Geology Question of the Week

  • 172 Replies
  • 169372 Views

0 Members and 1 Guest are viewing this topic.

*

Offline Bass

  • Neilep Level Member
  • ******
  • 1340
    • View Profile
Re: Geology Question of the Week
« Reply #50 on: 13/01/2006 05:08:05 »
Rocks can develop planar features for several reasons- the most common are bedding planes.  The next most common is pictured here- in the top photo, bedding is obvious and aligned with the blue pencil, the second planar feature cuts across the bedding and is aligned with the black pencil.  In the bottom photo, bedding is the crinkled colored layers while the second planar feature is almost vertical (aligned with knife):




GQOTW:  Name this planar feature?

Bonus:  How does this planar feature form?  What does it tell us about the history of the rock?


Subduction causes orogeny.
Old enough to have a grandson
Slow enough to study rocks
Thirsty enough to find a pub

*

Offline Bass

  • Neilep Level Member
  • ******
  • 1340
    • View Profile
Re: Geology Question of the Week
« Reply #51 on: 22/01/2006 01:46:06 »
Hint:

Wonderbra -
what most men first notice about a woman wearing a wonderbra.

Subduction causes orogeny.
Old enough to have a grandson
Slow enough to study rocks
Thirsty enough to find a pub

*

Offline Bass

  • Neilep Level Member
  • ******
  • 1340
    • View Profile
Re: Geology Question of the Week
« Reply #52 on: 17/02/2006 22:33:21 »
Cleavage!

More commonly called "rock cleavage" or more properly called either "axial planar cleavage" or "foliation".

Occurs in metamorphic rocks that have been subjected to pressure.  The pressure and heat of metamorphism change the clay minerals in sedimentary rocks into mica (several varieties).  Mica has a distict planar orientation, and it grows in the direction of least pressure- which will be perpendicular to the stress field.



Commonly, bedding planes will fold during metamorphism, also perpendicular to the greatest stress- so the foliation ends up being in the axial plane of the fold, hence "axial planar cleavage".  The amount and orientation of foliation allows the observer to figure out the relative intensity of metamorphism and gives clues as to the true orientation of the original beds.

Subduction causes orogeny.
Old enough to have a grandson
Slow enough to study rocks
Thirsty enough to find a pub

*

Offline Ray hinton

  • Sr. Member
  • ****
  • 476
    • View Profile
    • http://uk.geocities.com/rayhinton56@btinternet.com/photopagetan.html
Re: Geology Question of the Week
« Reply #53 on: 24/02/2006 12:15:18 »
quote:
Wonderbra -
what most men first notice about a woman wearing a wonderbra.

their not very well blessed ?

RE-HAB IS FOR QUITTERS.
its the drugs,y-know.

*

Offline JimBob

  • Global Moderator
  • Neilep Level Member
  • *****
  • 6564
  • Moderator
    • View Profile
Re: Geology Question of the Week
« Reply #54 on: 05/03/2006 01:53:30 »
quote:
Originally posted by Bass



Maybe this belongs in the "Science Photo of the Week" thread, but the reference to cross-beds in this thread made it relevant.

This photo from the Mars Rover Opportunity near the edge of Erebus Crater shows good evidence for the historical presence of water on Mars- note the "festoons" or cross-laminations (curved upward layers) that indicate water-formed ripples.
http://www.spaceref.com/news/viewsr.html?pid=19212


Subduction causes orogeny.



Bass, may I politely disagree. I concur that this is evidence for water on Mars, but the structures to me look to be a series of seasonal dessication cracks that are stacked one upon another. To bad we can't get to the outcrop to determine the accuracy of the interpretation.

And orogeny causes uplift

The mind is like a parachute. It works best when open.  -- A. Einstein

*

Offline Ophiolite

  • Hero Member
  • *****
  • 718
    • View Profile
Re: Geology Question of the Week
« Reply #55 on: 05/03/2006 02:29:56 »
Interesting. I am seeing a cross section through a finely laminated sequence; no cross bedding; no dessication cracks. It is good to know the art of geological equivocation is still alive and well.
Observe; collate; conjecture; analyse; hypothesise; test; validate; theorise. Repeat until complete.

