If you consider it as a continental-scale process with a rift system like the EARS consisting of many branches, some of them developing into failed rifts, the process probably can take longer than 60 million years. See e.g. the Jurassic to Cretaceous rift basins of Sudan - if today's rift systems in East Africa have formed in continuation of certain (failed) Mesozoic rifts you would have a continenctal-scale process lasting more than twice as long. How long it takes from the intial phase to oceanic crust formation probably depends on various facors, such as rate of divergence, thickness, compositon/age of the continental crust subjected to rifting.

You are rigth, but I am more interested in the continental-rift to oceanic crust formation case. Is there any well-studied example lasting several tens of m.y.?

Papers by Luyendyk and his team and no doubt others document that the part of the West Antarctic rift system through Marie Byrd Land started extending about104 Ma, and then New Zealand/Campbell Plateau started drifting away about 80 Ma. But the rifting continued in Ross Sea, with possible early Cenozoic rifting in the middle of Ross Sea and definite Eocene-Oligocene large rifting in Western Ross Sea opposite Adare Trough spreading. And the Terror Rift is still active.

For Continent to Ocean, you might want to look at the north Atlantic: the rifts in eastern USA. But I don't know the timing.

Continuous rifting for 60 my sounds long. However episodic rifting can last for 250 my, eg in the NE Atlantic.

Rubén,

probably the best studied continental margin is the Newfoundland - Iberia conjugate system. There is a wealth of data coming from the ODP and DSPD projects. You should consider having a look at their summaries. These scientific missions have drilled several sites at both margins, as well as acquired many km of seismic profiles. Actually, most of the existing models for rifting and oceanic spreading come from the data obtained for this conjugate system. More indirect evidence comes from the study of 'well' preserved ocenanic remmants in orogenic belts such as the Alps, Dinarides, Oman, Alaska, ...

You could consider having a look to the models made by Gianreto Manatschal and co-workers. They have a large data set mainly coming from Central Alps of Switzerland and Italy. In their works they present isotopic and biostratigraphy ages to constrain the timing of rifting and oceanic spreading. Whether you agree or not with their models it's fine, but they manage a large data set on timing. Another interesting indirect source of information comes from the Western Alps. A nice review is presented in the book "The Western Alps, from rift to passive margin to orogenic belt" by Pierre-Charles de Graciansky, Dave G. Roberts and Pierre Tricart". I am currently working the Eastern Alps, but I anyway find this text very very illustrative and it contains a fantastic compilation of many many years of work as well as constrasting views.

Going back to your question, rifting to oceanic spreading can last for many tens of Myrs. It depends on the case, but regarding the Pyrenean Rift - Bay of Biscay, final rifting episode started at about Kimmeridgian times (ca.155 Ma) and mantle exhumation - oceanic spreading halted by Santonian(?) times moreless (ca. 84 Ma). So for this case, yes. Consider also, as mentioned above by E. Lunding, that rifting of the Variscan edifice actually started by Permian - Triassic (Pangea break up), stopped during Early-Middle Jurassic and was resumed in Late Jurassic. So the whole process of rifting and spreading can last for way more than 60 Myr.

Hope you consider my answer useful,

Pablo

I forgot to mention in my last post whether continental break up can be magma-assisted (or magma rich) vs. magma poor.

There are many differences between both and timing is also variable.

Another idea to find time constraints for the transition from continental rift to sea floor, especially a minimum duration, is to study very young rift basins and oceans. A good example might be the Afar triple junction where the Red Sea, Gulf of Aden, and northern part of the (Main) Ethiopian Rift join.

See e.g. the paper of Bosworth and colleagues (2005) on the timing of Red Sea and Gulf of Aden rifts: Accordling to the volcanic history (and further geological evidence) the phase of continental rifting (syn-rift phase) started during the Oligocene and ended during the Miocene. It took between 10 million years (Gulf of Aden and Gulf of Suez) and 22 million years (southern Red Sea).

http://scholar.google.de/scholar?cluster=16258297023318432056&hl=de&as_sdt=0,5

Thanks for your help. I am reading some papers about the Afar triple junction. I have started with the 2006 Special Publication of the Geol Soc London (Yirgu et al.). Maybe there is something esle out there from other old rift systems.

Pablo, I will look up for the differences between magma-assisted and magma poor rifts, thanks!

Just to give you an idea.....

The oldest volcanic rocks in relation to the onset of extension along the future Izmir-Ankara branch of Neotethys are late Ladianian in age Tekin U.K. & Goncuoglu,M.C. 2007. Discovery of oldest (late Ladinian to middle Carnian) radiolarian assemblages from the Bornova Flysch Zone in western Turkey: Implications for theevolution of the Neotethyan Izmir-Ankara Ocean. Ofioliti, 32/2, 131-150) The oldest oceanic pillow-lavas within the Izmir-Ankara suture belt are late Carnian in age (Tekin U.K., Göncüoglu M.C. and Turhan N., 2002. First evidence of Late Carnian radiolarians from the Izmir-Ankara Suture Complex, central Sakarya, Turkey: implications for the opening age of the Izmir-Ankara branch of Neo-Tethys. Geobios, 35/1, 127-135).

Accordingly, the time-span you are asking is about 10-12 Ma for the Izmir-Ankara Ocean. However, pleace notice that there are numerous controls and the data in literature is case-specific.

For an ancient example, during Neoproterozoic break-up of Rodinia, the eastern (present-day coordinates) margin of Laurentia experienced an ~200 m.y. history of rifting that occurred in two major pulses. The first episode, over the period of ca. 765-680 Ma, involved intracontinental rifting characterized by bimodal volcanism and intrusion of A-type granitoid plutons. There appears to have been a hiatus in activity until extrusion of basalt and minor rhyolite at ca. 570-555 Ma, during relatively rapid extension that led to continental break-up and opening of the Iapetus Ocean. A few pertinent references are: Aleinikoff et al., 1995, American Journal of Science, v.295, p.428-454; Fetter & Goldberg, 1995, Journal of Geology v.103, p.313-326; Tollo et al., 2004, Precambrian Research, v.128, p.3-38; Badger & Sinha, 2004, Geol Soc America Memoir 197, p.435-458.

Maybe you can have a look at the review paper by Ziegler and Cloetingh (Earth Science Reviews, 64, 1-50, 2004). The duration of rifting is highly variabile and they provide a quite long list of different examples in both volcanic and non-volcanic settings.

The Maximum allowable recorded age is 252 million years in one small

location in the Atlantic, and One small area of the Pacific as recorded in

the magnetic reversals of the cooling basalt of the ocean floors.

The youngest would be the Afar Triangle, and the Dead Sea ( That are

Obvious).

You could compare Oceanic ( Iceland ), with Continental ( Afar Triangle )

and look for similarities and differences. Also observe that the majority

of the Continents are in the Northern Hemisphere, so as the planet

increases in surface area and volume, the continents open up

in a manner similar to the Gull-Wing Doors on a Delorean, but with

added attributes like surface stretching ( Basin and Range of the

Western US ) , and mid-continental surface corrections for curvature,

( Parallel Mountain-Basin Pairs ) . Look for Mountains with shallow

basins parallel to the Range, with a semi parallel River like the

Ganges.

The " illusion of Subduction " is also an attribute of a growing planet,

where the materials deep under the Continents provide a material

source that creeps toward the spreading ridges. This has thinned the

continental crust from about 133 km down toward about 39.8 km thick,

on average, with the requisite bending of the rock layers at the margin

due to differential vertical motions of the Oceanic crust, and Continental

crust. You can model this with a Magazine interleaved with a thick

phone book, and both held out at arms length. it will not be long

before the heavier phone book gets lower, while the magazine rises,

thus creating bending, and the illusion of subduction.

Most Geologic processes can be modeled using reams of paper

of different thicknesses, while letting gravity do the work on your

outstretched arms trying to hold up the paper.

The expanding earth hypothesis is simply not true. I've addressed parts of this before to Clarke posts so will not bother here. I'm only posting in case some of the scientists reading this do not have much earth science background.

For a tectonic theory to be valid, it must be valid for all planets in the various stages

of their evolutionary processes. Simply taking Magazine Pictures of Planets of

Various sizes and lining them up from smallest to largest and observing the

areas of older surfaces compared to areas of younger surfaces will show that

planets have both types. The conclusion is that whatever the processes,

the surface reflection of those internal planetary processes is written in stone

and ice on a stretched planetary surface of varying ages.

Smaller " planets ' like Ganymede, and Enceladus are very good at preserving

the stretched planet surface appearances.

Either Plate Tectonics, or Growing planet theory is valid for planets of

all sizes and ages up thru the Earth sized planets and beyond, or,

something else is valid. We know that the Earth has and still is accreting

materials from space, though the quantity is small on an annual basis.

We know that stars grow larger, because we can see star forming regions

with our very large telescopes.

The processes that apply for one scale of objects must be similar to,

or an evolutionary derivative of the processes are larger, and

also smaller Cosmic Scales.

The Earth only appears unique in that it has allowed Life to persist

on its surface for such a protracted period of Geologic Time, while at the

same time evolving the mediums that life can exist and thrive within.

First warm spots, then ice, then oceans, then land, then air.

The sizes of the animals also reflect the changing internal conditions

of the planet, but it is an inverse relationship where animals became

very large, and then gradually dwindled in size as the applied gravitational

forces became larger.

Geology and Geophysics is one of the few sciences where we must infer

the contents of the Book, by looking carefully at its cover, and the covers

of all the other books in the neighborhood. Plate tectonics infers that the

Book with the Blue Cover is some how unique when compared to

all the others. The Blue cover is just an evolutionary stage, all the

Books have covers, all of them are cracked. All tell a similar tale,

be we are so preoccupied by the book with the blue cover that we do

not really see what is inside all of them, and how they change with time.

