Post by Dave on Jan 10, 2013 20:32:36 GMT -5
We have had several conversations about the origin of the Scotia Plate.
ponderingconfusion.proboards.com/index.cgi?board=planetoidpangea&action=display&thread=185
The Fluid Dynamics of Whole Earth Decompression Theory (FD-WEDT) claims that this large geological formation is evidence of the oozing Pacific Ocean Floor spilling over into, and on top of (subduction), the Indian Ocean Floor. If this is a correct assumption, it suggests that the oozing of the Pacific Ocean Floor was quite viscous and therefore flowed very easily and quickly. It also suggests that the rate of flow was enormous. Both consistent with Whole Earth Decompression Dynamics (WEDD).
Sheet lavas
Sheet lavas emerge from fissure systems forming flows commonly ranging between 10m and 30m in thickness. They flow out so fast that vast volumes of basalt are discharged over an enormous area. Featureless lava plateaus are formed. During the eruption of Roza, Oregon, 14 million years ago, 1500km3 of sheet lavas were produced in about a week. (http://www.cartage.org.lb /en/themes /sciences/Earthscience /Geology /volcanoes /hazards /Types%20of%20Lava%20Flows.htm)
17-12 million years ago (Miocene) -- During this period, unusual volcanoes, called basalt floods, erupted in eastern Washington and Oregon. These volcanoes were cracks in the earth's crust, several miles long, which poured out floods of liquid molten rock. 41,000 cubic miles (170,000 cubic kilometers) of this lava spread to cover large parts of Oregon and Washington. Out of 270 lava flows that spread across the region, 21 poured through the Gorge (Columbia River Gorge) forming layers of rock up to 2,000 feet (600 meters) deep. (From: U.S. Army Corps of Engineers, Portland District, and the U.S. Department of the Interior, U.S. Geological Survey, The Geologic History of the Columbia River Gorge: Information Broshure)
From: en.wikipedia.org/wiki/Plateau_basalt
A flood basalt or trap basalt is the result of a giant volcanic eruption or series of eruptions that coats large stretches of land or the ocean floor with basalt lava. Flood basalts have occurred on continental scales (large igneous provinces) in prehistory, creating great plateaus and mountain ranges. Flood basalts have erupted at random intervals throughout geological history and are clear evidence that the Earth undergoes periods of enhanced activity rather than being in a uniform steady state.
The Deccan Traps of central India, the Siberian Traps, and the Columbia River Plateau of western North America are three regions covered by prehistoric flood basalts. The two largest flood basalt events in historic time have been at Eldgjá and Lakagigar, both in Iceland. The largest and best-preserved continental flood basalt terrain on Earth is part of the Mackenzie Large Igneous Province in Canada.
The surface covered by one eruption can vary from around 200,000 km² (Karoo) to 1,500,000 km² (Siberian Traps). The thickness can vary from 2000 meters (Deccan Traps) to 12,000 m (Lake Superior). These are smaller than the original volumes due to erosion.
The maria on the Moon, (as in the Sea of Tranquility,) are even more extensive, flood basalts.
en.wikipedia.org/wiki/Siberian_Traps
The Siberian Traps (Russian: Сибирские траппы, Sibirskije trappy) form a large region of volcanic rock, known as a large igneous province, in the Russian region of Siberia. The massive eruptive event which formed the traps, one of the largest known volcanic events of the last 500 million years of Earth's geological history, continued for a million years and spanned the Permian–Triassic boundary, about 251 million to 250 million years ago.
Vast volumes of basaltic lava paved over a large expanse of primeval Siberia in a flood basalt event. Today the area covered is about 2 million km2—roughly equal to western Europe in land area—and estimates of the original coverage are as high as 7 million km2. The original volume of lava is estimated to range from 1 million to 4 million km3.
en.wikipedia.org/wiki/Komatiite
Komatiite is a type of ultramafic mantle-derived volcanic rock. Komatiites have low silicon, potassium and aluminium, and high to extremely high magnesium content. Komatiite was named for its type locality along the Komati River in South Africa.