*

Offline JimBob

  • Global Moderator
  • Neilep Level Member
  • *****
  • 6564
  • Moderator
    • View Profile
Re: Geology Question of the Week
« Reply #56 on: 06/03/2006 01:22:46 »


Alright Ophialite (rock or snake?).

The structure just off of the end of the arrow is not a cleavage related feature. It lacks one side of being a closed square. This suggest dessication to me. There are traces of the same type of feature and one whith a chip "wedged" between the to sides of a upturned bed. But I am not going to make any more of this as we will never know for sure.

What bothers me more is the origin of the pellitoidal thingies that are all over the place. Are they desert, wind-generated concreations? Can you think of another explinaiton? Weatherd out of another rock? Or other?  

I am open to all as I know the laminated are faily well explained.

Jim
The mind is like a parachute. It works best when open.  -- A. Einstein

*

Offline Ophiolite

  • Hero Member
  • *****
  • 718
    • View Profile
Re: Geology Question of the Week
« Reply #57 on: 06/03/2006 02:57:03 »
[Ophiolite - ocean rocks welded to continental masses by subduction]
If you will imagine swinging the arrow around in a clockwise direction, till it is vertical, you will find it ends in a narrow column of rock, replete with laminations, slightly displaced from the adjacent blocks. I see post depositional collapse structures. Nothing more. However, you are correct: from this single photograph we are unlikely to reach a firm conclusion.

The small spherules I took to be blueberries, which were observed early on by both (?) rovers. These may be formed as concretion within the rock as a result of groundwater activity, then released by normal erosional processes. For example: http://www.spaceflightnow.com/news/n0406/16blueberries/
Observe; collate; conjecture; analyse; hypothesise; test; validate; theorise. Repeat until complete.

*

Offline JimBob

  • Global Moderator
  • Neilep Level Member
  • *****
  • 6564
  • Moderator
    • View Profile
Re: Geology Question of the Week
« Reply #58 on: 06/03/2006 17:12:43 »
I can go along with collapse structurs. Also, the hematite concreation hypothisis was first on my list. I dared not hope for oolites eroded from a less dense carbonate. And I was taught that ophiolte was a mostly mafic igneous rock with a little metamophic thrown in that is metamorphosed in a subduction that probably failed - example: the highlands of Cuba. I am a rock pounder as well, but of a much ealier vintage.

Good to know I am not alone here.

Jim
The mind is like a parachute. It works best when open.  -- A. Einstein

*

Offline Bass

  • Neilep Level Member
  • ******
  • 1340
    • View Profile
Re: Geology Question of the Week
« Reply #59 on: 08/03/2006 20:52:35 »
Since JimBob brought it up-

GQOTW:  What are oolites and how do they form?

Subduction causes orogeny.
Old enough to have a grandson
Slow enough to study rocks
Thirsty enough to find a pub

*

Offline Ophiolite

  • Hero Member
  • *****
  • 718
    • View Profile
Re: Geology Question of the Week
« Reply #60 on: 08/03/2006 23:10:41 »
Oolites are a component of certain sedimentary rocks. However, I view everything Cambrian and later as superficial drift deposits, so I choose not to answer. Basalts are real rocks, so are eclogites.

JimBob, I will be marginally surprised if you are an earlier vintage than I. For one thing I can remember how warm the summers were in the late Cretaceous! Class of '70. Yourself?
Observe; collate; conjecture; analyse; hypothesise; test; validate; theorise. Repeat until complete.

