Discussion Topic |
|
This thread has been locked |
MH2
Boulder climber
Andy Cairns
|
|
|
Topic Author's Original Post - Feb 27, 2018 - 07:02pm PT
|
The rock is conglomerate. That is an introductory enigma.
How do so many water-rounded rocks get piled up together?
A reasonable explanation can be found by looking at what Wikipedia has to say about Meteora, in Greece.
As I understand it, deposition is a slow process. Somewhere I learned that sediment at the bottom of oceans accumulates at a rate of about one centimeter per century. Over geologic time, that can add up to a lot.
However, where rivers run in to the ocean, material transported by the river may accumulate at a faster rate.
In Ontario I was fascinated by the limestone cliffs of the Niagara Escarpment. The little fossils at the base of the cliff could be millions of years older than the little fossils at the top, if my one centimeter per hundred years is anything close to right.
However, in a conglomerate of large pebbles like Meteora or Maxwell, the rocks at the bottom may be almost the same age as the rocks at the top, in geologic time.
bottom
top
I will let you know when I find a dinosaur egg. Pretty sure I spotted a mummified hatchling.
|
|
Reilly
Mountain climber
The Other Monrovia- CA
|
|
|
Feb 27, 2018 - 10:08pm PT
|
That looks a lot like much of the Olympic Mts - olympian in their chossitude although,
to be more accurate, I guess ‘pillow lava’ is a different clause in the Faustian bargain.
|
|
MH2
Boulder climber
Andy Cairns
|
|
|
Topic Author's Reply - Feb 28, 2018 - 08:15am PT
|
Other mysteries, to me:
Why the big holes?
Why are some lined up while others are not?
So far, the bolts I have hung from and the holds I have pulled on have been secure. The base of the main cliff has large sections that look ready to peel away, and down below there are quite large boulders. Pretty far down below.
|
|
Reilly
Mountain climber
The Other Monrovia- CA
|
|
|
Feb 28, 2018 - 08:19am PT
|
So far, the bolts I have hung from and the holds I have pulled on have been secure.
Obviously! 🤡
|
|
MH2
Boulder climber
Andy Cairns
|
|
|
Topic Author's Reply - Feb 28, 2018 - 08:25am PT
|
You sure those bolts arn't just punched into a coupl'a ol' igneous rox and will pop out when body weight is taken?
A little to one side of those bolts:
Much of the area is untrammelled. Very little sign of climbers. A lot of sign of deer. In looking around I often reassure myself by thinking that if deer came up this way, I can probably get down it.
|
|
MH2
Boulder climber
Andy Cairns
|
|
|
Topic Author's Reply - Feb 28, 2018 - 08:29am PT
|
Reilly, not completely obvious.
I rap down and auto-belay up. I usually back up anchors with a rope tied to a tree. I don't know who placed the bolts, and the guide does say that there is loose stuff.
|
|
Reilly
Mountain climber
The Other Monrovia- CA
|
|
|
Feb 28, 2018 - 08:33am PT
|
not completely obvious.
True, I was going to add that perhaps you were posting from hospital,
but I don’t think of you as a troll.
|
|
Mighty Hiker
climber
Outside the Asylum
|
|
|
Feb 28, 2018 - 09:43am PT
|
Andy, while you're there, perhaps you could visit Eric's grave. At the Anglican church (Saint Mary's) on SSI.
|
|
MH2
Boulder climber
Andy Cairns
|
|
|
Topic Author's Reply - Feb 28, 2018 - 11:23am PT
|
Yes, Anders.
I only recently was told and will visit next time we are over there.
We currently spend 2 weeks in W Van and then 2 on SSI
|
|
MH2
Boulder climber
Andy Cairns
|
|
|
Topic Author's Reply - Feb 28, 2018 - 11:25am PT
|
Hey, thanks for the info, Dingus!
I am grateful for the word 'cobbles' which is what I was needing.
|
|
mike m
Trad climber
black hills
|
|
|
Feb 28, 2018 - 12:44pm PT
|
|
|
clode
Trad climber
portland, or
|
|
|
Feb 28, 2018 - 02:20pm PT
|
In geologic terms, conglomerate is a sedimentary rock, comprised of sediments ranging in size from small clay-sized particles, to boulders, feet across, with the predominant grain size typically in the relatively large (i.e., cobbles to boulders) size.
Think of loose, gravel pit material, held together with some form of "glue". The key to whether this rock type is chossy or climbable, lies in the "glue". The Troutdale Formation, near Portland Oregon, is an indurated, or "glued" gravel, in which small, clay particles, mixed in with the larger particles, holds the material together. The bond between the clay and larger gravel particles is strong enough for the formation to maintain vertical cliffs or outcrops, but weak enough so that trying to climb on it will rip and tear it apart (i.e., you'll fall).
