"Mountain building is not obvious.. "

 Certainly isn't .. (Hi Andrew).  [*Link death noted 20170919*.]  . 
( .. But what keeps making the Earth flatter (and smoother) than it used to be, is .. )

---

"Building"? .... What is it about mountains that gets 'built'? If mountains are really eroded plateaus (link.) and volcanoes, why does the term ["mountain building"] pervade the literature so to describe these landforms?   [56,200 - 20170919]

Fig.  1.  Drakensberg Mountains, South Africa.   A classic example of the way in which rock layers of one sort and another are piled one on top of the other to build mountains. No? That's not how mountains are built? ..

(More? .. )  =>

house  malt  rat  cat  dog  cow  maiden  man  judge  rooster  farmer  hhh

View from Alice's Tardis

(20170706-24) :-

Gravity, and the relentless imperative of flatness.

AGNEW, WESTERN AUSTRALIA

Western Australia's experience of The Great Regression = the time when the inland seas and lakes ran of the land into the developing ocean basins leaving in their wake - The Agnew Pub, .. which according to legend has been there forever.

C&P to Google Earth search bar < -27.952608°, 120.393448° >















(Agnew, Western Australia) [Picture = Agnew pub.]


Compared are two erosional surfaces that developed over Archaean granites. Note the very pronounced incision that can result from very slight topographical differences.   One surface is flat-as-a-tack, and only slightly lateritic (duricrust; darker brown in the upper central part of the figure) developed as a veneer on eroded, partly intrusive granite that formed a basement to inselbergs of tightly folded 'greenstones' [marginally submarine lavas, chert, iron formation and shaly and arenaceous sediments.] which form low hills out of the frame.

 The other surface is the more recent drainage cutting into the underlying lighter-coloured saprolite. The land drops about thirty metres over the step of the breakaway and a further thirty metres in seven kilometres towards the lower boundary of the figure .  The Yellow Pin marks some highly degraded sand dunes of indeterminate age on the older surface (possibly even partly older than the younger drainage radiating off the high ground?).The breakaway offers a good profile through the saprolite.

Not quite sure though what to make of the topographical contrast as regards climate variability.  Laterite forms in tropical and subtropical climates implying high rainfall.  Very selective chemical weathering is reflected by stony and spongy laterites being almost exclusively developed only over the more iron-magnesium rich greenstones which in the general area rise little more than fifty metres over the granite plain and are virtually absent over the granite duricrust.  The flatness of this granite surface is remarkable and is distinctive in having virtually no drainage.

About 10-15m below this laterite surface and slightly out of the frame is another, characterised by very broad open drainage (Link).  Two lateritic surfaces therefore.  Three, if that over the greenstones is counted, and all of them being cannibalised by the younger erosion of the present active profile.

Both surfaces (counting the two laterite surfaces as one) reflect a climate that was much wetter than today.  Despite today's rains being quite heavy on occasion and very quickly forming a sheet of water over the flatter parts of the landscape when it does rain, I personally doubt whether they could have caused the erosion apparent, which would appear to me to be much more likely due to the waning phases of that sub-tropical climate represented by the laterite  - when Australia (and Antarctica) (and Africa) were located much further north (closer to India)  [An old landscape indeed.]

 By its continent-wide distribution and extreme flatness, the lateritic duricrust is a surface of virtually zero erosion potential, .. as close to 'beach' and sea-level as it almost possible to be.  Not the sea of today however, but the anastomosing epicontinental 'seas' and lakes that covered the land before the breakthrough of the mantle of the Southern Ocean, remnants of which remain in the southward-draining, ennervated lake /river system of today.  The lighter-coloured, more recent aggressive fluvial incisison represents further reduction in response to epeirogenic (continent-wide) 'uplift' of the land outwards from the core [drop in sea-level].


(The Agnew pub?   Just a blast from the past, ... Visit it before any planned vacation to Mars.

One for the Hillbuildies

 .. The footsoldiers of Plate Tectonics ..
( .. "..snoring away like Rip Van Winkel" .. )

---

Even if midplate earthquakes are far less frequent than those on plate boundaries, if they have continued for any length of time they should have shoved up some hills."   (Shawna Vogel, p.165, "Naked Earth - The New Geophysics, 1996.

"Uhh?  ... Should have shoved up some hills.." ???

Well, ..why not?  Stands to reason, ...doesn't it?  Mountains can't just suddenly 'appear', .. ready-built, as it were, can they? They have to get pushed up by colliding plates, ...moving across the surface of the planet at the rate of centimetres a year.

That at least is the litany handed down by the Church of Plate Tectonics:  "Plates collide, crumple the crust and push up mountains."   So it's logical that before there are mountains there must be hills first.  (You have to laugh, ..little hills, .. sprouting like cabbages all over the place, ...getting pushed up and growing into mountains. If erosion doesn't get them first that is, and rub them all back down flat again.  In which case they would never get to be mountains. )

But (according to Plate Tectonics) they *do* get to be mountains.  Big ones, ..  Like the Himalayas.   The problem for Plate Tectonics however is that nowhere on the planet can anyone point to hills that are growing into mountains.


