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APOD: A Triangular Shadow of a Large Volcano (2019 Jun 09)
Posted: Sun Jun 09, 2019 4:11 am
by APOD Robot
A Triangular Shadow of a Large Volcano
Explanation: Why does the shadow of this volcano look like a triangle? The
Mount Teide volcano itself does not have the strictly
pyramidal shape that its geometric shadow might suggest. The
triangle shadow phenomena is not unique to the
Mt. Teide, though, and is
commonly seen from the tops of other
large mountains and volcanoes. A key reason for the strange dark shape is that the observer is looking down the long corridor of a sunset (or sunrise) shadow that extends to the horizon. Even if the
huge volcano were a perfect
cube and the resulting shadow were a long rectangular box, that box would appear to taper off at its top as its
shadow extended far into the distance, just as parallel
train tracks do. The featured spectacular image shows
Pico Viejo crater in the foreground, located on
Tenerife in the
Canary Islands of
Spain. The nearly full moon is seen nearby shortly after its
total lunar eclipse.
Re: APOD: A Triangular Shadow of a Large Volcano (2019 Jun 09)
Posted: Sun Jun 09, 2019 8:45 am
by Ann
This is a spectacular image with rich deep colors and a fantastic optical effect.
Ann
Re: APOD: A Triangular Shadow of a Large Volcano (2019 Jun 09)
Posted: Sun Jun 09, 2019 11:40 am
by De58te
I don't think that perspective isn't the only explanation for the triangle shape. Unlike railroad tracks, I don't think many volcanoes have parallel cube shape sides. I think that volcanoes are mostly cone shaped with the wider part at the base. Now a cone pictured in two dimensions looks like a triangle. Now why a volcano takes on a cone shape is physics due to fluid flow in gravity. Unlike solids an erupting lava flow would flow down the sides of a volcano because it is fluid. When it gets to the bottom it cools and then turns solid. Solids then usually don't move anymore and stay in place. As time goes on and more fluid lava flows it tends to bunch up at the bottom so then an old volcano tends to have much more mass at the bottom than the top and so it shapes like a cone.
Re: APOD: A Triangular Shadow of a Large Volcano (2019 Jun 09)
Posted: Sun Jun 09, 2019 11:43 am
by orin stepanek
Nice! I thought there was a similar one where the moon was within the shadow!
Re: APOD: A Triangular Shadow of a Large Volcano (2019 Jun 09)
Posted: Sun Jun 09, 2019 12:09 pm
by neufer
orin stepanek wrote: ↑Sun Jun 09, 2019 11:43 am
Nice! I thought there was a similar one where the moon was within the shadow!
https://apod.nasa.gov/apod/ap190310.html
http://asterisk.apod.com/viewtopic.php? ... 7&p=290556
Re: APOD: A Triangular Shadow of a Large Volcano (2019 Jun 09)
Posted: Sun Jun 09, 2019 3:05 pm
by orin stepanek
Thanks Art; That's the one!
Oh; Guess I should have clicked on commonly seen in the write up!
Re: APOD: A Triangular Shadow of a Large Volcano (2019 Jun 09)
Posted: Sun Jun 09, 2019 3:24 pm
by rustybrown@live.ca
The triangle shadow phenomena is not unique...
It's a phenomenon, really.
Just to clarify.
Re: APOD: A Triangular Shadow of a Large Volcano (2019 Jun 09)
Posted: Sun Jun 09, 2019 5:10 pm
by neufer
rustybrown@live.ca wrote: ↑Sun Jun 09, 2019 3:24 pm
The triangle shadow phenomena is not unique...
It's a phenomenon, really.
Just to clarify.
https://www.etymonline.com/search?q=phenomenon wrote:
phenomenon (n.) 1570s, "fact, occurrence," from Late Latin phænomenon, from Greek phainomenon "that which appears or is seen," noun use of neuter present participle of phainesthai "to appear," passive of phainein "bring to light, cause to appear, show." Meaning "extraordinary occurrence" first recorded 1771. Plural is phenomena.
..........................................................
phenomenal (adj.) 1803, "of the nature of a phenomenon," a hybrid from phenomenon + -al. Meaning "remarkable, exceptional" is from 1850.
[Phenomenal] is a metaphysical term with a use of its own. To divert it from this proper use to a job for which it is not needed, by making it do duty for remarkable, extraordinary, or prodigious, is a sin against the English language. [Fowler]
MoonRise Through Mount Teide's Shadow; © Casado (TWAN)
Posted: Sun Jun 09, 2019 9:48 pm
by JKent@APD
Been there Done That!
MoonRise Through Mount Teide's Shadow; © Casado (TWAN)
A Triangular Shadow of a Large Volcano
Image Credit & © Juan Carlos Casado (TWAN)
Why does the shadow of this volcano look like a triangle? The Mount Teide
volcano itself does not have the strictly pyramidal shape that its geometric
shadow might suggest. The triangle shadow phenomena is not unique to the Mt.
Teide, though, & is commonly seen from the tops of other large mountains &
volcanoes. A key reason for the strange dark shape is that the observer is
looking down the long corridor of a sunset (or sunrise) shadow that extends to
the horizon. Even if the huge volcano were a perfect cube & the resulting
shadow were a long rectangular box, that box would appear to taper off @ its
top as its shadow extended far into the distance, just as parallel train
tracks do. The above spectacular image shows Pico Viejo crater in the
foreground, located on Tenerife in the Canary Islands of Spain. The nearly
full moon is seen nearby shortly after its total lunar eclipse last month.