By contrast, the rock in the New York Gunks, is a conglomerate where the particle sizes are more pebble size, than boulder size. The reason it is great for climbing is that the "glue" is quartz, which has a relatively much stronger bonding power than clay.
(Your friendly neighborhood geologist. My Master's Thesis was on the Troutdale Formation, and I've climbed in the Gunks and seen the rock up close and personal).
|
|
Clint Cummins
Trad climber
SF Bay area, CA
|
|
|
Feb 28, 2018 - 02:45pm PT
|
BJ's linked geologic map
http://www.empr.gov.bc.ca/Mining/Geoscience/PublicationsCatalogue/OpenFiles/2009/Documents/2009-11/OF2009-11.pdf
shows several formations on Mt. Maxwell.
KB at the summit (Baynes Peak)
DN to the northwest
Dg contact to the southwest
However, the close up photos of the rock look similar to what we have at the Pinnacles National Park, which I have heard called breccia or tuff -
a bunch of volcanic clast stones in a matrix of ash. So the layer
DMg/DMt may also be present (it's on the mountain to the south).
But DN and DMg/DMt may look similar to a climber....
|
|
Oplopanax
Mountain climber
The Deep Woods
|
|
It's definitely not breccia or tuff. It's a thick layer of sedimentary conglomerate. The bed runs all the way from the Chuckanut Mts near Bellingham thru the San Juans and up to near Nanaino... interrupted by a couple of folds. Several generations of UBC geologists have mapped it at field school.
|
|
Jeff Thomson
Sport climber
BC
|
|
I really enjoyed reading this thread. Saltspring Island is my only experience climbing on this kind of rock. I really enjoyed it in a perverse sort of way. Seriously though the 2 pitch 10 - something on the main wall was one of my all time favourites. Maybe it was the location, which was beautiful, or that it was my 20th anniversary get away (yes thats where we went), but either way, I thought it was great and I'd go back in a heart beat.
|
|
kpinwalla2
Social climber
WA
|
|
The holes are tafoni - google it. The holes line up because of the consistency of the weathering properties of individual layers in the sandstone/conglomerate. It's thought that salt crystallization plays an important role in the weathering that creates tafoni.
|
|
MH2
Boulder climber
Andy Cairns
|
|
|
Topic Author's Reply - Mar 1, 2018 - 06:52pm PT
|
All interesting.
From BJ's link above:
The Extension Formation has been interpreted to include high-energy deposition in deeper marine submarine canyon and fan facies in northern areas of Nanaimo Group, and shallow marine to coastal to braided fluvial depositional environments in the Nanaimo area where coal is present. This rather wide range of depositional environments seems a bit odd as a single formation, but my grasp of the Nanaimo Formations is limited.
I notice that geologists often sound tentative, an admirable tone to use for events that happened so long ago, often involving forces far outside our direct experience. Does high-energy deposition mean a submarine slide?
The KB which BJ earlier directed me to is the Benson or Comox formation. It is the deepest named layer of the Nanaimo Group. Whether the conglomerate of the Comox Formation was deposited in a marine environment or not is unsettled, I think:
The Nanaimo Group begins arbitrarily about 90 million years ago and ends abruptly with the strike of the large meteor or comet 65 million years ago.
When I divide the 4 km thickness of the Nanaimo group by the 25 million years it represents, I get a deposition rate of 1.6 cm per century.
edit:
source of the images above
https://www.uvic.ca/science/seos/assets/docs/PenderFT13.pdf
I wonder if the large holes in the cliffs could be places where gas pockets formed.
My own history with Maxwell goes back at least to 1994 when our kids went to a summer camp below it.
How Maxwell looked in 1994
We may have visited when we were living in Seattle between 1979 and '87.
Seattle climber Jon Nelson lived on Salt Spring for 2 or 3 years and climbed on Maxwell.
|
|
Mighty Hiker
climber
Outside the Asylum
|
|
If one hand-drilled a bolt there, would it be necessary to use Maxwell's silver hammer?
People hang-glide from those cliffs, or somewhere on the island anyway.
|
|
kpinwalla2
Social climber
WA
|
|
The large holes are NOT gas pockets, they're produced by subaerial weathering.
|
|
MH2
Boulder climber
Andy Cairns
|
|
|
Topic Author's Reply - Mar 1, 2018 - 07:15pm PT
|
People hang-glide from those cliffs, or somewhere on the island anyway.
I can check the Maxwell final plan for you:
Rock-climbing is No No No whereas as bouldering is No No Yes, meaning that bouldering will be allowed in specially designated areas. I am not sure whether this plan ever got out of the planning stage.
Thanks, kpinwalla2. I hadn't seen your first post when I was composing the long one below it. I have now looked at a few of the links as to how such pockets form.
|
|
|
SuperTopo on the Web
|
Let us know!