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 - Explaining Ring Patterns in a Frozen Puddle

January 26, 2020

IceRingsIMG_2777 (2)
Each Sunday we present a notable item from our archives. This EPOD was
originally published January 28, 2014.
Photographer: Douglas Stith
Summary Authors: Douglas Stith; Steven Arcone; Zachary Stith
My son, Zachary, found this curious frozen puddle in Concord, New
Hampshire on the afternoon of February 1, 2013. January 31 had
unseasonably warm temperatures (in the 50’s F, about 12 C) and heavy
rain, but temperatures plummeted after sundown. The official morning
temperature on February 1 was 16 F (-9 C), but the temperature was
still well below freezing later in the day. The puddle’s diameter was
approximately 6 ft (2 m). Upon closer inspection, we found that the
ice wasn't completely frozen to the puddle's shallow bottom. We
easily picked up the thin frozen layers on the puddle that were no more
than about a quarter-inch (5 mm) thick. We also observed slight bulges
below the rings of ice. The overall milky-white color resulted from the
presence of minute air bubbles, but some clear bubbles were also
present.
How various ice features form, change shape and melt is rarely
straightforward and sometimes quite confounding. Factors such as water
purity, the rate of cooling, the preferred growth of ice in crystalline
planes, etc., all play a role.
The shallowness of this puddle suggests that it rapidly froze; only a
thin water layer remained below the puddle. Then the fast-falling
temperatures likely caused the ice to contract, which produced the
cracking. Continued cooling widened the cracks. The ring pattern shows
that the main direction of the stress force was radial, but the
scalloped pattern along the rings shows that some stress varied with
angle around the center. The small amount of water that didn't freeze
rose into the cracks due to the hydrostatic pressure of the ice
above and capillary action. Water in the rings then froze and
expanded, and as it did it widened the rings and also directed the
remaining small amount of liquid to the top of the ice. The slight
bulges on the bottom of the rings were remnants of its last contact
with the deepest water. In other words, the unfrozen water at the
bottom of the puddle was, in essence, pushed and suctioned into the
cracks.

Photo Details: Camera: Canon PowerShot SX120 IS; Lens: 6.0-60.0 mm;
Focal Length: 6mm; Aperture: f/2.8; Exposure Time: 0.033 s (1/30); ISO
equiv: 250.
* Concord, New Hampshire Coordinates: 43.2067, -71.5381

Related EPODs

Archive - Explaining Ring Patterns in a Frozen Puddle Encore -
Snow Eyes Icy Drops Snow Blankets Joshua Tree National Park
Encore - Lake Michigan Ice Cave Hexagonal Plate Snow Crystal
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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 4 days, 15 hours, 4 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.


Narcissus and Cyclamen

February 26, 2020

Cylcamen_Picture2

Photographer: Menashe Davidson
Summary Author: Menashe Davidson

Menashe_Picture3 Many people living in Israel celebrate the winter
season by traveling to their favorite locations in order to see the
beautiful wildflowers that appear after the first rains of the new
year. Narcissus (top photo) is closely related to the daffodil
and is a common wildflower in Israel. It’s known here as the
king of the swamp. Cyclamen (bottom photo) like narcissus,
grows all across the country. Both are the wild ancestors of cultivated
varieties that were selected for their showy, colorful flowers and
their ornamental value.

It's very rewarding to able to bring nature home. The photo at left
shows narcissus (foreground) and cyclamen (background) as
ornamental cultivars, grown in my apartment garden in Rishon
LeẔiyyon, Israel. Not surprisingly, this narcissus found a way to be
the center of attention. Top and bottom photos taken in January 2020;
inset photo taken on February 1, 2020.
* Rishon LeẔiyyon, 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 5 weeks, 15 hours, 5 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.


