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SNOWBALL EARTH
SNOWBALL EARTH. In 1987, the Caltech biomagnetist and paleomagnetist Joe Kirschvink gave undergraduate Dawn Sumner a rock sample to study for her senior thesis. The sample, collected by UCLA paleontologist Bruce Runnegar, was a reddish, uncompacted, rhythmically laminated siltstone from the Elatina Formation, a late Neoproterozoic, glacialand
SNOWBALL EARTH
SNOWBALL EARTH. Any viable explanation for snowball events must also explain why they are rare. Extensive low-latitude glaciation occurred only near the beginning (2.45-2.22 Ga) and the end (0.73-0.58 Ga) of the Proterozoic eon (Fig. 12).SNOWBALL EARTH
Joe Kirschvink, a biomagnetist and paleomagnetist at the Caifornia Institute of Technology in Pasadena, USA, coined the name "snowball earth". He recognized its self-reversing character (building on earlier work by atmospheric scientists James Walker, Hal Marshall and Jim Kasting) and was the first to associate the runaway ice-albedo concept to a known geological event, the Marinoan glaciation.SNOWBALL EARTH
The Snowball Earth website examines the evidence and theory behind the snowball earth hypothesis, the idea that the globe was covered by ice for long periods roughly 2220, 710 and 636 million years ago.SNOWBALL EARTH
Sir Douglas Mawson, geologist and explorer, was born in Yorkshire, on 5 May 1882. He grew up and was educated in Rooty Hill, near Sydney, and studies mining engineering at the University of Sydney, graduating in 1902. His first scientific exploration was in 1903SNOWBALL EARTH
2.2: Meridional (pole-to-equator) variation in relative mean annual insolation for a planet with an orbital obliquity of 23.5 degrees (e.g., present Earth). 2.3: Average snowline elevations from the Arctic to the Antarctic along the American Cordillera at present (red line) and during the Last Glacial Maximum (blue line) approximately22,000
SNOWBALL EARTH
SNOWBALL EARTH. Isotopes are normally fractionated in direct proportion to the differences in their masses. For example, fractionations between 17 O and 16 O are most often half as large exactly as those between 18 O and 16 O. For this reason, 17 O/ 16 O ratios are rarely measured because 17 O is less abundant in nature than 18 O, the 18 O/ 16SNOWBALL EARTH
SNOWBALL EARTH. Cap carbonates are continuous layers of limestone (CaCO 3) and/or dolostone (Ca 0.55 Mg 0.45 CO 3) that sharply overlie Neoproterozoic glacial deposits, or sub-glacial erosion surfaces where the glacial deposits are absent. They are typically 3-30 m thick and occur on platforms, shelves and slopes world-wide, even in regions A NEOPROTEROZOIC SNOWBALL EARTH tropical platform, consistent with a snowball glaciation. We measured inorganic d13C values of car- bonate rocks that spanned the glacial interval from several sections (Fig. 2) (10, 11).In gen- SNOWBALL EARTHOVERVIEWQUESTIONSTEACHING SLIDESBIBLIOGRAPHYGEOCHRONOLOGYRESEARCH NEWS Two interesting symposia were held at the IGC in Oslo August 6-14, 2008: Stratigraphic Correlation of Neoproterozoic Strata and Neoproterozoic Ice Ages. There was a symposium "Breakup of Rodinia and Snowball Earth" at the Gondwana 13 conference held in Dali, western China, 14-21 September 2008.SNOWBALL EARTH
SNOWBALL EARTH. In 1987, the Caltech biomagnetist and paleomagnetist Joe Kirschvink gave undergraduate Dawn Sumner a rock sample to study for her senior thesis. The sample, collected by UCLA paleontologist Bruce Runnegar, was a reddish, uncompacted, rhythmically laminated siltstone from the Elatina Formation, a late Neoproterozoic, glacialand
SNOWBALL EARTH
SNOWBALL EARTH. Any viable explanation for snowball events must also explain why they are rare. Extensive low-latitude glaciation occurred only near the beginning (2.45-2.22 Ga) and the end (0.73-0.58 Ga) of the Proterozoic eon (Fig. 12).SNOWBALL EARTH
Joe Kirschvink, a biomagnetist and paleomagnetist at the Caifornia Institute of Technology in Pasadena, USA, coined the name "snowball earth". He recognized its self-reversing character (building on earlier work by atmospheric scientists James Walker, Hal Marshall and Jim Kasting) and was the first to associate the runaway ice-albedo concept to a known geological event, the Marinoan glaciation.SNOWBALL EARTH
The Snowball Earth website examines the evidence and theory behind the snowball earth hypothesis, the idea that the globe was covered by ice for long periods roughly 2220, 710 and 636 million years ago.SNOWBALL EARTH
Sir Douglas Mawson, geologist and explorer, was born in Yorkshire, on 5 May 1882. He grew up and was educated in Rooty Hill, near Sydney, and studies mining engineering at the University of Sydney, graduating in 1902. His first scientific exploration was in 1903SNOWBALL EARTH
2.2: Meridional (pole-to-equator) variation in relative mean annual insolation for a planet with an orbital obliquity of 23.5 degrees (e.g., present Earth). 2.3: Average snowline elevations from the Arctic to the Antarctic along the American Cordillera at present (red line) and during the Last Glacial Maximum (blue line) approximately22,000
SNOWBALL EARTH
SNOWBALL EARTH. Isotopes are normally fractionated in direct proportion to the differences in their masses. For example, fractionations between 17 O and 16 O are most often half as large exactly as those between 18 O and 16 O. For this reason, 17 O/ 16 O ratios are rarely measured because 17 O is less abundant in nature than 18 O, the 18 O/ 16SNOWBALL EARTH
SNOWBALL EARTH. Cap carbonates are continuous layers of limestone (CaCO 3) and/or dolostone (Ca 0.55 Mg 0.45 CO 3) that sharply overlie Neoproterozoic glacial deposits, or sub-glacial erosion surfaces where the glacial deposits are absent. They are typically 3-30 m thick and occur on platforms, shelves and slopes world-wide, even in regions A NEOPROTEROZOIC SNOWBALL EARTH tropical platform, consistent with a snowball glaciation. We measured inorganic d13C values of car- bonate rocks that spanned the glacial interval from several sections (Fig. 2) (10, 11).In gen-SNOWBALL EARTH
SNOWBALL EARTH. In 1987, the Caltech biomagnetist and paleomagnetist Joe Kirschvink gave undergraduate Dawn Sumner a rock sample to study for her senior thesis. The sample, collected by UCLA paleontologist Bruce Runnegar, was a reddish, uncompacted, rhythmically laminated siltstone from the Elatina Formation, a late Neoproterozoic, glacialand
SNOWBALL EARTH
The survival of photoautotrophy has inspired investigation of sea-ice dynamics in a snowball earth utilizing computational climate models. With mean surface temperatures of -50°C (-74°F), floating ice thickens rapidly to ~1.0 km and flows under its own weight towards the equator, where it is thinnest and where ice inflow is balanced bySNOWBALL EARTH
1.11: Present global distribution of Sturtian, Marinoan and Ediacaran glacial and glacial-marine deposits (left), and secular variation in the carbon isotopic composition (δ 13 C) of marine carbonates (right) from 860 to 490 Ma (modified after Halverson et al., 2005) and their relation to the three glacial epochs and early faunal diversification (after Knoll and Carroll, 1999).SNOWBALL EARTH
SNOWBALL EARTH. Possibly by a lowering of atmospheric greenhouse gases to near-present levels through tectonically-mediated rock weathering, when the Sun was considerably dimmer than present. Evidence points to a reduction in so-called "greenhouse" gases in the atmosphere, principally CO 2 (carbon dioxide) and CH 4 (methane).SNOWBALL EARTH
Kirschvink was not the first to wrestle with the low-latitude Elatina results. George Williams (1975, 1993, 2000) had long advocated a large (>54°) orbital obliquity, or tilt (the angle between the Earth's axes of rotation and orbit around the sun), to account for low-latitude glaciation in conjunction with inferred strong equatorial seasonality during the Elatina glaciation (Williams andSNOWBALL EARTH
Snowball Earth Conference, Ascona, Switzerland 16-21 July 2006. The Snowball Earth hypothesis is one of the most intriguing and controversial research topics in the geological sciences. The hypothesis aims to reconcile a range of observational data regarding Neoproterozoic successions, including the association of glacial andglacially
SNOWBALL EARTH
A number of objections have been raised against the snowball earth hypothesis, many of which have been more or less successfully rebutted. The global deposits are probably diachronous (not the same age everywhere) and are no more extensive than Phanerozoic (Cambrianto Recent, or
SNOWBALL EARTH
10.6: Simulations using an AGCM for 750 Ma with coupled sea-ice and ice-sheet dynamics (Donnadieu et al., 2003): (A) with 900 ppm 2, land-based ice sheets build up but the ocean remains open; (B) with 300 ppm CO 2, ocean is completely ice covered but land-based ice sheets continue to grow, covering most global land area by 400 kyr after snowball onset; (C) same as (B) showing basal temperatureSNOWBALL EARTH
Kirschvink (1992), building on concepts developed by the planetary atmosphere chemist James C.G. Walker and associates in the 1980’s, proposed that a “snowball earth” (his name) was self-reversing because of silicate-weathering feedback in the tectonically-driven carbon cycle. 8.3: Modeled increase in Solar luminosity over geologictime
CARBON CYCLE DYNAMICS FOR A NEOPROTEROZOIC CLIMATE MODEL J. W. Crowley vi List of Figures and Tables: Figure # Description Page 1 δ13C data for the Neoproterozoic era 1 2 The Rothman carbon cycle model 4 3 Oxygen solubility as a function of temperature and salinity SNOWBALL EARTHOVERVIEWQUESTIONSTEACHING SLIDESBIBLIOGRAPHYGEOCHRONOLOGYRESEARCH NEWS Two interesting symposia were held at the IGC in Oslo August 6-14, 2008: Stratigraphic Correlation of Neoproterozoic Strata and Neoproterozoic Ice Ages. There was a symposium "Breakup of Rodinia and Snowball Earth" at the Gondwana 13 conference held in Dali, western China, 14-21 September 2008.SNOWBALL EARTH
SNOWBALL EARTH. In 1987, the Caltech biomagnetist and paleomagnetist Joe Kirschvink gave undergraduate Dawn Sumner a rock sample to study for her senior thesis. The sample, collected by UCLA paleontologist Bruce Runnegar, was a reddish, uncompacted, rhythmically laminated siltstone from the Elatina Formation, a late Neoproterozoic, glacialand
SNOWBALL EARTH
SNOWBALL EARTH. Any viable explanation for snowball events must also explain why they are rare. Extensive low-latitude glaciation occurred only near the beginning (2.45-2.22 Ga) and the end (0.73-0.58 Ga) of the Proterozoic eon (Fig. 12).SNOWBALL EARTH
The Snowball Earth website examines the evidence and theory behind the snowball earth hypothesis, the idea that the globe was covered by ice for long periods roughly 2220, 710 and 636 million years ago.SNOWBALL EARTH
Sir Douglas Mawson, geologist and explorer, was born in Yorkshire, on 5 May 1882. He grew up and was educated in Rooty Hill, near Sydney, and studies mining engineering at the University of Sydney, graduating in 1902. His first scientific exploration was in 1903SNOWBALL EARTH
The Gaskiers glaciation (circa 580 Ma) in eastern Newfoundland (Canada) has been shown from precise U-Pb zircon dating of multiple volcanic ash layers to have lasted less than 1.0 million years (Bowring et al., 2003). Short-lived glaciation contradicts the "hard" snowball earth hypothesis, which predicts they last for millions ofyears.
SNOWBALL EARTH
SNOWBALL EARTH. Possibly by a lowering of atmospheric greenhouse gases to near-present levels through tectonically-mediated rock weathering, when the Sun was considerably dimmer than present. Evidence points to a reduction in so-called "greenhouse" gases in the atmosphere, principally CO 2 (carbon dioxide) and CH 4 (methane).SNOWBALL EARTH
SNOWBALL EARTH. Isotopes are normally fractionated in direct proportion to the differences in their masses. For example, fractionations between 17 O and 16 O are most often half as large exactly as those between 18 O and 16 O. For this reason, 17 O/ 16 O ratios are rarely measured because 17 O is less abundant in nature than 18 O, the 18 O/ 16SNOWBALL EARTH
SNOWBALL EARTH. Cap carbonates are continuous layers of limestone (CaCO 3) and/or dolostone (Ca 0.55 Mg 0.45 CO 3) that sharply overlie Neoproterozoic glacial deposits, or sub-glacial erosion surfaces where the glacial deposits are absent. They are typically 3-30 m thick and occur on platforms, shelves and slopes world-wide, even in regions A NEOPROTEROZOIC SNOWBALL EARTH tropical platform, consistent with a snowball glaciation. We measured inorganic d13C values of car- bonate rocks that spanned the glacial interval from several sections (Fig. 2) (10, 11).In gen- SNOWBALL EARTHOVERVIEWQUESTIONSTEACHING SLIDESBIBLIOGRAPHYGEOCHRONOLOGYRESEARCH NEWS Two interesting symposia were held at the IGC in Oslo August 6-14, 2008: Stratigraphic Correlation of Neoproterozoic Strata and Neoproterozoic Ice Ages. There was a symposium "Breakup of Rodinia and Snowball Earth" at the Gondwana 13 conference held in Dali, western China, 14-21 September 2008.SNOWBALL EARTH
SNOWBALL EARTH. In 1987, the Caltech biomagnetist and paleomagnetist Joe Kirschvink gave undergraduate Dawn Sumner a rock sample to study for her senior thesis. The sample, collected by UCLA paleontologist Bruce Runnegar, was a reddish, uncompacted, rhythmically laminated siltstone from the Elatina Formation, a late Neoproterozoic, glacialand
SNOWBALL EARTH
SNOWBALL EARTH. Any viable explanation for snowball events must also explain why they are rare. Extensive low-latitude glaciation occurred only near the beginning (2.45-2.22 Ga) and the end (0.73-0.58 Ga) of the Proterozoic eon (Fig. 12).SNOWBALL EARTH
The Snowball Earth website examines the evidence and theory behind the snowball earth hypothesis, the idea that the globe was covered by ice for long periods roughly 2220, 710 and 636 million years ago.SNOWBALL EARTH
Sir Douglas Mawson, geologist and explorer, was born in Yorkshire, on 5 May 1882. He grew up and was educated in Rooty Hill, near Sydney, and studies mining engineering at the University of Sydney, graduating in 1902. His first scientific exploration was in 1903SNOWBALL EARTH
The Gaskiers glaciation (circa 580 Ma) in eastern Newfoundland (Canada) has been shown from precise U-Pb zircon dating of multiple volcanic ash layers to have lasted less than 1.0 million years (Bowring et al., 2003). Short-lived glaciation contradicts the "hard" snowball earth hypothesis, which predicts they last for millions ofyears.