True komatiites are very rare and essentially restricted to rocks of Archaean age, with few Proterozoic or Phanerozoic komatiites known (although high-magnesian lamprophyres are known from the Mesozoic). This restriction in age is thought to be due to cooling of the mantle, which may have been up to 500 °C hotter during the early to middle Archaean. The early Earth had much higher heat production, due to the residual heat from planetary accretion, as well as the greater abundance of radioactive elements.
Morphology and occurrence
Komatiites often show pillow lava structure, autobrecciated upper margins consistent with underwater eruption forming a rigid upper skin to the lava flows, under which considerable lava tubes and pools accumulate. Proximal volcanic facies are thinner and interleaved with sulfidic sediments, black shales, cherts and tholeiitic basalts. Komatiites were produced from a relatively wet mantle. Evidence of this is from their association with felsics, occurrences of komatiitic tuffs, Niobium anomalies and by S- and H2O-borne rich mineralizations.
From: www2.ess.ucla.edu/~jewitt/class/Surfaces_Papers/Griffith_00.pdf
Ancient eruptions of even hotter and less viscous lavas called komatiites [generally thought to originate from hotspots in the Archaean and proterozoic eras, . 22109 years ago (e.g. Huppert et al 1984, Williams et al 1998)], and enormous outpourings of flood basalts, which flowed
hundreds of kilometers (e.g. see review by Cashman et al 1998) and generated large plateaus on both continents and ocean floors, have been preserved in regions of the Earth’s crust. These testify to flows much faster and more turbulent than any historically recorded.
Origin of the oceans' largest plateau
Science News, Vol. 133, No 26, June 25 1988,
www.questia.com/library/1G1-6831919/origin-of-the-oceans-largest-plateau
A 2,300-kilometer-long mystery known as the Kerguelen plateau stretches across the southern Indian Ocean near Antarctica. This structure, the world's largest submerged plateau, has long invited speculation and debate concerning its origins. … Because of the plateau's large size, some geoscientists thought it might be a fragment of Antarctica that splintered off when the Indian Ocean began to form.
From: en.wikipedia.org/wiki/Plateau_basalt
One proposed explanation for flood basalts is that they are caused by the combination of continental rifting and its associated decompression melting, in conjunction with a mantle plume also undergoing decompression melting, producing vast quantities of a tholeiitic basaltic magma. These have a very low viscosity, which is why they 'flood' rather than form taller volcanoes. Another explanation is that they result from the release, over a short time period, of melt that has accumulated in the mantle over a long time period.
en.wikipedia.org/wiki/Komatiite
The source of the Siberian Traps basalt has variously been attributed to a mantle plume which impacted the base of the earth's crust and erupted through the Siberian Craton, or to processes related to plate tectonics. Another possible cause may be the impact that formed the Wilkes Land crater, which may have been contemporaneous and would have been antipodal to the Traps. This controversial scientific debate is ongoing.
en.wikipedia.org/wiki/Large_igneous_province
Meteorite-induced formation
Seven pairs of hotspots and LIPs located on opposite sides of the earth have been noted; analyses indicate this coincident antipodal location is highly unlikely to be random. The hotspot pairs include a large igneous province with continental volcanism opposite an oceanic hotspot. Oceanic impacts of large meteorites are expected to have high efficiency in converting energy into seismic waves. These waves would propagate around the world and reconverge close to the antipodal position; small variations are expected as the seismic velocity varies depending upon the route characteristics along which the waves propagate. As the waves focus on the antipodal position, they put the crust at the focal point under significant stress and are proposed to rupture it, creating antipodal pairs. When the meteorite impacts a continent, the lower efficiency of kinetic energy conversion into seismic energy is not expected to create an antipodal hotspot.[12]
Dave’s Summary
They flow out so fast that vast volumes of basalt are discharged over an enormous area
Flood basalts have occurred on continental scales (large igneous provinces) in prehistory, creating great plateaus and mountain ranges.
On a continental scale! Prehistory!
Flood basalts are clear evidence that the Earth undergoes periods of enhanced activity rather than being in a uniform steady state.
… enormous outpourings of flood basalts, … generated large plateaus on both continents and ocean floors, have been preserved in regions of the Earth’s crust. These testify to flows much faster and more turbulent than any historically recorded.
Earth is not in a steady state – but undergoes periods of enhanced activity. Isn’t this a quite way to say that sometimes each under goes a catastrophic change rather than the millions of years of slow gradual change?
Vast volumes of basaltic lava paved over a large expanse of primeval Siberia in a flood basalt event. Today the area covered is about 2 million km2—roughly equal to western Europe in land area—and estimates of the original coverage are as high as 7 million km2. The original volume of lava is estimated to range from 1 million to 4 million km3.
1 to 4 Million cubic kilometers of volcanic outpouring - I heard someone say in a speech once, that this is enough volume to cover the entire planet in a layer of lava 10 feet thick.
… the mantle, which may have been up to 500 °C hotter during the early to middle Archaean. The early Earth had much higher heat production, due to the residual heat from planetary accretion, as well as the greater abundance of radioactive elements.
Heat generated by Whole Earth Decompression Dynamics! “… greater abundance of radioactive elements… “ - ? – Where did they all go? Just decayed away? -- Or lost by another mechanism.
The source of the Siberian Traps basalt has variously been attributed to a mantle plume which impacted the base of the earth's crust and erupted through the Siberian Craton, or to processes related to plate tectonics
Mantle Plume – let’s see – that would be molten mantle pushing upwards – that is exactly what WEDD and FD-WEDT claim.
Once Protoplanet Pangea lost its atmosphere
The planetoid fractured into its separate tectonic plates
Mantle Plumes spewed forth amazing amounts of sheet lavas
As the oceans separated from their mid-oceanic ridges – these sheet lavas formed the ocean floors – spewed forth from many decompression cracks around the world.
One surviving sheet lava from Siberia spewed forth possibly as much as 4 million cubic kilometers of materials – yet this would be very small indeed compared to the Pacific Ocean Floor basin.
ponderingconfusion.proboards.com/index.cgi?board=planetoidpangea&action=display&thread=185
The Fluid Dynamics of Whole Earth Decompression Theory (FD-WEDT) claims that this large geological formation is evidence of the oozing Pacific Ocean Floor spilling over into, and on top of (subduction), the Indian Ocean Floor. If this is a correct assumption, it suggests that the oozing of the Pacific Ocean Floor was quite viscous and therefore flowed very easily and quickly. It also suggests that the rate of flow was enormous. Both consistent with Whole Earth Decompression Dynamics (WEDD).
Sheet lavas
Sheet lavas emerge from fissure systems forming flows commonly ranging between 10m and 30m in thickness. They flow out so fast that vast volumes of basalt are discharged over an enormous area. Featureless lava plateaus are formed. During the eruption of Roza, Oregon, 14 million years ago, 1500km3 of sheet lavas were produced in about a week. (http://www.cartage.org.lb /en/themes /sciences/Earthscience /Geology /volcanoes /hazards /Types%20of%20Lava%20Flows.htm)
17-12 million years ago (Miocene) -- During this period, unusual volcanoes, called basalt floods, erupted in eastern Washington and Oregon. These volcanoes were cracks in the earth's crust, several miles long, which poured out floods of liquid molten rock. 41,000 cubic miles (170,000 cubic kilometers) of this lava spread to cover large parts of Oregon and Washington. Out of 270 lava flows that spread across the region, 21 poured through the Gorge (Columbia River Gorge) forming layers of rock up to 2,000 feet (600 meters) deep. (From: U.S. Army Corps of Engineers, Portland District, and the U.S. Department of the Interior, U.S. Geological Survey, The Geologic History of the Columbia River Gorge: Information Broshure)
From: en.wikipedia.org/wiki/Plateau_basalt
A flood basalt or trap basalt is the result of a giant volcanic eruption or series of eruptions that coats large stretches of land or the ocean floor with basalt lava. Flood basalts have occurred on continental scales (large igneous provinces) in prehistory, creating great plateaus and mountain ranges. Flood basalts have erupted at random intervals throughout geological history and are clear evidence that the Earth undergoes periods of enhanced activity rather than being in a uniform steady state.
The Deccan Traps of central India, the Siberian Traps, and the Columbia River Plateau of western North America are three regions covered by prehistoric flood basalts. The two largest flood basalt events in historic time have been at Eldgjá and Lakagigar, both in Iceland. The largest and best-preserved continental flood basalt terrain on Earth is part of the Mackenzie Large Igneous Province in Canada.
The surface covered by one eruption can vary from around 200,000 km² (Karoo) to 1,500,000 km² (Siberian Traps). The thickness can vary from 2000 meters (Deccan Traps) to 12,000 m (Lake Superior). These are smaller than the original volumes due to erosion.
The maria on the Moon, (as in the Sea of Tranquility,) are even more extensive, flood basalts.
en.wikipedia.org/wiki/Siberian_Traps
The Siberian Traps (Russian: Сибирские траппы, Sibirskije trappy) form a large region of volcanic rock, known as a large igneous province, in the Russian region of Siberia. The massive eruptive event which formed the traps, one of the largest known volcanic events of the last 500 million years of Earth's geological history, continued for a million years and spanned the Permian–Triassic boundary, about 251 million to 250 million years ago.
Vast volumes of basaltic lava paved over a large expanse of primeval Siberia in a flood basalt event. Today the area covered is about 2 million km2—roughly equal to western Europe in land area—and estimates of the original coverage are as high as 7 million km2. The original volume of lava is estimated to range from 1 million to 4 million km3.
en.wikipedia.org/wiki/Komatiite
Komatiite is a type of ultramafic mantle-derived volcanic rock. Komatiites have low silicon, potassium and aluminium, and high to extremely high magnesium content. Komatiite was named for its type locality along the Komati River in South Africa.
True komatiites are very rare and essentially restricted to rocks of Archaean age, with few Proterozoic or Phanerozoic komatiites known (although high-magnesian lamprophyres are known from the Mesozoic). This restriction in age is thought to be due to cooling of the mantle, which may have been up to 500 °C hotter during the early to middle Archaean. The early Earth had much higher heat production, due to the residual heat from planetary accretion, as well as the greater abundance of radioactive elements.
Morphology and occurrence
Komatiites often show pillow lava structure, autobrecciated upper margins consistent with underwater eruption forming a rigid upper skin to the lava flows, under which considerable lava tubes and pools accumulate. Proximal volcanic facies are thinner and interleaved with sulfidic sediments, black shales, cherts and tholeiitic basalts. Komatiites were produced from a relatively wet mantle. Evidence of this is from their association with felsics, occurrences of komatiitic tuffs, Niobium anomalies and by S- and H2O-borne rich mineralizations.
From: www2.ess.ucla.edu/~jewitt/class/Surfaces_Papers/Griffith_00.pdf
Ancient eruptions of even hotter and less viscous lavas called komatiites [generally thought to originate from hotspots in the Archaean and proterozoic eras, . 22109 years ago (e.g. Huppert et al 1984, Williams et al 1998)], and enormous outpourings of flood basalts, which flowed
hundreds of kilometers (e.g. see review by Cashman et al 1998) and generated large plateaus on both continents and ocean floors, have been preserved in regions of the Earth’s crust. These testify to flows much faster and more turbulent than any historically recorded.
Origin of the oceans' largest plateau
Science News, Vol. 133, No 26, June 25 1988,
www.questia.com/library/1G1-6831919/origin-of-the-oceans-largest-plateau
A 2,300-kilometer-long mystery known as the Kerguelen plateau stretches across the southern Indian Ocean near Antarctica. This structure, the world's largest submerged plateau, has long invited speculation and debate concerning its origins. … Because of the plateau's large size, some geoscientists thought it might be a fragment of Antarctica that splintered off when the Indian Ocean began to form.