This reminds me of a thread on ResearchGate about whether dark energy has anything to do with plate tectonics. There are several what appear to be high-quality answers (answers are "No") and then a couple by a Russian scientist with a high RG score, higher than many serious scientists (including me). She with others self publishes on Research Gate that dark energy triggers earthquakes that in turn trigger giant whirlpools that sucked in Malaysian Flight 370. Some of her references were to fiction by Edgar Allen Poe, and there is some discussion of the Bermuda triangle having giant whirlpools (that said, there is a massive amount of methane hydrate on Blake Ridge and elsewhere which is within the so called Bermuda triangle, and I wonder if it is possible to have a large enough release to affect the surface: would probably have to be a release from a submarine slide).

I think this "scientist" has a RG score of about 33. RG is going to have to rethink the way they give "credibility". I never joined Facebook or any other social media until I joined RG, which I joined a few months ago because it was suggested for a promotion. So, I long though things like how many "friends" were kind of sad, although I'm impressed with Shakira's 70 or 90 million.

If anyone beside Michael need me to post a few major flaws in expanding earth, let me know and I will do so again. One could start with basic physics. Then, age of earth. Then, well-documented subduction and earthquakes. Then, GPS velocities.

Agree with Christopher.

Better to stop the facebook-type "like/unlike" promotion in RG.

Discussions and comments are good enough.

Pseudoscientific ones can be ignored ore answered without giving a chance to offend.

In 2003, There was a recalibration of the roughly 1200 reference points

worldwide that are (were) used to reference the Global Positioning System.

They wanted to see magnitude and direction of the Movement of the 1200

points in millimeters per year in X, Y, and Z. All of the points moved, and

about 20 % moved excessively in Delta Z to be useful, and when plotted

those 20% did not lie on the somewhat straight line.

However 927 point lay on a Delta Z straight line between minus 8 mm per

year of vertical movement, and plus 16 mm of vertical movement.

Notice it is not symmetrical, about 1/3 of the points went down, and about

2/3 of the points went up. The Average and the midpoint were at

plus 4.15 mm, and 4.17 mm of upward vertical movement. implying a

gradual increase in the Radius of the Earth currently of roughly 4 mm

per year. Now most of the points sampled were continental

points, and some were points on Islands, and so the Surface of the

ocean Floor is decidedly under represented in this GPS sampling.

Now of the 927 useful points, they selected only 157 points that

lay between minus 4 mm and plus 4 mm, centered on zero

vertical movement and threw out all the rest for use as a vertical

check of vertical motion.

Even though it is frustrating that the Data for a very gradual increase

in Earth's Radius was available, I can not really blame them for

eliminating those points as GPS is used primarily for Surveying the

Earth, and you do not need your reference elevations needing to

be reset by 1 mm four times a year. Wallah - No Vertical change.

Once you have restricted the vertical Data to Sum to Zero, the rest is

just how far North, South, East or West and how fast each continent is

moving, and in which direction is it rotating.

Those are vectors that are plotted on motion maps of the Earth.

Actually if you think about it, there is no logical reason why a planets

surface should be constrained to only two dimensions of motion

if there is any motion of continents what-so-ever. If it has

Two dimensions of motion, then it will have three dimensions of

motion. And if a Planet is still Accreting any material from space,

or receiving any energy from space, it will change its radial dimensions.

On another topic I was informed that a Neutron changing into a

Hydrogen Atom will have a 10^39 increase in Volume. If a

Heavy isotope Decays into lighter isotopes, step by step with

production of helium at each step, there will be an increase in Volume.

The gradual process where the earth moves denser materials

toward its core and lighter materials toward its surface will

lead to a decompression increase in volume because 80 % of the

Earth's materials are lighter elements of Silicon and oxygen, ( SiO2 ).

My calculations predict that the Earth should be increasing at 23.4 mm

per year, but the GPS Data showed only 4.15 to 4.17 mm.

In short the area under the continents is supplying materials to the

area under the ocean floors, thus the ocean floors are rising at a

rate that is faster than the net rise of continents. The planet is thus

undergoing Iso-Dynamic Equilibrium ( redistribution of materials )

induced by gravity. That redistribution of materials is evident in

the bending of the rock at the margins between thicker continental

crust, and thinner oceanic crust where the oceanic crust rises, and

the continental crust settles. Thus subduction is an illusion

created by differential vertical motions of materials of different

densities. Basalt is denser than Granite.

The rate of Delta R = 23.4 mm/ year multiplied by 2 Pi can give use

a summation of all of the rifting rates combined world wide.

However rifting rates in the Southern hemisphere will be faster than

in the Northern hemisphere because of northward Continental

motions. The Delta R was about 3 mm per year 252 MYA.,

but has been increasing.