Flower-head of Cockscomb

March 26, 2020

Cockscomb

Cockscomb2

Photographer: Menashe Davidson
Summary Author: Menashe Davidson

The cockscomb ( Celosia argentea cristata) belongs to the
amaranth family, Amaranthaceae. The flower's name comes from the
bloom's head resemblances to a rooster's comb. When in bloom, the
flattened fan-shaped flower-head consists of hundreds of tiny
individual flowers that grow on both sides of the bloom's fringe.
Looking at it from above, the folded shape of the fringe appears as one
big flower with many hairs growing out, about 2-3 mm in length (top
photo).

A closer view below the head, (bottom photo) shows small, individual
flowers growing at the base of the fringe. These flowers are lighter
colored than the ones positioned higher up -- they bloom from bottom to
top. If you look carefully, you may be able to distinguish stamens
and pistils in the flowers open end. Note also the tightly packed,
torpedo-shaped buds just below the fringe. Photos were taken on
September 16, 2019, from my home garden in Rishon LeẔiyyon, Israel,
Israel. This is a video in which I touch the coronavirus threat and
my place of refuge, full with bloom.
* Rishon LeẔiyyon, Israel Coordinates: 31.9730, 34.7925

Related EPODs

Flower-head of Cockscomb Favagello Buttercup Narcissus and
Cyclamen Bosco di Santo Pietro Natural Reserve Nature Nurturing
Nature: Stump Flowerpots Chrysanthemums
More...

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 9 weeks, 1 day, 14 hours, 5 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.


Baboon’s Tail

June 26, 2020

BaboonsTail_DSC03902 (002)

BaboonsTail2_DSC05869 (002)

Photographer: Patti Weeks
Summary Author: Patti Weeks

The deciduous perennial shrub baboon’s tail
( Xerophyta retinervis) sometimes looks like a cluster of blackened
dead stumps, but at this point it is simply in a state of dormancy.
Named of course for its resemblance to a baboon’s tail, this shrub
has other common names: monkey’s tail, resurrection plant and
black stick lily. There are approximately 50 species of this
genus, including nine in South Africa. This knee-high plant is very
tough and can survive long periods of drought, as has the one in these
photos, taken December 14, 2019, in South Africa’s Waterburg region
in the province of Limpopo. South Africa has been suffering from
this drought since 2018. The shrub can go years without blooming,
but in the right conditions, it will sprout long, linear leaves and can
produce lovely pink, mauve or white flowers. After a rain, it can
resume its metabolic function within 48-72 hours. Scattered in open
areas, these shrubs stabilize sandy soil.
Ranger Barend van Rooyen of the Nedile Lodge in the Welgevonden
Game Reserve, shows my safari tour group the overlapping, wiry fibers
in one of the stout stems, which are tight but can be fanned open. He
tells us that since the stems resist burning, ancient bushmen
would put smoldering hot coals inside the fibers to transport them from
one village to the next.
According to an online source of the South African National
Biodiversity Institute, various parts of the shrub have been used
traditionally for their medicinal properties, from relieving asthma to
acting as an anti-inflammatory or analgesic. The tough stems have also
been used traditionally to make brushes and mats. European settlers
used the stems to make scrubbing brushes. In unprotected areas baboon’s
tail shrubs are gathered illegally to make bases for epiphytic orchids;
however, nurseries are able to propagate the shrub by seed for this
purpose.

Photo Details: Top - SONY DSC-RX10 IV camera; 151.11 mm focal length;
f/4; 1/200 second exposure; ISO 800. Bottom - Same except 49.51 mm
focal length; f/4; 1/417 sec. exposure; ISO 100
* Waterberg, South Africa Coordinates: -24.7, 28.4

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More...

