Initially, I didn't understand why the
clouds near the horizon looked so strange -- I thought my eyes were
focusing properly. Then I realized that the clouds were miraged as
well. When mirages are seen, temperature variations near the
surface must be sufficiently strong to enable light rays to bounce up
and down before reaching the observer’s eyes. Photos taken on February
16, 2021.
Photo Details: Canon 70/200 + 2x camera; Canon 60D lens; 400 mm; f/11;
100 ISO, 1/30 second exposure.
* Cavaso del Tomba, Italy Coordinates: 45.8700, 11.9032

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Cruise Ship Solar Halo and Lunar Halo Observed from Zsámbék,
Hungary
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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 2 weeks, 22 hours, 42 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.


Purple Anemone

May 28, 2021


Menashe_anemone_Picture3

Photographer: Menashe Davidson
Summary Author: Menashe Davidson

The main characteristic of the purple anemone flower is its
showiness. This is one flower you’ll always notice in the garden,
regardless of whatever is in bloom nearby. It belongs to the genus
anemone, comprised of over 200 species. The word “ anemone” is
derived from the Greek term "anemos" meaning winds. Thus, the purple
anemone is sometimes referred to as the windflower.

Flowers of the purple anemone tend to retire once the Sun goes down, a
phenomenon known as nyctinasty. On the montage pictured above, 4
stages are demonstrated in the anemone’s diurnal cycle. All photos
were taken in my home garden, in Rishon LeZion, Israel, on March 7,
2021. When the flowers are open, in addition to their delicate petals,
they expose their reproductive organs, illustrating a range of
shapes, colors and curves (bottom left).


Rishon LeZion, Israel Coordinates: 31.9730, 34,7925


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Plant Links

* Discover Life
* Tree Encyclopedia
* What are Phytoplankton?
* Encyclopedia of Life - What is a Plant?
* USDA Plants Database
* University of Texas Native Plant Database
* Plants in Motion
* What Tree is It?

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

https://epod.usra.edu

--- up 3 weeks, 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.


Lake Tahoe: Blue Gem of the Sierras

June 28, 2021

6a0105371bb32c970b026bded8df1a200c

Tahoe120c_7june21

Photographer: Ray Boren

Summary Author: Ray Boren

Straddling a state line shared by Nevada and California in the western
United States, beautiful Lake Tahoe is set like a gargantuan blue
gem in a high basin between the Sierra Nevada crest on the west
and the Sierras’ Carson Range spur on the east. In the first
photograph here, taken on June 7, 2021, the panoramic perspective to
the south and southwest is from a high viewpoint above the north
shore’s Incline Village, along Nevada’s Mount Rose Highway (State
Route 431). A second photo, taken the same day, presents a shoreline
view from Lake Tahoe’s north-shore resort town of Kings Beach,
California.

Tahoe’s name is an anglicization of a Native American Washoe tribal
term describing “The Lake,” “Big Water,” or “Water in a High Place” —
all quite apt. Tahoe is the largest fresh-water alpine lake in
North America, covering 122,616 acres (49,621 hectares). With a depth
of 1,645 feet (501 m), it is also the second-deepest in the United
States (behind Oregon’s lovely Crater Lake). It is 22 miles (35 km)
long, north to south, and 12 miles (19 km) at its widest, with 72 miles
(116 km) of shoreline.

Basin-and-range faulting is credited with forming a series of
west-tilted blocks and east-dipping faults that produced the
north/south trending basin about 2 million years ago. Elevations at
Tahoe range from 6,225 feet (1897 m) at lake level to 10,891 feet (3320
m) atop Freel Peak. The spectacular and pleasing natural beauty of
today’s Lake Tahoe basin is the result of manifold geological processes
over millions of years, the Geologic Survey notes, including marine
deposition, granitic intrusion, tectonic uplift, volcanic eruptions,
and ice-age glacial scouring and other forms of erosion.
* Lake Tahoe Coordinates: 39.092, -120.033

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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 7 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.


Archive - Erta Ale, Ethiopia

August 28, 2021

6a0105371bb32c970b01b7c768d93c970b
Every weekend we present a notable item from our archives.
This EPOD was originally published April 7, 2015.

Photographer: Joel Santos
Summary Author: Joel Santos April 2015 Viewer's Choice

Erta Ale is a continuously active, basaltic shield
volcano in the Afar Region of northeastern Ethiopia. Its
caldera is notable for holding one of world's longest-existing
lava lakes -- first reported in 1906. Volcanoes with lava lakes are
quite rare. Only six are known worldwide. The nearly full Moon, on
the rise this early January night, illuminates the low clouds, acting
to balance the light of the sky with the strong orange light of the
bursting lava. Photo taken on January 10, 2015.

Photo details: Fisheye lens; 8-15 mm; 85 sec exposure; f/4; ISO 400.
* Erta Ale, Ethiopia Coordinates: 13.599722, 40.659722

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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

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

https://epod.usra.edu

--- up 16 weeks, 1 day, 12 hours, 15 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (21:1/186)