*

Offline JimBob

  • Global Moderator
  • Neilep Level Member
  • *****
  • 6564
  • Moderator
    • View Profile
Re: Geology Question of the Week
« Reply #61 on: 09/03/2006 01:46:02 »
'66

If I only had a little humility, I'd be perfect.
    ----Ted Turner
The mind is like a parachute. It works best when open.  -- A. Einstein

*

Offline Ophiolite

  • Hero Member
  • *****
  • 718
    • View Profile
Re: Geology Question of the Week
« Reply #62 on: 09/03/2006 02:41:44 »
Damn. You don't live in Texas do you? Or, ever worked for Conoco?
Observe; collate; conjecture; analyse; hypothesise; test; validate; theorise. Repeat until complete.

*

Offline JimBob

  • Global Moderator
  • Neilep Level Member
  • *****
  • 6564
  • Moderator
    • View Profile
Re: Geology Question of the Week
« Reply #63 on: 09/03/2006 02:54:21 »
I do. Never worked for Conoco but had three partners that did. Timko, Lindah, Schweirkert. Obviously, working with them I lived in Houston (ICH!) for 12 years until the worldwide consuling job in my hometown came up.

If I only had a little humility, I'd be perfect.
    ----Ted Turner
The mind is like a parachute. It works best when open.  -- A. Einstein

*

Offline Bass

  • Neilep Level Member
  • ******
  • 1340
    • View Profile
Re: Geology Question of the Week
« Reply #64 on: 22/03/2006 18:11:29 »
Picture of oolites




Subduction causes orogeny.
Old enough to have a grandson
Slow enough to study rocks
Thirsty enough to find a pub

*

Offline JimBob

  • Global Moderator
  • Neilep Level Member
  • *****
  • 6564
  • Moderator
    • View Profile
Re: Geology Question of the Week
« Reply #65 on: 22/03/2006 23:32:52 »
Beautiful picture, Bass. Looks as if it cold have come from the broken well bore core obtained from the Smackover Limestone of the Gulf Coast of the US. Is the limestone pictured Upper Jurassic? If so it would be the ABOUT the same age as the Smackover. Below the Smackover is the mainly aeolian, arkosic Norphlet Sand that is then underlain by the Louann "Salt". This is a series of mixed evaporites (the core sitting on my desk is mostly gypsum) that was deposited during the opening of the Gulf basin.

I am intersted to see how this correlates.


If I only had a little humility, I'd be perfect.
      --Ted Turner
The mind is like a parachute. It works best when open.  -- A. Einstein

*

Offline Bass

  • Neilep Level Member
  • ******
  • 1340
    • View Profile
Re: Geology Question of the Week
« Reply #66 on: 23/03/2006 21:34:28 »
Upper Jurassic Portland Group.  The photo is not mine, but I remembered the distinctive oolites from a field trip eons ago.

Subduction causes orogeny.
Old enough to have a grandson
Slow enough to study rocks
Thirsty enough to find a pub

*

Offline The Silurian Prince

  • Jr. Member
  • **
  • 15
    • View Profile
Re: Geology Question of the Week
« Reply #67 on: 19/04/2006 04:09:41 »
The red is oxidation.  The green is likely evaporite deposits from a hypersaline brine.  Likely gypsum or something like that.  This would be a periodic deposition process that produces the green layers you see in these red bodies. Not to sure about the decomposing plants idea.  Sounds a bit far fetched.  The environment was likely pretty dry.

Enjoy diversity.
Enjoy diversity.

*

Offline lovelesh

  • First timers
  • *
  • 1
    • View Profile
Re: Geology Question of the Week
« Reply #68 on: 02/05/2006 12:54:26 »
Red Sandstone fairly formed in the oxidation environment. It contains Iron oxide and probably comming out from the chemical weathering of Basic o Ultrabasic rocks. This type of rocks form in backarc basins.
Green colour representing Glauconite.
In India Vindhyan sandstone of Central province have both characteristics

lovelesh
lovelesh

*

Offline Bass

  • Neilep Level Member
  • ******
  • 1340
    • View Profile
Re: Geology Question of the Week
« Reply #69 on: 26/07/2006 18:21:48 »
What is a "nick point"?


Subduction causes orogeny.
Old enough to have a grandson
Slow enough to study rocks
Thirsty enough to find a pub

*

Offline JimBob

  • Global Moderator
  • Neilep Level Member
  • *****
  • 6564
  • Moderator
    • View Profile
Re: Geology Question of the Week
« Reply #70 on: 27/07/2006 16:23:31 »
According to the AGI Glossary of Geology ...

No, that is cheating. I am above that (right [}:)])



The mind is like a parachute. It works best when open.  -- A. Einstein
The mind is like a parachute. It works best when open.  -- A. Einstein

*

Offline Bass

  • Neilep Level Member
  • ******
  • 1340
    • View Profile
Re: Geology Question of the Week
« Reply #71 on: 26/07/2006 18:21:48 »
What is a "nick point"?


Subduction causes orogeny.
Old enough to have a grandson
Slow enough to study rocks
Thirsty enough to find a pub

*

Offline JimBob

  • Global Moderator
  • Neilep Level Member
  • *****
  • 6564
  • Moderator
    • View Profile
Re: Geology Question of the Week
« Reply #72 on: 27/07/2006 16:23:31 »
According to the AGI Glossary of Geology ...

No, that is cheating. I am above that (right [}:)])



The mind is like a parachute. It works best when open.  -- A. Einstein
The mind is like a parachute. It works best when open.  -- A. Einstein

*

Offline Bass

  • Neilep Level Member
  • ******
  • 1340
    • View Profile
Re: Geology Question of the Week
« Reply #73 on: 18/08/2006 05:24:07 »
Here's a hint


Subduction causes orogeny.
Old enough to have a grandson
Slow enough to study rocks
Thirsty enough to find a pub

*

Offline JimBob

  • Global Moderator
  • Neilep Level Member
  • *****
  • 6564
  • Moderator
    • View Profile
Re: Geology Question of the Week
« Reply #74 on: 21/08/2006 15:03:18 »
Magnificent picture, Bass. I would like to be there now - temp was 103 F yesterday and more of the sasme today.

Since no one else seems inclinded to answere this, let's keep it amoung ourselves, the pros.

A nick point in geology is derived from the same term in mathematics that denotes the single point where a curve changes slope abruptly.

This term is also applied to the gradient of a stream. If streams flowed over only one homogenious substratum, the gradient curve for the stream would be steep at the head of the stream and shallow at the mouth of the stream. This can occur over a very short distance within a stream's profile.

BUT, since there is a distance longer than a few hundred or thousands of feet in a streams, the substratum varies from soft to hard, ususally by sharp geologic contatcts. (The soft-hard rock interface is relative to each other.)

As pictured, the hard up-stream rock is in contact with a softer down-stream rock and a water fall is produced. The top of the waterfall is a nick point - the inflection point in the stream's gradient.

Streams can go from softer rock formations to harder rick formations: these gradient changes often result in rapids.




The mind is like a parachute. It works best when open.  -- A. Einstein
The mind is like a parachute. It works best when open.  -- A. Einstein

*

Offline ichnos

  • Jr. Member
  • **
  • 38
    • View Profile
Geology Question of the Week
« Reply #75 on: 16/04/2007 12:48:02 »
As described previously the red sediments with green mottles can be attributed to roots within fossil soils. The mottles represent areas of reduced iron, produced from anaerobic decay of organic matter in a fossil soil with a fluctuating water table. I would like to add that EXODUS is WRONG in that just because a sediment is RED does not mean it was formed in arid conditions (CHECK ALFISOL SOILS). Red soils are also found in humid climates and the drab haloed roots or burrows (green  mottles)suggest that the water table fluctuates temporarily. The idea that red = arid is old news - get with it!  [;)]

*

Offline JimBob

  • Global Moderator
  • Neilep Level Member
  • *****
  • 6564
  • Moderator
    • View Profile
Geology Question of the Week
« Reply #76 on: 03/05/2007 01:04:36 »
Which river carries the highest sediment load? This is for the whole world.
The mind is like a parachute. It works best when open.  -- A. Einstein

*

Offline ichnos

  • Jr. Member
  • **
  • 38
    • View Profile
Geology Question of the Week
« Reply #77 on: 03/05/2007 14:54:15 »
Is it in total discharge or per volume water per year or per day?

*

Offline JimBob

  • Global Moderator
  • Neilep Level Member
  • *****
  • 6564
  • Moderator
    • View Profile
Geology Question of the Week
« Reply #78 on: 03/05/2007 17:50:49 »
No. Sediment load is the total solids moved, both the mud and small sands in suspension and larger particles moved by saltation and other methods, e.g., by ligifaction, etc., along the bottom of the stream bed.

The mind is like a parachute. It works best when open.  -- A. Einstein

*

Offline ichnos

  • Jr. Member
  • **
  • 38
    • View Profile
Geology Question of the Week
« Reply #79 on: 03/05/2007 18:50:55 »
yes, what you say is correct, however, the sediment load can vary significantly seasonally. Are you after the river that can carry the maximum possible sediment load at any one time? or the river that carries the highest mean sediment load for say a year? I have asked around if anyone knows the answer (we're academic geologists of one type or another! [???]). There is a suggestion that a river in a glaciated area may carry the highest sed load seasonally but that a river such as the Bramahputra may carry the average highest sed load..  [:)]

*

Offline JimBob

  • Global Moderator
  • Neilep Level Member
  • *****
  • 6564
  • Moderator
    • View Profile
Geology Question of the Week
« Reply #80 on: 04/05/2007 03:07:10 »
Well, then you have already got part of the answer. The Bramahputra-Ganges system has the highest sediment load, month from month. Most people think only of the Bramahputra OR the Ganges, not realizing that they merge 100+ miles from sea, forming a river with the highest sediment load, however you look at it. Also remember that the Bramaputra and the Ganges ARE rivers originating in a glaciated area. Together, they have the highest sediment load season by season.
« Last Edit: 04/05/2007 03:09:27 by JimBob »
The mind is like a parachute. It works best when open.  -- A. Einstein

*

Offline JimBob

  • Global Moderator
  • Neilep Level Member
  • *****
  • 6564
  • Moderator
    • View Profile
Geology Question of the Week
« Reply #81 on: 04/05/2007 03:34:30 »
What type of rocks are these?


The mind is like a parachute. It works best when open.  -- A. Einstein

*

Offline Bass

  • Neilep Level Member
  • ******
  • 1340
    • View Profile
Geology Question of the Week
« Reply #82 on: 11/05/2007 17:10:56 »
JimBob- no one seems to be willing to venture a guess?  Must not be many earth scientists hanging about lately?
Nice, clear photo.  The outer folded layer appears to be either quartz or quarzite (could also be calcareous?).  Can't quite make out the inner rock- even though the white specks (feldspars, clastic fragments?) seem to have no preferred orientation- I would guess sedimorphic (a new geologic term!) - metamorphosed clastic rock. Could also be some sort of subvolcanic igneous- perhaps a latite- but that may be my hard-rock bias showing.
Old enough to have a grandson
Slow enough to study rocks
Thirsty enough to find a pub

*

Offline JimBob

  • Global Moderator
  • Neilep Level Member
  • *****
  • 6564
  • Moderator
    • View Profile
Geology Question of the Week
« Reply #83 on: 11/05/2007 17:35:25 »
Bass - Think gem minerals

I know that is a dead give-away, but as you noticed, there are not too many peopel who were wise in their carrier choice on this site.  [;D]
 
The mind is like a parachute. It works best when open.  -- A. Einstein

*

Offline JimBob

  • Global Moderator
  • Neilep Level Member
  • *****
  • 6564
  • Moderator
    • View Profile
Geology Question of the Week
« Reply #84 on: 16/05/2007 19:11:36 »
The outer one is a PEGMATITE !! - I know that the inner part of the fold is hard to see (it is a high silicate rhyolitie) so if someone got "pegmatite" I wasn't going to carp about it. The highly crystalline nature of the pegmatite can easily be seen. The formation of the crystals on the inner sides of the fissure with crystallization evolving inward until the gap between sides is closed.

