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Newsgroups: sci.astro, alt.sci.planetary, sci.physics, sci.geo.geology
From: "Robert Clark" <rgregorycl...@yahoo.com>
Date: 19 Oct 2006 04:19:10 -0700
Local: Thurs, Oct 19 2006 7:19 am
Subject: Re: A volcanic crater in Meridiani, Mars.

Robert Clark wrote:

The crater on the rim of Victoria crater on the right side of this
image very definitely gives the impression of a volcanic crater rather

Victoria Crater on Mars.
http://antwrp.gsfc.nasa.gov/apod/ap061002.html

An analogue of the Victoria crater complex might be Crater >Lake,

Crater Lake, Oregon
Crater Lake National Park
http://vulcan.wr.usgs.gov/Volcanoes/CraterLake/Locale/framework.html

A curious aspect of Victoria crater is its irregular rim with
alternating promontories and alcoves. The rim of Crater Lake, > Oregon

Crater Lake, Oregon.

Although in the case of Crater Lake, the irregular rim is only
apparent on half of the rim, the other half having a more >rounded

The volcanic crater on the rim of Victoria might be analogous >to

The crater forming Crater Lake formed from the collapse of a >volcano.
Then an analogous scenario would account for the origin of >Victoria

Then these two craters might give us a chance for the first >time to

Bob Clark

The hole looks outrageously deep and steep when you look at the
stereo image with 3-D glasses!

Layers of 'Cabo Frio' in 'Victoria Crater' (Stereo)
"This view of "Victoria crater" is looking southeast from "Duck Bay"
towards the dramatic promontory called "Cabo Frio." The small crater
in the right foreground, informally known as "Sputnik", is about 20
meters (about 65 feet) away from the rover, the tip of the
spectacular, layered, Cabo Frio promontory itself is about 200 meters
(about 650 feet) away from the rover, and the exposed rock layers are
about 15 meters (about 50 feet) tall. This is a red-blue stereo
anaglyph generated from images taken by the panoramic camera (Pancam)
on NASA's
Mars Exploration Rover Opportunity during the rover's 952nd sol, or
Martian day, (Sept. 28, 2006) using the camera's 430-nanometer
filters."

Bob Clark
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This was discussing the feature known as "Sputnik crater" on the edge
of Victoria crater at the Opportunity rover landing site.
Which of these two edges is the upper left edge of Sputnik crater?
What "standard" impact crater has two rims?

Cropped PANCAM image showing Sputnik crater.
http://bautforum.com/attachment.php?attachmentid=5715&d=1183252160

You see there is barely visible a raised rim around the perimeter of
the feature but the double edges at the upper left are exaggerated in
size compared to the rest of the rim.
I found something analogous to this in regards to volcanic vents in
this online lecture:

Pyroclastic Landforms and Pyroclasts.
http://skilling.geology.pitt.edu/GEO3975/pyroclastics/pyroclastics2.pdf

As shown in the image on p. 8 of this lecture, a blown up edge could
be due to wind driven ash from the vent:

"Diamond Head near Honolulu is a famously difficult phreatomagmatic
landform to slot into ring vs cone. Most of edifice resembles a tuff
ring, but wind has given rise to a steep cone-like side. Most of
deposits are also typical of tuff cones rather than rings. Hence
several factors control ring vs cone (hydrology, wind, efficiency of
magma-waterexplosions etc)."
PyroclasticLandforms and Pyroclasts, p. 8.

But what's really key in this lecture is discussion of the fact that
volcanic vents can have nested rims. See page 9 with an image of
Hanauma Bay, a nested tuff ring complex on the coast of Oahu and page
14 with "Asymmetric nested tuff cones of Koko Crater on Oahu".

Some more examples of "nested" volcanic craters:

Santa Ana Volcano.
"The summit of Santa Ana features four nested calderas and volcanic
craters, with the innermost containing a small crater lake."
http://en.wikipedia.org/wiki/Ilamatepec

Santa Ana Volcano, El Salvador.
"The volcano sports several crescent-like craters-"nested" craters-at
its summit and a 20-kilometer-long system of fissures."

This might be an especially relevant analog since it has a larger
volcanic crater nearby the nested crater that has a scalloped rim.
This would be analogous to the Victoria scenario if Victoria is a
volcanic collapse feature as I suggested.

Also:

Ibu, Halmahera, Indonesia.
"The nested sumit craters of Mt. Ibu. A brand new lava dome can be
seen within the central crater, emitting a plume of volcanic gases."

Global Volcanism Program | Volcanoes of the World | Types and
Processes Gallery | Craters.
Cotopaxi.
"The glacier-capped summit of Ecuador's Cotopaxi volcano is truncated
by two nested craters. The outer crater, seen here from the SE, is 800
x 550 m wide. A cone that grew inside this crater is cut by a smaller
crater that is 250 m wide and 120 m deep."
http://www.volcano.si.edu/world/tpgallery.cfm?category=Craters

Harrat Hutaymah, Saudi Arabia (Page 2 of 2).
"Looking northwest to the nested cinder and spatter cones of Harrat ad
Dakhana in the north-central part of the Harrat Hutaymah volcanic
field. Photo by Carl Thornber, U.S. Geological Survey."

Bob Clark

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Newsgroups: sci.astro, alt.sci.planetary, sci.physics, sci.geo.geology
From: "Robert Clark" <rgregorycl...@yahoo.com>
Date: 19 Oct 2006 04:19:10 -0700
Local: Thurs, Oct 19 2006 7:19 am
Subject: Re: A volcanic crater in Meridiani, Mars.

Robert Clark wrote:

The crater on the rim of Victoria crater on the right side of this
image very definitely gives the impression of a volcanic crater rather
than an impact crater:

Victoria Crater on Mars.
http://antwrp.gsfc.nasa.gov/apod/ap061002.html

An analogue of the Victoria crater complex might be Crater >Lake,
Oregon: