MAFIC DYKE SWARMS
Stevens Island - NE Arnhem Land, Northern Territory Australia - Google Earth Image
The Stevens Island formation has all the elements of a ‘man-made’ stone fish trap - except that it is upside-down – instead of a Horseshoe ‘Ʊ’ it is Omega ‘Ω’ shaped. It is therefore the result of natural processes.
The PastMasters Omega Proposition is that the lines of dark rock are Mafic Dykes - walls of solidified volcanic rock that filled cracks in the surface of the Earth and elsewhere. We are not claiming that Dyke Swarms explain every line of rocks everywhere nor that everything is known about these extraordinary processes. You will see that the classification is not yet settled – even the three basic forms lack definition & the American variant ‘Dike’ does not help. These volcanic leads concentrate minerals so are well known to prospecting geologists as well as volcanologists and geologists in general. This is our attempt to bring these phenomena into the public domain so that extraordinary claims may be tested empirically. To have lived on this planet & remained unaware of mother nature’s stretchmarks - would be a shame.
The PastMasters Omega Proposition is that the lines of dark rock are Mafic Dykes - walls of solidified volcanic rock that filled cracks in the surface of the Earth and elsewhere. We are not claiming that Dyke Swarms explain every line of rocks everywhere nor that everything is known about these extraordinary processes. You will see that the classification is not yet settled – even the three basic forms lack definition & the American variant ‘Dike’ does not help. These volcanic leads concentrate minerals so are well known to prospecting geologists as well as volcanologists and geologists in general. This is our attempt to bring these phenomena into the public domain so that extraordinary claims may be tested empirically. To have lived on this planet & remained unaware of mother nature’s stretchmarks - would be a shame.
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This page is an introduction to Mafic Dykes which are the result of volcanic activity. They range in size from seemingly isolated ribbons of rock through to Giant Radiating Swarms of which some 30 examples were recorded on Earth in 2011 – 16 on Mars and 118 Radiating Dyke Swarms on Venus (see Ernst et al below). In the intervening quarter of a century these numbers have grown significantly and now include the many hundreds of Mantle Plume Heads on Earth. The most recent Australian Dyke Swarm being discovered off Exmouth in WA. (see Magee & Jackson 2019 bottom of page)
Mafic Dykes Stevens Island. Google Earth
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Stevens Is. NT - The Omega Trap - Google Earth Image
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Stevens Island's Omega Trap is 47kms WSW of the 'Trap' in Australians Bay at the SE corner of Marchinbar Island (aka Great Wessel Island). The trap shape is exacerbated by the angular cut of the foreshore whereby a circular diversion, in an otherwise straight wall, appears magnified.
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Mafic Dyke Swarms
Today the Continent of Australia is resolutely non-volcanic - it was not always so - between 500mya and 2.7bya it was subjected to extensive volcanic activity both below ground and on the surface - which was subjected to burial and erosion. In the Top End we are fortunate to have a landscape in the Wessel Islands that provides glimpses of the process involved. Mission Beach at Elcho Island was a beach some 500mya - it was buried by some 8000ft (1.7 to 2.2km) of sandstone laid down in the familiar layers of silt brought down by massive rivers from an eroding mountain range to the NW. The majority of this soft sandstone has been eroded away - except where a layer of harder material, such as bauxite, consolidates the surface leaving a range of hills which the rising seas turn into a chain of islands. Where the islands are cut by the sea we are offered a near vertical section through the landscape which reveals the dark volcanic rock that has filled cracks in the Earth's crust as it has risen under pressure from the molten rock below. Rivers carve similar sections through the landscape down the deepest valleys to the coast and provide a useful cross-section.
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Dyke Swarms are vertical walls of rock that criss-cross through the Earth's crust. As volcanic activity pushes up the crust from below - the fractures fill with molten rock. Up to 2.2billion years of erosion, burial and erosion later - they appear in the landscape in three basic forms of Parallel, Radiating & Curving lines which are MaFic because they are dark - being volcanic rock, high in Magnesium [Ma] & Ferric Oxides - so magnetic.
How these features are formed is discussed in the papers at the foot of the web page. Parts of them are intelligible to laymen and contain diagrams which may be helpful once the basic idea has penetrated the brain's defences. It is counter-intuitive because the forces are pushing up from below to split the crust like a loaf of bread and fill the gaps with molten rock from the centre of the Earth. All this occurs over thousands of millions of years, with the results lying buried below your feet until exposed when the land surface is eroded by weathering or cut away by either the sea, a river or a bulldozer.
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The Kildonan Dyke Swarm - South Coast of the Isle of Arran - Off the west coast of Scotland - inside the Mull of Kintyre. Google Earth
By way of an introduction and acclimatisation - this page shows examples, from all over the planet, to demonstrate that it is a fundamental process which is now visible globally to us through Google Earth and especially visible upon beaches where the land is sectioned by the sea or where rivers excavate an inspection trench through the lowest parts of the landscape and reveal the dykes as narrow rock bars.
Dykes Felsite in Shale Le Pulec Jersey Geo Channel Islands
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Pan-African Damara Sequence Brandberg Cape Town University
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Faial Is. Portugal Google Earth
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Dyke Faial Is. Portugal - H. Sooslu image
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GARY HINCKS / SCIENCE PHOTO LIBRARY
Caption Igneous intrusion. Cut-away illustration of the features produced when rising magma (molten rock) intrudes into existing rock. Clockwise from upper right: a volcano, formed when magma erupts through a conduit to the surface as lava; a stock or basolith, formed when rising magma replaces or forces aside existing rock; ring dykes, concentric vertical intrusions which cut through existing rock layers; sills, intrusions which run between the existing layers; and radial dykes, another form of vertical intrusion which may run for hundreds of miles. At bottom is a magma chamber. |
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Great Dyke volcanic intrusion - Zimbabwe - Science Photo Library
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Great Dyke - Zimbabwe - NASA
NASA / GSFC / METI / JAPAN SPACE SYSTEMS / U.S.,JAPAN ASTER SCIENCE TEAM / SCIENCE PHOTO LIBRARY
Satellite image of part of the Great Dyke volcanic intrusion (down centre) in Zimbabwe. This intrusion is thought to be about 2.55 billion years old, and was created when molten lava filled and widened a fracture in the Earth's crust. It is over 500 kilometres long and has an average width of 10 kilometres. The area is rich in minerals, including platinum, chromium and gold. Image obtained by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite.
Satellite image of part of the Great Dyke volcanic intrusion (down centre) in Zimbabwe. This intrusion is thought to be about 2.55 billion years old, and was created when molten lava filled and widened a fracture in the Earth's crust. It is over 500 kilometres long and has an average width of 10 kilometres. The area is rich in minerals, including platinum, chromium and gold. Image obtained by the Advanced Spaceborne Thermal Emission and Reflection Radiometer (ASTER) on NASA's Terra satellite.
Alaskan Dyke S. Johnathan image Nat Geo
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Minette Dyke New Mexico USA
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E4170275 Dolerite Dyke Science Photo Library - S. Stammers Namib Desert Namibia
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Multiple Igneous Intrusion Phases Kosterhavet Sweden
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Igneous (dolerite) compound dyke -geograph.org.uk B. Bowyer - Isle of Arran Scotland
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Above Left image:- "Dolerite dyke in the Namib desert. A dyke is an intrusion of igneous rock between an existing layer of rock. Dolerite corresponds to basalt in its chemical composition but in contrast to basalt, which emerges on the surface as lava, the magma in dolerite dykes solidifies underground. Photographed on the Welwitschia Drive, Namib Desert, Namibia." Sinclair Stammers Science Photo Library
Laxford Bridge Steph Walker - Lewesian Gneisses & Scourie Dykes
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Image by Perros Guirec, Brittany, France. SciencePhotoLibrary
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'The cuttings excavated in the 1980s as part of the A838 road improvements between Laxford Bridge and Rhiconich, in NW Scotland, provide dramatic exposures of gneisses that give a glimpse of processes that operate in the middle continental crust during mountain building. The age of shear deformation at Laxford can be established by radiometric dating of the granitic intrusions. These have yielded ages of c 1855 million years. However, the grey gneisses are much older (2700-2800 million years). Collectively these outcrops chart the youngest part of the history of the Lewisian complex in NW Scotland while these rocks were still in the middle crust. Subsequently these units were uplifted to close to the earth’s surface so that they were overlain by the Torridonian strata – some 1.2 billion years ago. These outcrops are part of the NW Highlands Geopark.' Professor Rob Butler for The Geological Society
Hartashen - Namibia
Hartashen in Armenia - south of the Caucasus Mountains.
Hartashen - Megalithic Avenue - Google Earth
Hartashen Armenia - Google Earth
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Hartashen Armenia Twin Avenues - The Road to Carnac - Google Earth
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Hartashen Armenia - Google Earth
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Hartashen Armenia - Google Earth
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Hartashen NE Armenia - Google Earth
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Hartashen NE Armenia - Google Earth
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Hartashen NE Armenia - Google Earth
Hudson Bay - Canada
The Mackenzie Dyke swarm in the Northwest Territories of Canada is the world's largest - over 311 miles (500kms) wide and 1,864 miles (3,000kms) long.
SW Hudson Bay Canada Mechs 3 Types
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SW Hudson Bay Canada Mechs 3 Types
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Kildonan - Isle of Arran - Scotland
DSCF0865 - Wigton Physics
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DSCF0858 - Wigton Physics
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Kildonan - South Coast Isle of Arran - Google Earth
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Kildonan - South Coast Isle of Arran - Google Earth
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Kildonan - South Coast Isle of Arran - Google Earth
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Kildonan Isle of Arran with Actual Archaeology - Google Earth
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Ship Rock, New Mexico. USA
Google Earth has new features including Historical Imagery in the Primary Database. This is Ship Rock, Navajo Volcanic Province, New Mexico. The dykes are seen emanating from the volcanic plumes. Being harder than the surrounding rock they resist the ground weathering and so are left as narrow walls that arch out across the landscape like ancient battlements. If the sea had cut this buried landscape then the weathered top of the dykes would appear as the dark lines that are sometimes mistaken for stone fish traps. It would be a simple process to test such features by coring and X-ray fluorescence (XRF).
That is a Stop Sign - these are Street View images within the new Google Earth Historical Imagery.
Mafic Dykes radiate from the source as parallel lines which erode to avenues of single stones & may be mistaken for the works of Neolithic man.
South Alligator Floodplain - Closer to home
Looking West on the Kakadu Hwy to South Alligator R. Bridge NT - Mantle Plume - lava chamber at right.
Sth Alligator R. Mantle Plume - 5/2014
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Sth Alligator R. Mantle Plume - Dr. Karen Dempsey - late Wet 2015
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Sources & Resources
Papers:- Halls, 1982; Halls and Fahrig, 1987; Ernst and Baragar, 1992; Coffin and Eldholm, 1994, 2005; Wilson and Head, 2002; Bryan and Ernst, 2008; Ernst, 2014.
Earth, Venus & Mars
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The Exmouth Dyke Swarm - WA
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