Perhaps I'll find some picts that are easier.
The mind is like a parachute. It works best when open.  -- A. Einstein

*

Offline JimBob

  • Global Moderator
  • Neilep Level Member
  • *****
  • 6564
  • Moderator
    • View Profile
Geology Question of the Week
« Reply #85 on: 18/05/2007 02:38:16 »
What place is considered to be the place most damaged by the largest earthquake in recorded history? It was an estimated 9.4 magnitude earthquake. 2004 Indian Ocean earthquake and tsunami was 9.0, and the one this question is about is, by most, considered much larger.
The mind is like a parachute. It works best when open.  -- A. Einstein

*

Offline Bass

  • Neilep Level Member
  • ******
  • 1340
    • View Profile
Geology Question of the Week
« Reply #86 on: 18/05/2007 16:51:02 »
I wasn't around for the largest, but I was in Alaska for 2nd largest in 1964. 
Old enough to have a grandson
Slow enough to study rocks
Thirsty enough to find a pub

*

Offline JimBob

  • Global Moderator
  • Neilep Level Member
  • *****
  • 6564
  • Moderator
    • View Profile
Geology Question of the Week
« Reply #87 on: 19/05/2007 21:26:43 »
Since the Indian Ocean quake Alaska is now #3. But dang, Bass, you are almost as old as I am. The pictures of the damage on TV were in black and white!

For a hint on the question, refer to your "where in the world."
The mind is like a parachute. It works best when open.  -- A. Einstein

*

Offline Bass

  • Neilep Level Member
  • ******
  • 1340
    • View Profile
Geology Question of the Week
« Reply #88 on: 20/05/2007 17:30:01 »
I wasn't around for the largest, but I was in Alaska for 2nd largest in 1964. 
Sorry JimBob, I didn't phrase that very well.  I was but a young lad, and remember the b&W pictures on a very small neolithic TV.  What I meant was that I wasn't in the vicinity of this earthquake, I was way too far north- and news traveled much more slowly in Alaska during those days.
According to the USGS, Alaska is still #2.
« Last Edit: 20/05/2007 17:40:31 by Bass »
Old enough to have a grandson
Slow enough to study rocks
Thirsty enough to find a pub

*

Offline JimBob

  • Global Moderator
  • Neilep Level Member
  • *****
  • 6564
  • Moderator
    • View Profile
Geology Question of the Week
« Reply #89 on: 28/05/2007 20:52:43 »
The Lisbon earth quake of 1755 is the one I was looking for. 35% of the population was killed in Lisbon, 10,000 in Morocco. The resultant tsunami affected southern England, Galway, Ireland and the Antilles. It is estimated by some seismologists to have been well over 9 on the Richter Scale.
The mind is like a parachute. It works best when open.  -- A. Einstein

*

Offline Bass

  • Neilep Level Member
  • ******
  • 1340
    • View Profile
Geology Question of the Week
« Reply #90 on: 29/05/2007 03:46:14 »
Oops- thought you were referring to the Chilean earthquake (M 9.5) in May 1960.
Old enough to have a grandson
Slow enough to study rocks
Thirsty enough to find a pub

*

Offline JimBob

  • Global Moderator
  • Neilep Level Member
  • *****
  • 6564
  • Moderator
    • View Profile
Geology Question of the Week
« Reply #91 on: 02/06/2007 02:27:06 »



Any idea?? This is probably too easy BUT spec-tack-u-ler

The mind is like a parachute. It works best when open.  -- A. Einstein

*

Offline Bass

  • Neilep Level Member
  • ******
  • 1340
    • View Profile
Geology Question of the Week
« Reply #92 on: 04/06/2007 17:10:47 »
aerial photo of desert landscape with flat-lying beds.  Somewhere in Utah perhaps?  Is the white snow?  Can see a road in the upper left corner.
Old enough to have a grandson
Slow enough to study rocks
Thirsty enough to find a pub

