Part 50- The Blocky Rectangle Slide at Seth

Copyright ESA/Rosetta/MPS for OSIRIS Team MPS/UPD/LAM/IAA/SSO/INTA/UPM/DASP/IDA/A.COOPER

Key:

This is a narrative key with some sections divided into paragraphs. The key ends at the next sub-heading. 

Red arrows- slide directions. The two longer arrows correspond to the same slide. The upper of the two is aligned along the centre of the top surface of the blocky rectangle and depicts its direction of slide i.e. along the same direction as its long axis. The lower of the two is the slide track of the base of the rectangle which is of course in line and in the same direction as its partner arrow on the top surface of the rectangle. The top arrow therefore used to sit directly above the bottom arrow. Both arrows are about 200 metres long perhaps a tad less. The short arrow depicts the sliding of a smaller lump at 90° to the blocky rectangle slide. This is in keeping with the 1.6 km x 200m rift described in Part 49. That rift was described as opening up at 90° to the long fault along which the blocky rectangle slid. 

Bright green- the upper line runs along the top of the blocky rectangle. You can see the other side of the rectangle too but just for clarity to pick it out from the background: it’s an almost mirror image line to the green one (including the central dip) on the other side of the arrow running down the centre. So the arrow is the line of symmetry. The lower bright green line runs along the rim of the very straight, shallow trench that the blocky rectangle once sat in. Since the rectangle slid backwards along the arrow direction, it therefore slid along the trench, hugging the rim as it went. The lower bright green line therefore matches to the base of the rectangle’s cliff, which is in very dark shadow. The cliff base used to sit along this lower line. The cliff of the blocky rectangle itself carries on a little further into the shallow trench and was always hidden behind the trench rim, even as it slid. 

Pale orange- this is the boulder field that relates to the blocky rectangle’s rugged cliff face that’s in complete shadow. The boulder field stops abruptly halfway along the cliff and is therefore staggered from the current position of the cliff face it fell from. This is because the boulders fell away from the cliff when its base was still seated along the lower bright green line. 

There’s an abrupt line between boulders and dust at the far end of the boulder field. This sharp demarcation line is at 90° to the cliff face and alongside the position at which the far end of the cliff used to sit. Since the boulder field is the same length as the cliff, and staggered, it’s clear that the cliff used to sit along the lower bright green line. Ergo the blocky rectangle has to have slid along the direction of the arrows from the seating to its current position. 

The boulder field was almost certainly produced as a result of the 1.6 km x 200m rift in Part 49 yanking the boulders out of the cliff as material tore away at 90° to the cliff. This means we can be sure that the rift happened first and the blocky rectangle happened second and probably as a result of being free to follow its preferred tensile stress vector, along the paleo equator. Please see Part 49 for these differential tensile stress vectors either side of the rift that caused it to open in the first place. 

Mauve- the mauve line in the foreground is part of the ‘mauve anchor’ (Part 24), one of four resilient massifs from which both the head lobe and the red triangle recoil tore away. The mauve line in the background runs along the clifftop of the front face of the blocky rectangle. It then carries on for a short distance. 

The front face the rectangle clamped to the back of the mauve anchor, behind and below the mauve line in the foreground i.e. hidden from our view from this perspective. The head lobe was clamped to the near side of the mauve anchor. This is why the mauve line in the foreground is so ragged: it had material tearing both from behind it and in front of it. The section of the mauve line across the front of the blocky rectangle fits well to the right side of the mauve line in the foreground. The extension to the left doesn’t match for two reasons. Firstly, it was attached to material on Serqet (the head lobe rim component of the mauve anchor). The two sections kissed either side of the ragged foreground line which is now a vestige from inside that violent tear. That’s why it’s ragged and tapers down while the mauve rectangle extension stays high (as does the head rim match). Secondly, the material next to the front cliff of the blocky rectangle recoiled back somewhat like a blanket. That’s not a fudge- there’s plenty of evidence for it, some published, some yet to come. 