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 22 weeks, 2 days, 16 hours, 4 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 - Concretions

July 26, 2020

Concretions

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

Provided by: Steve Kluge, Fox Lane High School
Summary authors & editors: Bill Cordua; Peter Mozley; Steve
Kluge

Concretions are hard masses of sedimentary and, more rarely, volcanic
rock that form by the preferential precipitation of minerals
(cementation) in localized portions of the rock. They're commonly
sub-spherical but frequently form a variety of other shapes, including
disks, grape-like aggregates and complex shapes that defy description.
Concretions are usually very noticeable features because they have a
strikingly different color and/or hardness than the rest of the rock.
In some areas this is unfortunate as the concretions have attracted the
unwanted attention of local graffiti artists. Commonly, when you break
open concretions you'll find that they have formed around a nucleus,
such as a fossil fragment or piece of organic matter. For a variety of
reasons, this nucleus created a more favorable site for cement
precipitation than other sites in the rock.

The 2 m by 3 m sandstone concretion on the left of the above photo
(taken in October 2002) was sliced nicely in half by the excavation of
the I-70 roadcut through the Dakota Hogback, west of Denver, Colorado.
This particular outcrop is easily reached by a short hike along the
geology trail on the south side of the highway. Another smaller but
whole concretion is exposed south of here where Alameda Drive crosses
Dinosaur Ridge. In this area, the rocks of the Dakota Formation also
preserve numerous dinosaur track-ways in the rippled and petrified
sands of an early Cretaceous shoreline (see Earth Science Picture
of the Day for May 12, 2003). The photo on the right was taken in June
1984. It shows Bill Cordua standing by a large septarian concretion,
one of the Moeraki Boulders. These boulders are found on the beach
along the east coast of South Island, New Zealand (between the towns of
Moeraki and Hampton). This area is a scientific preserve. The
concretions are weathering out of Paleocene mudstones and may reach 2 m
in diameter. It's estimated that the largest of these concretions took
about 4 million years to grow.


Related EPODs

Archive - Concretions Archive - Diamond Hunt Archive -
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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 1 week, 3 days, 15 hours, 25 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.


Reynisfjara Beach, Iceland

August 26, 2020

DSC_3580

Photographer: Salvatore Cerruto
Summary Author: Salvatore Cerruto

One of the many geological wonders on the island of Iceland is the
black sand of Reynisfjara beach, on a volcanic bay in the south
of Iceland. This beach is often on lists of the most beautiful beaches
of the world. The sand here is derived from weathered basalt.

Basalt columns, best seen at upper right, form as iron and
magnesium-rich basalt lava cools and contracts. Once exposed to the
surface air it hardens and solidifies. Generally, the fracture pattern
begins at the cooler surface and is propagated downward as the
cooling process spreads, forming long, geometric — and usually
hexagonally shaped — columns of rock. To me, this rock formation
resembles a fallen dragon, one of the majestic beasts sometimes
associated with fantasy films on exotic islands like Iceland. Photo
taken on September 25, 2017.
* Reynisfjara Beach, Iceland Coordinates: 63.4030577, -19.0426247

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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 1 day, 20 hours, 20 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.


Schöllenen Gorge

October 26, 2020

Schöllenen Gorge and the Devil’s Bridge

Photographer: Michela Meda
Summary Author: Michela Meda; Stu Witmer

The Schöllenen Gorge, shown above, is an excellent place to see the
effects of the collision of the African and European
tectonic plates. It’s located in the canton of Uri, Switzerland,
between the municipalities of Göschenen in the north and Andermatt in
the south. The gorge is situated on the Ruess River in the southern
part of the Central Aar Granite, a granitic batholith that
intruded about 300 million years ago. Up to 1,968 ft (600 m) in
depth, the gorge shows the fracture systems brought about primarily
by uplift and shear as the continents moved together.

An impediment to travel throughout human history, bridges have been
built across the gorge since the 13th century. The first stone bridge,
called the Devil's Bridge, was built about 1585. Photo taken August
11, 2020.

Photo Details: Pentax K5 and Smartphone Huawey P20 Lite
* Schöllenen Gorge, Switzerland Coordinates: 46.647236, 8.590465

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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 8 weeks, 6 days, 20 hours, 20 minutes
* Origin: -=> Castle Rock BBS <=- Now Husky HPT Powered! (21:1/186)