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Posted on 11/28/2006 8:15:18 AM PST by cogitator
A mixed bag this week. Leading off with a view of the lava pond in Pu'u O'o, churning away:
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Number two; it's Mars geology, new images from the ultra high-resolution HiRise camera on the new Mars orbiter. Web site: HiRise Transition Phase Imaging (watch out for big image sizes if you want to download any)
This is full-resolution; the smallest features are 5 cm. This image is entitled "Terra Sirenum Gullied Crater". 
And finally, the world's largest pothole (hole in bedrock formed by rock gouging in a glacial stream). I didn't know there was a winner in this category, but that's what the sign says. It's the Archbald Pothole in Pennsylvania.
Ping: I should have mentioned that you can click the first picture for a twice-the-size full-size version.
Hmmmmmn.
Pothole seems a poor term: more related to holes in a formed surface like a road.
So, since a sinkhole is formed differently than a "rockhole" (if the rockhole is formed by erosion of solid rock by falling water, and a sinkhole is made by loose water-soaked soil falling down), then what would they term the world's largest sinkhole?
Couldn't also be a pothole I would say.
The more standard sinkhole definition is a hole formed by surface collapse into a subsurface void caused by subsurface erosion. Most commonly referred to in karst terrain, where the erosion is chemical, but can also happen mechanically.
So Florida's typical problems then would be physical (flowing underground water), rather than the chemically-caused limestone holes in, say, central Yucatan, right?
Central Florida is a karst region, too, so the subsurface erosion is (probably) primarily chemical, with a bit of mechanical weathering due to current flow.
Thanks for the ping! I like that picture of the volcano. :o)
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