*

Offline JimBob

  • Global Moderator
  • Neilep Level Member
  • *****
  • 6564
  • Moderator
    • View Profile
Geology Question of the Week
« Reply #93 on: 10/06/2007 03:55:31 »
The satellite picture is of an area about 95 mile SW of Muscat Oman. Bass is correct about the desert landscape and sediments. But the wadi (valley) cutting across the shot is pretty obviously in a thrust fault expression. The white is possibly salt. There is a lot exposed here.
« Last Edit: 10/06/2007 03:58:52 by JimBob »
The mind is like a parachute. It works best when open.  -- A. Einstein

*

Offline Sarah Elizabeth

  • Jr. Member
  • **
  • 13
    • View Profile
Geology Question of the Week
« Reply #94 on: 09/01/2008 18:10:13 »
as to the red sandstone, its very common in the uk,  because we used to be on and around the equator, at around 50  degrees we were in a desert environment. the action of the sun made the rock much darker red in colour and the green has got to be copper because green marks arent left by any common tree from  the tertiary when the climate was that of a desert...the sandstone deposited in the uk has laminations if found on a grand scale.. the fact that the red sandstone has laminations ( deposited in dunes ) means that a tree could not survive in a sand environment alone.  its got to be from the element. it wouldnt be discolouring, because in sandstones the only form of discolouring is bleaching, where by the action of water removes the oxide and leaves it white !

*

Offline Sarah Elizabeth

  • Jr. Member
  • **
  • 13
    • View Profile
Geology Question of the Week
« Reply #95 on: 09/01/2008 18:12:21 »
did you know that after the big lisbon earthquake of 1755 the only building in the city found to be standing was a brothel .

*

Offline Sarah Elizabeth

  • Jr. Member
  • **
  • 13
    • View Profile
Geology Question of the Week
« Reply #96 on: 09/01/2008 18:19:50 »
to the comment about alfisol soils id like to add that soils are a completely different matter as red, iron-rich subsurface horizons are only characteristics of soil and a red desert sandstone is of that name because it is lithified sand grains cemented together by silicon or various rarer types, which have been turned red ONLY by the action of the sun. If we are talking about soils its a completely different matter !

*

Offline Sarah Elizabeth

  • Jr. Member
  • **
  • 13
    • View Profile
Geology Question of the Week
« Reply #97 on: 09/01/2008 18:29:53 »
Which river carries the highest sediment load?   .... i reckon its got to be the Amazon ! i know that it transports 2 billion tonnes of particles from the andes every year over to Africa. the Andes is the fastest growing mountain range and my favourite :) apparently, according to extremescience.com For the last century the  Amazon and Nile  have been fighting over the title for the  world's longest river. the length of them both varies across time, not sure how, but it says that the amazon carries the most amount of water.  now thats got to be something... ?

*

Offline Sarah Elizabeth

  • Jr. Member
  • **
  • 13
    • View Profile
Geology Question of the Week
« Reply #98 on: 09/01/2008 18:38:34 »
What type of rocks are these?





you know, this is a really interesting picture : the rock's awesome ! im actually going to have a guess at its formation, but id like to know where the location is...?  the rock in the middle is a hard rock but id guess its been metamorphosed , it probably was a mudstone at the bottom of a deep sea and then the calcarous stuff was laid on top,i think the fact its now on land would suggest isostasy was at work and it used to be in a warm tropical climate where the calcium carbonate limstone was laid down. it looks like it has a very high silica content but that could be metamorphosed Calcium Carbonate to make it marble- like .do you know what the rock is btw, ?

*

Offline Sarah Elizabeth

  • Jr. Member
  • **
  • 13
    • View Profile
Geology Question of the Week
« Reply #99 on: 09/01/2008 18:51:06 »
the rockies are running along the conservative plate boundary known as the san andreas fault, or the massive tear in the ground between the american plate and the pacific plate.so it is a plate boundary. theyre stil growing because the plates are active