Some More Example Terrains
Over the past couple of days, I’ve started looking at the Planet Four: Terrains classifications data. I’ll be looking at how best to combine the assessments to identify the different terrains, but for now I’m taking a preliminary look at the raw data. I tallied up the votes for each of the images we’ve shown on the site that have been completed (have had at least 20 independent reviews). Perusing the results I have found some nice examples that I thought I’d share below.
Swiss Cheese Terrain
You can also find more examples on our Site Guide.
Nice to see those images of channel networks. I have been collecting a series of similar ones:-
484472,484477,484478, 484480, 484484,484485,
#484565, #484569, 484571, 484573, 484574, 484576, 484576
2 of yours are the ones with the #. I don’t have your middle one.
I started collecting these because, even though they are channels which, to my eyes certainly show up as negative features, they look so much like a dike swarm. If you look at the ones I’ve listed above you will see that all the channels are trending in the same direction, which is often the case in a dike swarm, but dikes are normally more resistant than country rocks and stand out as ridges although they can on occasions be softer. So this extensive channel network is certainly interesting.
I would really appreciate getting access to the missing subjects in the above list and, if possible, a composite of them all. There are 2 sequences and my guess is that they are adjactent to each other.
If these are interpreted as channels having formed by a similar mechanism to spiders I would be interested to hear of how you explain thier parrallelism , over what appears to be quite some distance.
Subject 484569, the last on your blog, is particularly interesting because the channe.s stop abruptly at what appears to be a cliff face. This also needs an explanation with respect to any genesis postulate.
Looking more closely at the cliff base in Subject 484569, it almost looks as though the channel network is unconformably overlain by a layered deposit in the cliff.
I must take back that comment about channel networks being unconformably overlain by layered deposit in cliff. LOOKS CAN BE DECEIVING!
Studying subject 484569 again this morning I notice a few more informative features which clarifies the geological interpretation and suggests the opposite of what I said in my last comment, namely:-
a. If you look at the little pedestal crater in the lower left quadrant you will notice a darker area, between it and the left margin. I see it as a shaded cliff of SPLD, devoid of channels.
b. On the other side of the image, the right, opposite the pedestal crater, there is a bend in the cliff.
c. Between these two, a. & b. , there is a trapezoidal area with a course network of comparatively deep channels.
d. The coarse channel network stops abruptly against the main cliff (that at the bottom of the image which shows some layering/banding and is suggestive of SPLD i.e.along the shorter, upper, side of the trapezoid) .
e. The long base of the trapezoid is a line extending to the right from the base of the left smaller cliff (a.). This line is defined by a sudden change from a coarse network of deep channels to a finer network of shallower channels.
I now, therefore, interpret this trapezoidal area as a CHANNEL-COVERED TALUS SLOPE below the main cliff of South Polar Layered Deposit material. This does away with any suggestion of channel networks being unconformably overlain by the layered material in the cliff. Sorry about that.
Also of interest:-
f. At the center-bottom of the image the cliff face turns suddenly towards the bottom of the image. There is another flat area with a finer network of channels between here and the smaller cliff which lies bewteen the pedestal crater and left margin. This land is lower then the plateau above the cliff but higher than the land beyond the talus. One could interpret this as 3 erosional landsurfaces; an upland, devoid of channels, above the main cliff, a midland with a fine channel network (on which the pedestal crater sit) and the channel-covered lowland beyond the talus. The small cliff between the pedestal crater and left margin separates this lowland from the midland. Alternatively, the offset cliffs and 3 different land levels could be the result of faulting of the South Polar Layered Deposit.
I would say the above also goes to suggest that the smooth channel-covered terrain is YOUNGER than the South Polar Layered Deposit and a suitable environment for channel formation only existed at an elevation up to that of the midland and not up to that of the highland.