Thats an interesting question, I'd thought the cracks extend down to the base and perhaps beyond whatever the boundary of the top cracked layer is. I dont expect the cracks are completely random and line up by chance, I'm assuming they are caused presumably by dessication shrinkage withing a large segment, so a crack could extend below and across the subsequent sequence of broken sub-blocks and layers hidden below the thin litter of soil that currently lies atop.
Along those lines, the crack line Bunker9603 is curious about would extend across several broken blocks as a large segment cracked into smaller blocks and its vertical layers detached from each other, some block layers perhaps subtley shifting as soil weathers away, allowing soil to attempt to fill the linear gap across the now separate sub-blocks and sand..

Take a tiny topographic feature.

Take prevailing winds.

Apply a couple of billion years.

You'll get patterns, lines, features, streaks and all sorts of things that look like they're interconnected.

Take a tiny topographic topic.

Take prevailing views.

Apply a couple of UMSF posts.

You'll get opinions, lines of thought, factions and all sorts of things that look like they're interconnected.

True, get enough monkeys typing and they recreate the Library of Congress, but isnt the Meridiani terrain basically formed of dessicated deposits? it seems to follow that you might have a lot of intersecting cracks form with certain ones becoming dominant as dessication progresses further, subbsequent wind erosion should reveal rather than create such features, finally leaving stuff like we see today.. i see similar patterns in dried-up river silt. But of course thats my lay interpretation, hopefully one of the Geologists reading here can set it straight.

It's been a long time, but back when Opportunity left Eagle crater there were some major cracks or maybe they should be called crevices. I can't remember the geological term used to describe them, but I believe they all had a similar, or at least a preferred, orientation.

Haven't seen anything like that since however. Can anyone remember if that common orientation was confirmed? Meridiani Planum might be experiencing common stresses, although personally I don't even see the claimed long crack in the surface rocks at our present location. I am only saying that if someone did demonstrate a common orientation of cracks it would not be all that surprising. However, I am not geologist, and I only chimed in on this subject because it reminded me of those major cracks or crevices near Eagle crater. And that we never saw any more.

No, there's no common orientation. It's just local phenomena everywhere, vaguely polygonal or rectilinear fracture patterns caused by dessication and shrinkage or localized shifting of layers due to impact, erosional unloading or changes in ground water. My point earlier was that you can explain general phenomena but it's a waste of time trying to account for every individual crack, just like it would be a waste of time trying to account for the shape of every individual rock on a beach.

Phil

Another significant drop in the local horizon tosol - not long now folks!

http://qt.exploratorium.edu/mars/opportuni...GFP2360L2M1.JPG
Compared to this just 80m back
http://qt.exploratorium.edu/mars/opportuni...00P2359R2M1.JPG

Things are happening fast now

I'm now guessing that we will pass to the south of Approach Crater in a more direct line to Cape York. There's a sharp little crater down there just inside the estimated visibility line, which might be on our route. Just 3 more driving sols to visibility of Cape York, by the standards of recent "long" drives", and perhaps 5-6 drives if they are of the shorter drive variety. Not forgetting that the MER mast height may give us earlier visibility than the line suggests...

Another great view

http://qt.exploratorium.edu/mars/opportuni...GFP2360L2M1.JPG

There is a tiny bump to the right of the "approach crater"

I do think however that Opportunity will make one more small dip downward based on how they are positioning her.

Almost certainly a little ripple beside AC. One of the "sore thumbs" we talked about.

About the route to come, it does look as though we're heading straight towards Spirit Point, but on the other hand we're now sitting very close to "Stu's Notch" (sorry, Stu!), so I could still see us heading to Approach Crater next. One more drive and we should know which it is.

I'd say I can see a little bit of the interior of Approach Crater now and the "unnamed crater" on the other side of Endeavour is now again fully visible.

To summarize the discussion of the past several pages in graphic form:

Full view of Cape York, per Stu:


Full view of Cape York, per Doug:


Did I get that right?

A picture (or a pair of pictures) is worth a thousand words!

Phil