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Andre

Coronae surprise

Coronae are circular to elliptical features marked by a ring of concentric ridges, and are thought to result from the flow of heat in the planet's interior. abundant on Venus but also thought to be unique for Venus.

So where are these coronae?



In the Sahara!

Paste into the Google Earth "fly-to" cell:

18.82934722N 8.769259259E

and then zoom out to about 100 kilometers altitude.

Any thoughts?

Download Google Earth.
Matt

Near as I can tell this is the "timia jurassic granite ring complex" which I would presume are granite batholiths that have been exposed by erosion. See http://links.jstor.org/sici?sici=0020-2754(196909)1%3A47%3C25%3ASAOTGO%3E2.0.CO%3B2-B (the board's bbcode seems not to like the link so you'll have to copy-paste.

I'll have to wait til I'm next in university to view the full version.

The large circular fracture independant of the rock masses is interesting. Perhaps faulting caused during uplift, or some type of ring dyke.
Matt

Quote:
The Air Mountains make up one of the largest ring dike structures in the world. This Precambrian massif is famous for magmatic ring complexes 50 miles (80 km) in diameter. Ring-dikes, stocks and batholiths run 342 miles (550 km) from north to south.


http://volcano.und.nodak.edu/vwdocs/volc_images/africa/air.html
Matt

Me again! This topic has caught my interest somewhat as I'd never heard of these coronae before.

From my reading they seem to be analagous to hot spot swells:
Quote:
They have positive topographic expressions, with a surrounding moat or trough, and typical heights of more than 2 km above the surrounding plains.
(snip)
The interiors of most coronae contain numerous, smaller volcanic features, such as lava flows, calderas, shield volcanoes, domes, and lava channels.

Source

If these are hotspots, the difference between them could be due to Earth having moving tectonic plates and Venus not doing. Where on Earth we get a hotspot track, there would be prolonged focused activity on Venus. Venus also seems not to be subject to much surface erosion so features that would be worn down on earth may persist for much longer.

If they are an equivalent to hotspots then there seems to be relatively little volcanism though... Maybe melt is less easily produced for some reason.


Either way, they bare little to no resemblance to the Air mountains.
billiards

So if they are upwelling due to buoyant material beneath, what causes the compressional ridges to form?

If they are erosional features, it would be interesting to know, how much erosion do you get on Venus?

Are these features on Earth the really same thing (i.e. formed by similar processes) as the coronae on Venus?

These circular regions are called coronae. Coronae can vary in size from 60 to 1060 km across and are also unique to Venus. (Image credit: NASA)

The measurement tool on google earth revealed that these features in Africa are typically about 10 - 40 km across, so they are much smaller than the features seen on Venus. This leads me to suspect that they are probably not true Coronae.
Latecommer

I remember reading an alternative hypothesis to hot spot tracks recently, but can't put my finger on where. Perhaps in a journal, perhaps in one of the forums I frequent. Can anyone help me out here?
NileQueen

Latecommer wrote:
I remember reading an alternative hypothesis to hot spot tracks recently, but can't put my finger on where. Perhaps in a journal, perhaps in one of the forums I frequent. Can anyone help me out here?

http://www.mantleplumes.org

and

http://geology.about.com/library/weekly/aa011401a.htm
A Hotspot alternative
Mk

billiards wrote:

These circular regions are called coronae. Coronae can vary in size from 60 to 1060 km across and are also unique to Venus. (Image credit: NASA)

The measurement tool on google earth revealed that these features in Africa are typically about 10 - 40 km across, so they are much smaller than the features seen on Venus. This leads me to suspect that they are probably not true Coronae.

Who says we can't have smaller coronae?
Latecommer

Thank you Nile Queen for the helpful sites.
Now having a working idea of plume theory, I ask, what do you think about this theory?
Could it be possible that is just one of the ways islands are formed, in other words that this is possibly true, but so is the hot spot theory?

----sorry to be so tardy with the thanks, but I have been busy with my own project.

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