Red- this is a nice piece of evidence for the 1.6 km x 200-metre rift in Part 49. The lump on the right was attached to the recess on the left. This match holds up very well in other views too. The small dots denote the far rim of the lump that’s out of view as well as its seating which is in view. So all larger red dots are in view. This lump has a slide vector as denoted by the arrow. You can see that the arrow is at 90° to the blocky rectangle slide. This is because the line along which the rectangle slid (the bright green rim of the trench) is a very straight line and a weak point brought about by the tensile forces of stretch. This line stretches 1.6 km into the distance (off-frame to top-right) and was the cause of the 200-metre-wide rift, to the right in this view. Hence, the little red lump moved to the right. The slide distance of the lump as well as the width of the pale orange boulder field are about 100 metres which is half the width of the 200-metre rift. The opposite perimeter is off-frame to the right. 

Orange- this is what appears to be a nice mini match. It’s the only new discovery in this post. It’s not quite definitive and needs more close-ups from different angles to verify it. In the meantime, it’s up to the readers to ascertain for themselves how likely it is by checking the unannotated version. Of course, if it holds up, it has important implications. The short crack along the far line has been cited in the morphology papers as being a section of cliff that’s cracked because of erosion and on the point of collapse. However, if it did sit on the suggested seating, it simply means that it was wrenched from that position as a ready-made overhang and cracked for that reason. This means that no erosion is necessarily at play in the formation of this overhang. Incidentally no erosion is necessarily at play in any of the rugged cliffs, boulder fields and outcrops in this roughly 500m x 800m view. In fact, stretch theory has already shown that every one of the cliff features in this view has either torn or slid and all boulder fields (including those in the ‘slide trench’) have come about as a result of tears and slides. Athough erosion via sublimation must be happening it’s probably responsible for a fraction of one per cent of what we see in this photo. Hence the need for the obligatory inclusion of the word “necessarily”, above. 

PREVIOUS REFERENCES TO THE BLOCKY RECTANGLE SLIDE

The blocky rectangle slide isn’t a new discovery. It was first published in Part 26, a year ago (see sub-heading ‘signature 6’ in that Part). That sub-heading has a photo showing what is called the ‘red triangle recoil’ which was a 200-metre recoil of the top crust, away from the shear line where the head lobe rim sheared from. 

The direction of the red triangle slide was exactly along the direction of the paleo equator that defines the paleo rotation plane. The paleo equator is quite close to the current equator. So the red recoil slide, including the blocky rectangle in this post, Part 50, slid along the paleo rotation plane. 

Since the tensile force vector induced by spin-up of the comet would act along the paleo rotation plane, in a direction towards the stretching long-axis tip, it means the entire 1-kilometre-wide slide succumbed to that same tensile force vector. This blocky rectangle is just the end section of the red triangle recoil. 

There’s a wealth of additional corroborating matches along the line of the red triangle recoil that extends for a kilometre, all the way from the view in the header photo to Anubis (off-frame, a long way to the left). 

So the evidence presented here is now one year old and the slid blocky rectangle has been referred to on numerous occasions since as a key component in directing us towards other discoveries. These include what is now an intimate understanding of the morphology of the Serqet-Ma’at border. That border used to be clamped against the mauve line in the foreground and therefore to the blocky rectangle when it was seated. This is why the mauve line is so ragged. It had material tearing away from it on both sides. 

The sliding of the blocky rectangle was also key to noticing the 1.6 km x 200-metre rift in Part 49, published recently. 

All the information on the blocky rectangle slide given here was also given in a comment I made on the Rosetta blog some while ago. It was in response to a blog post that contained a very similar close up view of the blocky rectangle, taken from an OSIRIS paper. I made the comment describing the sliding process, the trench and the staggered boulder field in order to show that vast chunks had slid hundreds of metres and that this was evidence for stretch theory. So this part is a second attempt to persuade the Rosetta mission scientists that the blocky rectangle slid 200 metres. This time with a more detailed photo, the argument holds up and is still more compelling with the added red lump slide and the proposed orange crack match.  

TWO BLOCKY RECTANGLES

Regular readers will know of another ‘blocky rectangle’ part of the red slide on Imhotep. Apologies for the duplication- I forgot about this one when I tentatively named the Imhotep one. This one takes precedence because it was first coined long before the Imhotep one and it’s also more rectangular and blocky. So we’ll have to find another name for the one on Imhotep. 

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