#Fold mountains
8 messages in this thread
Hi, Kamron–
As noted in another message, I blooped in speaking of a root as deep as the
mountain is high – I should have multiplied root depths by 5 or 10, since the
air/rock density ration is much greater than crust/mantle density.
The Scientific American of Oct 1993 article on large igneous provinces shows
the Broken Ridge plateau and the 90-East ridge as being such. It implies the
Kerguelen plateau and the Broken Ridge plateau formed from a single mantle
plume. I take this to mean the plume formed a hot spot and erupted at the
southeast Indian spreading ridge, forming something like Iceland, which was
later split by the ridge. Perhaps the hotspot actually arrived quietly, built
the 90-East ridge over time, then got hotter and produced the plateaus? This
would be the reverse of normal hotspot arrival protocol.
I also recall reading elsewhere that Kerguelen includes some continental
material; perhaps a New Zealand-like fragment happened to be near the line of
fire.
–Doug
Doug
>>The Scientific American of Oct 1993 article on large igneous provinces shows
the Broken Ridge plateau and the 90-East ridge as being such. It implies the
Kerguelen plateau and the Broken Ridge plateau formed from a single mantle
plume. I take this to mean the plume formed a hot spot and erupted at the
southeast Indian spreading ridge<<
I agree that they were mated at one time..it follows that they are equal
distance from the Mid Ridge.
>>Forming something like Iceland, which was later split by the ridge. Perhaps
the hotspot actually arrived quietly, built the 90-East ridge over time, then
got hotter and produced the plateaus? This would be the reverse of normal
hotspot arrival protocol.<< The key here is the geological table included in
the formation. If it has the layers of time then it was crust regardless of
what happened in the course of time.
>>I also recall reading elsewhere that Kerguelen includes some continental
material; perhaps a New Zealand-like fragment happened to be near the line of
fire. <<
It definitely appears to be a crustal section. I actually expect geological
table in all plateau's of any size. Ha there been any drilling and cores taken
in the Hawaiian Islands?
Kamron
Hi, Kamron–
>> The key here is the geological table included in the formation. If it has
the layers of time then it was crust regardless of what happened in the course
of time.
As I said, there was one other article that remarked there was some continental
material there, and some maps showing a small fragment from
Antarctica/Australia that was running around loose for a while near the ridge
then disappeared from the maps. It may have been a stray continental lump that
got plastered with megatons of basalt from being in the wrong place at the
wrong time. Or maybe the continental nature was an assumption invalidated by
the seismic and sampling indications mentioned in the large igneous provinces
article.
>> Has there been any drilling and cores taken in the Hawaiian Islands?
Probably, but I do not know of them. Wake me up when Mauna Loa spits out a
piece of continental crust… I gather volcanic eruptions are liable to bring
up occasional stray chunks of deep rock.
–Doug
Doug,
>> >> Has there been any drilling and cores taken in the Hawaiian Islands?
>> Probably, but I do not know of them. Wake me up when Mauna Loa spits out a
piece of continental crust… I gather volcanic eruptions are liable to bring
up occasional stray chunks of deep rock. <<
Must have been — I know the entire Hawaiian chain of seamounts has been dated
by radiometric methods. That must have required coring in the sunken seamounts
northwest of Midway Atoll.
Also, I don't think it's likely Mauna Loa or Kilauea will be 'spitting out'
continental crust anytime soon. The Hawaiian volcanoes are noteworthy for
having some of the most fluid, least explosive lava to be found anywhere on
Earth. Even mildly explosive eruptions are almost unknown on Hawaii, and as
for violent blasts like Mt. St. Helens or Tamboro, forget it.
JSW
>> >> Has there been any drilling and cores taken in the Hawaiian Islands?
>> Probably, but I do not know of them. Wake me up when Mauna Loa spits out a
piece of continental crust… I gather volcanic eruptions are liable to bring
up occasional stray chunks of deep rock. <<
Must have been — I know the entire Hawaiian chain of seamounts has been dated
by radiometric methods.<<<
Read a book on Hawaiian Geology once. Entirely volcanic except for a few
uplifted recent reef limestones. Volcanic rock is exposed on all 8 of the main
islands and up the chain at Gardner Pinnacles (?) and French Frigate Shoal (?).
I believe they sunk cores at Midway. As I recall there was one small odd patch
of volcanic rock somewhere in the chain that didn't fit with the rest of the
Geology, but I don't recall the details.
Hi, Jon–
I would be a bit stirred up if Mauna Loa 'spit' rocks forcefully or a lot
stirred up if it brought up continental rock. I have heard mention of
volcanoes bringing up presumed mantle rock fragments, but do not recall what
type of volcano that was. I have a fuzzy notion it was some sort other than
the really fast, forceful eruption that I gather produces kimberlite with
diamonds, but was it ordinarily-explosive eruptions (whatever I mean by that)
or peaceful ones like Mauna Loa favors?
–Doug
Doug
It would be great to have access to a database of core samples from around the
world. Is there anything like this anywhere?
>> As I said, there was one other article that remarked there was some
continental material there<<
Do you have a reference to that article?
Kamron
Hi, Kamron–
I am packing for my imminent move back to Calif., thus my Scientific Americans
are no longer arranged for a quick search of favorite articles. If my memory
gets jogged about what else was in the same article, I may suddenly zero in on
it; if not, remember to jog my memory when I am settled again in April.
I wish I had electronic copies; then a simple search for the word Kerguelen
would turn it up fast.
–Doug