Dear colleagues
I am stydying two circular ponds with a ring (see attached photos). I cannot figure out if they are impact craters or maars. Could anyone help?
Best regards
Ioannis
Based on the photograph, these appear to be circular, with symmetric mounds on the margins. They are unlikely to be due to meteorite impact, which come in at a relatively low angle to the surface, and which cause an assymetric debris field. Describe the nature of the mounds where exposed; if hydrothermal or small diatreme, they will have characteristic bedded features due to eruption (vs impact). See Hedenquist and Henley, 1985, Economic Geology, for a description of hydrothermal eruption mounds (access via ResearchGate); diatreme deposits are described elsewhere in the literature (e.g., Davies et al., 2008, EG).
THANK YOU FOR YOUR INTERESTING ANSWER AND THE REFERENCES JEFFREY.
BEST REGARDS
IOANNIS
Please examine the geology around the crater. If these craters are volcanic then there should be volcanic rocks around the craters. But looking at the pics, it does not look like a volcanic crater... Another feature like looking around the craters, it seems like small pits. So I believe these are impact craters.
There is raised rim around half of the depression (including where the 3 cars are parked) and that is indicative of an impact crater.
In my area a major road goes over the edge of a 220 m.y.old, 40 km-wide impact crater and a pronounced "bump" (where the rim was) still exists along that road.
Such the rim could be formed when regolithSuch the rim could be formed when regolith are squeezed out by ice expansion when water freezes under permafrost conditions.
...same way...
Only from the photo one can assume the residual form after the mud volcano. are squeezed out by ice expansion when water freezes under permofrost conditions.
DEAR RANJIT, MICHAEL AND NADINE THANK YOU FOR YOUR INTERESTING VIEWS.
BEST REGARDS
IOANNIS
why not a sink-hole?
It depends on the lithology of the country rocks.
Fundamental information is missing.
michele
DEAR MICHELE
GOOD MORNING AND THANK YOU FOR YOUR ANSWER. THE PONDS ARE NOT SINK-HOLES (ESPECIALLY THE LARGER ONE) SINCE THERE IS A RING. THEY ARE EITHER IMPACT CRATERS OR MAARS. REGARDING MORE DATA, I HAVEN'T BEEN IN THE FIELD YET BECAUSE THE AREA IS AT A 1570M HIGH PLATEAU AND IT IS COVERED BY SNOW NOW.
BEST REGARDS
IOANNIS
Dear Ioannis,
what is geology around? volcanics?If geographically correct, I believe your circular structures seem to be Permafrost topography, rather than impact or eruptive crater. Good luck
Erkan
DEAR ERKAN
GOOD EVENING AND THANK YOU FOR YOUR ANSWER. I HAVEN'T BEEN IN THE FIELD YET. THE AREA IS MAINLY LIMESTONE. ALSO, FROM AERIAL PHOTOS I SAW SOME DARK ROCK EXPOSURES. THEY LOOK LIKE VOLCANICS. I DON'T THINK IT IS PERMAFROST BECAUSE THE RING IN THE LARGER POND IS COMPLETELY CIRCULAR.
BEST REGARDS
IOANNIS
I propose you to check especially southern Chilie, Argentin (Patagonşa) and British colombşa. You will find perfect circular structures together with other forms. they are to small to be maar, honestly (about 40-45 meter in diameter, scale:car length)
DEAR ERKAN
THERE IS NO PERMAFROST IN THIS PLATEAU (1570M). ALPINE TUNDRA APPEARS AT AN ALTITUDE OF >1800M IN THIS AREA. REGARDING ITS SIZE, IT IS AROUND 60M ACROSS (GOOGLE MAPS). NOTE THAT SMALL DIATREMES DO OCCUR (E.G. MERLIN PIPE IN AUSTRALIA).
BEST REGARDS
IOANNIS
The photos are not enough! A picture of a cross section of sediments forming the depression rims ( PLUS A PETROGRAPHIC ANALYSIS!!!!!!) could unequivocally indicate if the circular structure is linked to maar or to impact phenomena. PAX ET BONUM
DEAR FEDERICO
GOOD EVENING AND THANK YOU FOR YOUR ANSWER. I HAVEN'T BEEN IN THE FIELD YET DUE TO SNOW COVER (ALTITUDE OF THE PLATEAU 1570M). WHEN I GO THERE I WILL TAKE SAMPLES.
ΟΨΟΜΕΘΑ
IOANNIS
DEAR IOANNIS ,
AFTER CHECKING AND SAMPLING INFORM ME PLEASE ABOUT YOUR CONCLUSIONS, MOREOVER MAIL ME PLEASE SOME PICTURES.
SALUTI!
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