From: en.wikipedia.org/wiki/Plateau_basalt
One proposed explanation for flood basalts is that they are caused by the combination of continental rifting and its associated decompression melting, in conjunction with a mantle plume also undergoing decompression melting, producing vast quantities of a tholeiitic basaltic magma. These have a very low viscosity, which is why they 'flood' rather than form taller volcanoes. Another explanation is that they result from the release, over a short time period, of melt that has accumulated in the mantle over a long time period.
en.wikipedia.org/wiki/Komatiite
The source of the Siberian Traps basalt has variously been attributed to a mantle plume which impacted the base of the earth's crust and erupted through the Siberian Craton, or to processes related to plate tectonics. Another possible cause may be the impact that formed the Wilkes Land crater, which may have been contemporaneous and would have been antipodal to the Traps. This controversial scientific debate is ongoing.
en.wikipedia.org/wiki/Large_igneous_province
Meteorite-induced formation
Seven pairs of hotspots and LIPs located on opposite sides of the earth have been noted; analyses indicate this coincident antipodal location is highly unlikely to be random. The hotspot pairs include a large igneous province with continental volcanism opposite an oceanic hotspot. Oceanic impacts of large meteorites are expected to have high efficiency in converting energy into seismic waves. These waves would propagate around the world and reconverge close to the antipodal position; small variations are expected as the seismic velocity varies depending upon the route characteristics along which the waves propagate. As the waves focus on the antipodal position, they put the crust at the focal point under significant stress and are proposed to rupture it, creating antipodal pairs. When the meteorite impacts a continent, the lower efficiency of kinetic energy conversion into seismic energy is not expected to create an antipodal hotspot.[12]
Dave’s Summary
They flow out so fast that vast volumes of basalt are discharged over an enormous area
Flood basalts have occurred on continental scales (large igneous provinces) in prehistory, creating great plateaus and mountain ranges.
On a continental scale! Prehistory!
Flood basalts are clear evidence that the Earth undergoes periods of enhanced activity rather than being in a uniform steady state.
… enormous outpourings of flood basalts, … generated large plateaus on both continents and ocean floors, have been preserved in regions of the Earth’s crust. These testify to flows much faster and more turbulent than any historically recorded.
Earth is not in a steady state – but undergoes periods of enhanced activity. Isn’t this a quite way to say that sometimes each under goes a catastrophic change rather than the millions of years of slow gradual change?
Vast volumes of basaltic lava paved over a large expanse of primeval Siberia in a flood basalt event. Today the area covered is about 2 million km2—roughly equal to western Europe in land area—and estimates of the original coverage are as high as 7 million km2. The original volume of lava is estimated to range from 1 million to 4 million km3.
1 to 4 Million cubic kilometers of volcanic outpouring - I heard someone say in a speech once, that this is enough volume to cover the entire planet in a layer of lava 10 feet thick.
… the mantle, which may have been up to 500 °C hotter during the early to middle Archaean. The early Earth had much higher heat production, due to the residual heat from planetary accretion, as well as the greater abundance of radioactive elements.
Heat generated by Whole Earth Decompression Dynamics! “… greater abundance of radioactive elements… “ - ? – Where did they all go? Just decayed away? -- Or lost by another mechanism.
The source of the Siberian Traps basalt has variously been attributed to a mantle plume which impacted the base of the earth's crust and erupted through the Siberian Craton, or to processes related to plate tectonics
Mantle Plume – let’s see – that would be molten mantle pushing upwards – that is exactly what WEDD and FD-WEDT claim.
Once Protoplanet Pangea lost its atmosphere
The planetoid fractured into its separate tectonic plates
Mantle Plumes spewed forth amazing amounts of sheet lavas
As the oceans separated from their mid-oceanic ridges – these sheet lavas formed the ocean floors – spewed forth from many decompression cracks around the world.
One surviving sheet lava from Siberia spewed forth possibly as much as 4 million cubic kilometers of materials – yet this would be very small indeed compared to the Pacific Ocean Floor basin.