Geologists confirm the East African Rift has opened up 28' during a recent earthquake. I wish to examine all the major rift valleys on earth and show, they are proof the nearly all continents are being torn apart along these seams. And some fill with ocean water and some with lava.
Satellite images show that the Arabian tectonic plate and the African plate are moving away from each other, stretching the Earth's crust and widening the southern end of the Red Sea, scientists reported in this week's issue of journal Nature.
Last September, a series of earthquakes started splitting the planet's surface along a 37-mile section of the East African Rift in Afar, Ethiopia.
Using the images gathered by the European Space Agency's Envisat radar satellite, researchers looked at satellite data before and after these activities.
I drew two maps of the planet using very simplified lines. It is sometimes easier to see things in a schematic design rather than in great detail. One thing that has always puzzled me is how rift valleys form in the first place. Many people, thanks to the Leakey family's heroic research into the origins of humans, are aware of the East African Rift Valley. This famous valley has all the characteristics of rift valleys: it is lower than the sea in most places, it tends to have many different climate zones within the rift ecosystem, it is very long and it is splitting something nearly in two and the future of many rift zones look as if they will fill with ocean waters.
The East African Rift Valley, like the Dead Sea Rift Valley or California's Imperial Valley, has a long daisy-chain of increasingly rancid lakes. The deeper the rift valley, the saltier and more toxic the lake. The Dead Sea is famously salty. So is the equally aptly named Salton Sea in California.
The Eastern hemisphere shows Africa's east coast being sliced off as if Saudi Arabia were a cleaver, the point where it strikes Africa as right at the beginning of the great rift valley that connects all the lakes in East Africa as well as the headwaters of the Nile, the great river that flows north to the Mediterranean Sea. The section that is being sliced away from Africa is a larger version of Madagascar, the tropical island in the south. It is obvious that it once was part of the mainland, the jigsaw puzzle interface is quite clear as well as the flora and fauna are all African and our lemurian relatives still roam free there, protected when their part of the jungle became an island 20 million years ago.
If one looks across the Pacific Ocean, one can see Australia's Tasmanian Island separated the same way with Australia moving north while the island drags behind more and more as what was once a rift valley becomes connected at both ends by the ocean.
This is true of Ceylon (Sri Lanka) and India: India moved ahead while the rift between both places widened until the ocean filled in.
Looking at the Western Hemisphere, one can clearly see California is a great rift zone, too. Only nothing is 'splitting' it like Africa and Arabia. Instead, it is tearing apart at the bottom and moving northwards. Baja California is already nearly surrounded by sea and in the not too distant future, all of the Central Valley will flood from the already deepening opening in the San Francisco Bay all the way down to the Gulf of California.
A very similar situation is developing, more belatedly, from Seattle, south. Vancouver Island already has separated. It is not unusual to see smaller fragments breaking off before great hunks peel away, it seems.
From the previous article:
Over a period of three weeks, the crust on the sides of the rift moved apart by 26 feet and magma—enough to fill a football stadium more than 2,000 times—was injected along a vertical crack, forming a new crust.
"We think that the crust and mantle melt slowly at depths greater than 10 kilometers [6 miles], where it is hotter, forming magma (molten rock)," said Tim J Wright, study co-author, a Royal Society University Research Fellow. "This magma rises through the crust because it is less dense than the surrounding rock.”
Ah, the magma rising issue! Yes, there is lurking just below the surface, this hot stuff that is very dangerous as well as life-giving. Many of the rift valleys have volcanoes who signal the destructive forces lurking just below. Unlike zones where the continents collide with other plates moving under and over each other, the 'Ring of Fire' situations that cause mountain-building, the rifting action is the earth sinking and tearing. This happens often very close to mountain-building.
For example, in California, the rifting is due to the northward movement of the Pacific Plate while the Atlantic deep ocean rift is driving the North American continent due west.
Researchers from Britain, France, Italy and the U.S. have been observing the 37-mile long fissure since it split open in September in the Afar desert and estimate it will take a million years to fully form into an ocean, said Dereje Ayalew, who leads the team of 18 scientists studying the phenomenon.
The fissure, now 13 feet wide, formed in just three weeks after a Sept. 14 earthquake in a barren region called Boina, some 621 miles north east of the capital, Addis Ababa, said Dereje.