Read more ..

Truckies

(20170517)

Looking at things differently.

After a life of working (on and off) (mostly off) in the Australian bush I have an uneasy relationship with that particular example of natural environment.  The things that impress me most are the same things that (according to their diaries) impressed the early settlers who arrived on the beach in Western Australia in the early 1800's, culturally compromised by their pianos and the legacy of the mother country.  (Must've been tough.)  Those things are (and you can flick them on the fingers of one hand) :-  heat /flies/ dust /monotony and isolation.  Set them against the enervating monotony of the bush (arguably more grey than green), unrelenting blueness (sky&sun) and the fiery redness of the Earth and you get the picture of the heartland of Australia.  Nice, isn't it? (framed by the computer screen).  And it is too,  in winter.  Try it in 40-50 degree heat in the summer in 360 degree reality whichever way you look, while trying to catch a breath between every one of them.  (Any softness in it derives from relief from that experience of summer when it fries you!  Till you get used to it an any rate, and are thus prepared for the '"She'll be right, mate" signature statement of the Ozzie Cockie - the gate, (Bruce, I'll be bound)  [and the cocky ozzie with the ozzie cozzy) ("don't you wish your beaches looked a lot like mine"] .. held together by so many bit of wire it's like there's  more tumblers in it than the locks on the Bank of England.  Combine the heat, the gates and the language to go with both and you have the signature statement of white Australia colonisation.  (Why do I get this picture of the one-legged noble savage standing by, spear in hand, asking what we are doing?)

I can honestly say that any natural softness there is in it, of itself, lies (in my limited experience), in its indigenous people.  I find it odd, therefore, as to their choice of the sun (as "giver of life") as the centrepiece of their flag when surely water would would be more appropriate.   [I do struggle a bit with the sun (in the summer), giver of life or not.]

Flag.  As for the black (for the aboriginal nation)?   Something then about resilience and pride I guess.  But you know what they say about pride, so maybe we can settle for just some, and call it self-respect, but it's edgy, .. edgy.  Sounds to me the dominoes are a little bit round the wrong way in many things, particularly when one overshadows the other and refuses to budge.  Anyway, sun and water, .. we can split it, sun above, water below.  Or maybe left and right doesn't matter, .. surely both have to be in there somewhere as partners in this small matter of 'life' and its meaning in this big brown land - when it comes to nourishing little brown black grey green blue and white 'seeds'.] 


 Yet there *is* beauty in that harshness.  You see it more as you get older.  One I find is when you happen to be driving into the sun just after it has set.  Slivers of cloud just above the horizon divide the sky, .. 'sea' below, sky above, .. while further below the land darkens against encroaching night.  With a flip of the mind the road ahead changes.  The horizon shifts up into the sky, still ablaze in the wake of the sun to the fingers of cloud enclosing a tropical blue lagoon and a harbour of sorts.  You can almost see boats moored, .. or at least easily imagine them, while between the promontories of cloud lies the open sea, .. above the harbour the pink and gold of smaller clouds tinged with grey.

Now the road bends, taking you down to the sea.  The encroaching night and the heat of the day is behind you.  In front lies this glowing sheltered harbour of no ships,  no cranes,  no piles of containers, no gasworks, and no docklands of dystopian denizens. It's a rural fishing village, Mediterranean probably, an ideal in the mind's rosy glow of a simpler time. 

Funny how the mind switches like that to look at thinks differently.  It lasts for about fifteen /twenty minutes before you have to snap out of it and remember that the reality is still hundreds of miles away and night is falling, and you had better switch on lights and pay attention, .. but for a few minutes there is a window to a different reality. 

Truck drivers will know exactly what I mean. Maybe even wonder what it was was that pushed the aborigines away from that welcoming sunset coast and made them wandering souls in the crispy conurbations of bushy vicissitudes.  And the Innuit people of northern climes, pushed likewise into the icy wilderness where Frankenstein and the monster he created perished, abandoned and homeless on the altar of a "young girl's hideous imagination" that every year peeves schoolchildren who have to do it (so they do English rite).   Or for that matter the Wandering Tribes of Israel in the Arabian desert, whose bloodthirsty genocidal family history became the touchstone of  the civilised western world - a bounty that spawned the diasporean Scottish deal-maker, Donald-the-Trump who has invoked those ill-fated perambulations of Middle-Eastern folk (religious? - or just tribal) as a means of exorcising his curse of compulsive electioneering, but alas appears to have been scotched in his plan by the unravelling of his not-so secret dealings with that other card in the pack, Vlad-the-Putin, .. known for the boot when he's not impaling his political foes on poisonous chemicals of one sort or another (Link added) - and pallying up to birds of feathers similar to himself. 

All of which is to say that 'truckies' and different ways of looking at things (or not), the more things change, the more they stay they same.  'Twas ever thus.