Second oldest place on Earth?

Bob · Post by **Bob** » Tue May 19, 2009 3:53 pm

EB wrote:Anybody know if they're talking about OUR little patch of desert pavement in Nevada?

You mean the patch under Larry's hat?

Simon of the Playa · Post by **Simon of the Playa** » Tue May 19, 2009 4:18 pm

http://farm4.static.flickr.com/3417/353 ... a1c679.jpg

chiefdanfox · Post by **chiefdanfox** » Tue May 19, 2009 5:01 pm

Desert pavement is not necessarily all old. Think of it sort of like a cobblestone street, with a mixture of cobbles and fine particles in between. They happen quite frequently in a wash. In desert areas the older pavement characterized/aged by the presence and depth of "rock" or desert varnish on the rocks and soil. Attached is a nice little report about rock varnish.
http://eduscapes.com/nature/rocvarnsh/index1.htm

franklampard · Post by **franklampard** » Wed Jun 03, 2009 12:37 am

The American desert is a world-class destination all by itself, of course. It's such an iconic setting, familiar from Western movies, music videos, and car ads, that it feels like home even the first time you go there. Any place in the desert is special, but there are really noteworthy sites near Las Vegas. As you arrive, look around and drink in the sight of endless stone.

Las Vegas Valley is a downdropped basin typical of hundreds in the Basin and Range, the geologic province that extends over all of Nevada and a little beyond it on all sides. Over the last 25 million years or so, the Earth's crust here has been stretched in an east-west direction to around 150 percent of its former width, and the surface rocks have broken into strips of mountains running north-south. As a result the hot material beneath has bulged upward, turning Nevada into a high plateau rich in metal ores and geothermal energy. Numerous earthquakes have been recorded there during this century as the area's tectonic activity continues.

ygmir · Post by **ygmir** » Wed Jun 03, 2009 6:56 am

franklampard wrote:The American desert is a world-class destination all by itself, of course. It's such an iconic setting, familiar from Western movies, music videos, and car ads, that it feels like home even the first time you go there. Any place in the desert is special, but there are really noteworthy sites near Las Vegas. As you arrive, look around and drink in the sight of endless stone.

Las Vegas Valley is a downdropped basin typical of hundreds in the Basin and Range, the geologic province that extends over all of Nevada and a little beyond it on all sides. Over the last 25 million years or so, the Earth's crust here has been stretched in an east-west direction to around 150 percent of its former width, and the surface rocks have broken into strips of mountains running north-south. As a result the hot material beneath has bulged upward, turning Nevada into a high plateau rich in metal ores and geothermal energy. Numerous earthquakes have been recorded there during this century as the area's tectonic activity continues.

maybe I'm wrong, but, IIRC, the ranges in the great basin are "compression ridges".........the crust there is thin, but, the mountains are formed from movement and resulting compression of the north american plate and/or pacific plate, and interactions thereof?.......
Would not "stretching" tend to create volcanic activity regarding mountains?
Most I've seen out there are differing rock strata pushed upwards, much of it limestone, etc, standing on edge almost.
Most of the ranges are (relatively), north/south oriented, the plate movement is east/west.

Just wonderin'..........

Isotopia · Post by **Isotopia** » Wed Jun 03, 2009 10:28 am

the Earth's crust here has been stretched in an east-west direction to around 150 percent of its former width

[geek spiel]

Oh, much more than that.

the ranges in the great basin are "compression ridges".........the crust there is thin, but, the mountains are formed from movement and resulting compression of the north american plate and/or pacific plate, and interactions thereof?.......

That last part of it is applicable to ranges west of the Great Basin and north of Point Arena, CA. Generally speaking tectonic interaction has little contribution to the geophysics of the Basin and Range.

Away from the boundaries of tectonic plates, one of the main drivers of basin dynamics is that it sits atop the mantle's uppermost cool and dense layer â€” the lithosphere â€” which is what is actually spreading. This lithosphere in turn is relatively thin compared to many other flat continental areas of the world. The thin lithosphere means that the underlying, heat convecting, asthenospheric mantle is closer to the plate surface which is one of the reasons that Nevada has so many geysers and hot pools.

As I understand things there is compressional activity that gives rise to the ridges (or horsts) but its working in tandem with the fault blocking which comes about from a spreading of the crust. Uplift is often expressed on the westward facing side of a ridge while the gentler, more gradual sloping due to fault block spreading is expressed on the eastern edge of a range.

As a result the hot material beneath has bulged upward, turning Nevada into a high plateau rich in metal ores and geothermal energy.

This is the generally accepted theory and one held by folks I know who are more versed in the subject than myself. However, there's a relatively new idea floating around out there that suggests that the uplift is actually being caused due to detachment of dense lithospheric mantle from the overlying crust causing the latter to bob higher. This in turn causes uplift at the Earth's surface. Basically its a mechanism that runs 180 degrees from the conventional wisdom. Stand by for a very lively dog fight in the years ahead as this model starts gaining more traction.

[/geek spiel]

BAS · Post by **BAS** » Wed Jun 03, 2009 10:56 am

Too much information too early in the day for me... brain shutting down!

SilverOrange · Post by **SilverOrange** » Wed Jun 03, 2009 1:49 pm

Spammer cutting and pasting. http://geology.about.com/od/geology_nv/ ... eology.htm

Post by **AntiM** » Wed Jun 03, 2009 1:57 pm

You'd have liked the spam links I edited out. One more and he's bounced. My fault for treating him like a real person. I didn't make the same mistake the second time.

theCryptofishist · Post by **theCryptofishist** » Thu Jun 04, 2009 7:33 pm

You get him, AntiM!

Deb Prothero · Post by **Deb Prothero** » Sat Jun 06, 2009 1:33 pm

Stand by for a very lively dog fight in the years ahead as this model starts gaining more traction.

[/geek spiel]

Ain't eplaya great? You come here for a bit of fun and communication and you get to learn something too. Thanks sincerely Isotopia for sharing.

Now where's the beer and popcorn, I wanna watch the fight.

Apollonaris Zeus · Post by **Apollonaris Zeus** » Mon Jun 29, 2009 4:10 pm

But where is the oldest Landscape on earth???

The Negev is much easier to study then this place and it may hold the old undisturbed surface on earth.

Karlene · Post by **Karlene** » Thu Nov 12, 2009 10:13 am

Well the singularity of what is oldest is relative and subject to change. The unnamed spot in Nevada was once considered the oldest undisturbed, ancient surface up until recently. When I was in college taking geology the oldest known rock was dated in Godthab Fjord, Greenland. The Archean gneiss there was dated out to around 3.8 billion years old using Sr-87 and Sr-86 isotopes. That has since changed and now the new record holder being the Acasta Gneiss of the Slave *craton in northwestern Canada which dates out to 4.031 Â± 0.003 billion years.

I love it when you talk like that.......

theCryptofishist · Post by **theCryptofishist** » Thu Nov 12, 2009 10:49 am

*dashes out to tackle hug Karlene then hesitates when she realizes she's looking for Karine. slinks away, embarassed.)

Second oldest place on Earth?

Re: Second oldest place on Earth?

BM is for learning