And indeed, they could be right. Smaller rifts that shave off lesser portions often fill with water! The Red Sea is such a rift. We suspect Africa is pushing into Europe but at the same time, we are troubled to see these several rift valleys forming, one right next to the other! For just to the east of the Red Sea is the Jordan Valley Rift! It has one of the deepest rifts on earth: the Dead Sea. This is, of course, also one of the hottest places on earth. This long, narrow rift valley is probably going to split the Middle East off and if it fills with ocean water, it will be a mirror of the Persian Sea and the Red Sea on either side.
Our aim is to understand one of the fundamental processes occurring on our Earth, namely the break-up of continents. But there are also immediate economic, environmental and cultural objectives. We hope to identify possible geothermal fields in the Rift. Oil and geothermal exploration geologists also need to know about the embryonic stages of continental break-up to work out how to discover and exploit reserves along other continental margins where plates have successfully rifted, e.g. the oilfields offshore west Africa. The Rift is environmentally hazardous and our studies will help in both earthquake and volcanic risk assessment. The region of Afar is an area closely linked to the development of Man. Anthropologists, archaeologists and geographers, in their studies of early Man and his interaction with the environment, need to know about the active processes of rifting; the type of faulting; the amount and timing of crustal subsidence and uplift; the distribution of volcanic centres and their associated volcanic rocks.
After thinking about all this for 40 years, I think I can venture some interesting thoughts about rift valleys: they are not only the harbors of life during terrible times of change, they are not only the cradle of most species that live on land (or in the sea rift valleys, ditto!). They are also nearly the death of all living things not once but repeatedly!
This is because the fate of rift valleys isn't so simple. They don't all fill with water, peacefully!
The Boina (Gambouli) fumarole field immediately north of Lake Abbe (also known as Lake Abhe) is located within Plio-Pleistocene basaltic rocks of the Afar stratoid series (CNR-CNRS, 1975). Boina was included in the Catalog of Active Volcanoes of the World (Richard and Neumann van Padang, 1957) based on its geothermal activity. The location listed by the Catalog of Active Volcanoes of the World is mislocated from a 1939 map. The fumaroles are located in a 7-m-deep funnel about 300 m above the surface of Lake Abbe and about 1 km NE of its shore; they are visible and audible from a distance.
Emmel, B.; Jacobs, J.:
Combined titanite and apatite FT data were used to calculate denudation rates. Samples from the paleo western margin of Madagascar along the N-S striking Pan-African Ejeda shear zone give above-average denudation rates (100-205 mMa-1) during Carboniferous times. The shear zone was probably reactivated during this times. In contrast the calculated denudation rates for samples from the interior of the island are moderate (25-120 mMa-1). Vitrinite reflectance data from the Sakoa coal area as well as titanite and apatite FT data imply that during the Permo-Triassic rifting, the areas along the paleo western margin that previously underwent fast denudation were buried by a sedimentary cover of up to ∼4.5 km. At this time, a graben developed further inland along the NW-SE striking transcontinental Bongolava-Ranotsara shear zone (BRSZ). Modelled time-temperature paths indicate that the area within the BRSZ remained cool and unaffected since Carboniferous times whereas the samples northeast and southwest of the BRSZ suggest phases of differential cooling during Permian-Triassic times. Seismic data from the Morondava basin indicate that during the Middle Jurassic drift between Madagascar and East-Africa a rift jump towards the west occurred.
I included this long quote because of the observation the rift 'jumped' to the west. Namely, these events happen sometimes in great jerks, not in just incremental inching along over long periods of time. One thing that literally gives a jolt are when large celestial objects come crashing into the earth, jangling the entire planet.
In an earlier article, I also noted how continents don't merely move but, like many things in nature, they rotate as they travel. This is probably due to convection paths in the mantle. The other force at work is the come together/split apart cycle the earth has shown over the eons. We are in the end staged of the 'coming apart at the seams' cycle which is why I propose that ALL the continents are continuing to come apart.
Namely, where the Mississippi, the St. Lawrence Seaway, the Amazon, the Nile/East African Rift Valley, the Jordan Valley, the rivers between Uraguay and Argentina, these are one of many rift zones. Perhaps the Rhine valley is one, too!
The St. Lawrence rift system (SLRS) is an active fault zone where reactivation of Iapetus-related structures is believed to occur. The rift faults fringe the contact between the Grenvillian basement to the NW and the St. Lawrence Lowlands to the SE. The SLRS trends NE-SW and forms a half-graben that links the Ottawa-Bonnechère and the Saguenay River grabens. Rift faults are NE- and NW-trending and marked by breccias and cataclasites. The paucity of isotopic age data and the absence of rock strata younger than the Ordovician make it difficult to constrain the timing of the different faulting increments. Field relations suggest that faulting is younger than the Charlevoix impact crater of probable Devonian age, whereas the isotopic signature of fault-related quartz-calcite veins is consistent with faulting during the Late Jurassic-Early Cretaceous. Existing and new clay K-Ar and apatite fission tracks (FT) data are presented for the SLRS. K-Ar dating was performed on clay material <0,2µm-size fractions from fault gouges and breccias along the Montmorency Falls (MF) and St-Laurent (SL) faults. The results suggest a tectonic activity along the MF fault from ca. 465 to 445 Ma, whereas results from the SL fault are suggestive of Middle Ordovician (ca. 465 Ma) and Middle Devonian (ca. 390 Ma) faulting. Apatite FT ages are from transects in the Montréal, Québec city and Charlevoix areas. In the Montreal transect, the ages vary from 190 Ma to 175 Ma in the footwall of rift faults, and from 135 to 110 Ma in the Oka Intrusion and adjacent Grenvillian rocks, which is obviously related to Cretaceous magmatism. In the Québec city area, FT dating was performed on both Grenvillian and overlying Appalachian rocks. Except for an amphibolite of the MF fault yielding 120 Ma due to either local thermal heat-flow or fluid-assisted faulting, the FT ages vary from 155 and 135 Ma. Preliminary FT data from the footwall of the SL fault in the Charlevoix area yielded ages of ca. 200 Ma. FT age data need to be interpreted with caution until uncertainties due to paleo-heatflows or to unusual mineral compositions are resolved. They suggest, however, that rocks cooled through ca. 100oC in Jurassic to Early-Cretaceous times, possibly during reactivation of the SLRS, which would be consistent with far-field tectonic activity related to North-Atlantic rifting.
We can barely comprehend the violence meteorites can cause if they land anywhere near a major rift valley! The succeeding undulations and jolts could cause tremendous sudden changes!
Along the eastern segment of the Amazon Fault, a rift opened up at the start of the Paleozoic. Early Jurassic reactivation. The northeast-trending Pisco-Jurua Fault cuts across the continent from the Pacific to the Guyana-Surinam border. Mesozoic continuation of the North Atlantic Rift; its Guyanan end opened up as the North Atlantic Rift opened. The separation of North and South America caused northwestern South America to move southwest along the Pisco-Jurua Fault, creating the Tacutu Graben in the Guyanan Shield, the gently folded Jurua Zone across the Amazon Basin, and the Pisco-Abancay deflection in the Andes. Pliocene reactivation at the Pacific end of the fault sheared the subducted slab of the Nazca Plate and may have contributed to the formation of the Nazca Ridge.
That is, it formed at the very beginning of life on earth. Ever since then, it continues, a crack in the continent. Why hasn't it split it in two? I suppose, as South America rotates across this half of the planet, the pressure on the leading edge which built up the Andes, makes a nice backbone. The USA is split at a 90 degree angle to South America's rift which is west to east. The Mississippi is north to south.
The New Madrid Seismic Zone lies at the northern end of the embayment. It was the site of the large New Madrid Earthquakes of 1811 - 1812. The area is underlain by some anomalous geology. The Reelfoot Rift is an ancient failed continental rift which dates back to the Precambrian break-up of the supercontinent Rodinia. The relatively more recent opening of the Atlantic Ocean and Gulf of Mexico during late Paleozoic to early Mesozoic break-up of Pangea no doubt affected and may have partially re-activated the old rift.
Another very ancient rift that is still active and still puzzles us. Like the Amazon, it is above sea level most of the way though it does sag very close to sea level long before it reaches the Gulf of Mexico. Probably due to back-filling during the era of no plantlife and other eras of deposits of fine topsoil from Asia, for example, during the Ice Ages.
Surmising that all continents and subcontinents have a rift valley right down the center, I looked for them in Siberia and the subcontinent of India.
The Deccan Traps formed between 60 and 68 million years ago, at the end of the Cretaceous period. The bulk of the volcanic eruption occurred at the Western Ghats (near Mumbai) some 66 million years ago. This series of eruptions may have lasted fewer than 30,000 years in total. The gases released in the process may have played a role in the K-T extinction event, which included the extinction of the dinosaurs.
Before the Deccan Traps region was reduced to its current size by erosion and continental drift, it is estimated that the original area covered by the lava flows was as large as 1.5 million km², approximately half the size of modern India. The present volume of directly observable lava flows is estimated to be around 512,000 km³.
As I have blogged in the past, I have visited the various volcanic events along the length of the New Mexican Rio Grande rift valley. One of the most recent lava non-volcanic flows on the continent occured in New Mexico and the crack in the ground simply spewed out miles and miles of lava that filled this valley as far as the eye could see! This happened very quickly, animals had to run swiftly to avoid being destroyed.
It is interesting that the great Deccan Traps event coincided yet again with a large celestial object hitting the earth! Some people believe one struck near India, in the ocean. It is possible. What is probable is, the center of India was dropping and India was splitting apart when the cracks went very deep into the earth and instead of ocean rushing in, lava came pouring out in prodigious amounts, suddenly and with great force. And not in a small way but across the entire rift valley like a coat being unzippered.
The goal of this project is to kinematically image extension in the Rio Grande Rift in order to address the following question: What controls extension within "narrow" continental rifts and how is it related to lithospheric heterogeneity?
Additional questions addressed by this research include: Is deformation steady or episodic? Do the observed Quaternary faults and geodetic strain rates agree? How is strain spatially accommodated? Is the Rio Grande Rift widening and propagating northward? What is the mantle rheology, and how is the style of deformation influenced by strain rate? How does the potential rift propagation manifest itself in the Neogene rotation of the Colorado Plateau?
I would say, 'Yes, it is propagating northwards in fits and starts!' The fits are usually meteorite-driven and quess what! The most recent great meteor event is obviously Meteor Crater which is nearby! And in the same timeframe as some of the volcanic events in New Mexico.
The Great Rift system consists of a series of north-northwest-trending fractures, which extend 50 miles from the northern margin of the eastern Snake River Plain, southward to the Snake River. In 1968, the Great Rift was designated as a national landmark.
The system has been divided into four separate sets of fractures. These four sets from north to south include: (1) the Great Rift set which trends N. 35' W. and cuts across the Craters of the Moon National Monument; (2) the Open Crack rift set which trends N. 30' W. and apparently has not experienced extrusive activity; (3) the King's Bowl rift set which trends N. 10' W; and (4) the Wapi rift set which is believed to trend north-south, but is covered by the Wapi flow. The total rift system is 62 miles long and may be the longest known rift zone in the conterminous United States.
62 miles is short for a rift zone. Many are thousands of miles long. Defining rift zones is still an art and not a science, I think.
The entire western USA, pressed hard by the Pacific plate and other plates riding under the continent, has many rift zones. The only ones that will fill in with water will be the Californian and other coastal areas as the coasts move independently of the continent itself. These other rift valleys fill not with water but with LAVA.
The Siberian Traps (Russian: Сибирские траппы) form a large igneous province in Siberia. The massive eruptive event spans the Permian-Triassic boundary, about 251 to 250 million years ago, and was essentially coincident with the Permian-Triassic extinction event in what was one of the largest known volcanic events of the last 500 million years of Earth's geological history. The Siberian Traps are the largest known volcanic eruption ever to have occurred in the history of Earth. The term 'traps' is derived from the Swedish word for stairs (trappa, or sometimes trapp), referring to the step-like hills forming the landscape of the region.
When this rift valley collapsed and then opened up with giant cracks that were literally the Cracks of Doom, the massive lava flow, the biggest on earth, filled in the entire center of the Asian continental mass. This event coincided not incidentally with the destruction of 90% of the species on earth. Aside from utterly destroying all the living things in its huge path, we know from fossils associated with other much smaller events, even fast running mammals could not outrun the swiftly flowing lava.
Like the later lava events, a probable very large meteoroid struck where Antarctica, Australia and South America came together. If the Siberian rift valley was getting very deep and wide, it could have triggered a catastrophic lava belching event that lasted for a few thousand years, killing a tremendous number of animals in all ecosystems. Perhaps destroying most of the oxygen in the atmosphere!
So my point is, not only are all continents still breaking apart even as they shove parts ever higher with various mountain-building events, the disassembly of the mega-continents is still ongoing. The glue that is keeping the continents together is these gigantic lava flows that cover over and fill in, great rift zones.
So there is a 50% chance that the East African Rift Valley might end up like all these other lava-filled valleys. And this will, if it is big and it looks pretty big, be a very dangerous time for us if it happens.
We know these things happen with little warning. Humans have witnessed this happening in New Mexico, for example. The hot mudflow in Indonesia is a good reminder how these work.