SNOWBALL EARTH
SNOWBALL EARTH. Possibly by a lowering of atmospheric greenhouse gases to near-present levels through tectonically-mediated rock weathering, when the Sun was considerably dimmer than present. Evidence points to a reduction in so-called "greenhouse" gases in the atmosphere, principally CO 2 (carbon dioxide) and CH 4 (methane).SNOWBALL EARTH
SNOWBALL EARTH. Isotopes are normally fractionated in direct proportion to the differences in their masses. For example, fractionations between 17 O and 16 O are most often half as large exactly as those between 18 O and 16 O. For this reason, 17 O/ 16 O ratios are rarely measured because 17 O is less abundant in nature than 18 O, the 18 O/ 16SNOWBALL EARTH
SNOWBALL EARTH. Cap carbonates are continuous layers of limestone (CaCO 3) and/or dolostone (Ca 0.55 Mg 0.45 CO 3) that sharply overlie Neoproterozoic glacial deposits, or sub-glacial erosion surfaces where the glacial deposits are absent. They are typically 3-30 m thick and occur on platforms, shelves and slopes world-wide, even in regions A NEOPROTEROZOIC SNOWBALL EARTH tropical platform, consistent with a snowball glaciation. We measured inorganic d13C values of car- bonate rocks that spanned the glacial interval from several sections (Fig. 2) (10, 11).In gen-SNOWBALL EARTH
SNOWBALL EARTH. In 1987, the Caltech biomagnetist and paleomagnetist Joe Kirschvink gave undergraduate Dawn Sumner a rock sample to study for her senior thesis. The sample, collected by UCLA paleontologist Bruce Runnegar, was a reddish, uncompacted, rhythmically laminated siltstone from the Elatina Formation, a late Neoproterozoic, glacialand
SNOWBALL EARTH
The survival of photoautotrophy has inspired investigation of sea-ice dynamics in a snowball earth utilizing computational climate models. With mean surface temperatures of -50°C (-74°F), floating ice thickens rapidly to ~1.0 km and flows under its own weight towards the equator, where it is thinnest and where ice inflow is balanced bySNOWBALL EARTH
Joe Kirschvink, a biomagnetist and paleomagnetist at the Caifornia Institute of Technology in Pasadena, USA, coined the name "snowball earth". He recognized its self-reversing character (building on earlier work by atmospheric scientists James Walker, Hal Marshall and Jim Kasting) and was the first to associate the runaway ice-albedo concept to a known geological event, the Marinoan glaciation.SNOWBALL EARTH
The case for snowball earths is based on different lines of evidence. The global distribution of Sturtian and Marinoan glacial deposits, and the broad synchroneity of the latter based on seawater carbon isotope anomalies consistently framing the glacial strata.; The association of glacial or glacial marine deposits with thick carbonate (limestone or dolostone) successions, which occurSNOWBALL EARTH
A number of objections have been raised against the snowball earth hypothesis, many of which have been more or less successfully rebutted. The global deposits are probably diachronous (not the same age everywhere) and are no more extensive than Phanerozoic (Cambrianto Recent, or
SNOWBALL EARTH
1.3: Paleogeographic extent of continental ice sheets and permanent sea ice over the last 800 million years. Red lines indicate major mass extinctions. 1.4: Snowball Earth episodes correlate broadly with major turning points in the chemical history of seawater and the evolutionof life.
SNOWBALL EARTH
SNOWBALL EARTH. The steadily increasing Solar luminosity and the present continental configuration conspire against it, but a large asteroidal or cometary impact could possibly trigger a snowball earth given the present cold ocean. This is a fair question given that the global climate has cooled dramatically over the last 50 million yearsand
SNOWBALL EARTH
Snowball seawater would be laden with nutrients due to hydrothermal activity and limited organic productivity (Kirschvink, 2000). Algal “blooms’ and enhanced organic burial associated with rapid sedimentation when snowball oceans were uncorked would have released oxygen to the atmosphere (Kirschvink et al., 2000; Walter et al.,2000). This
SNOWBALL EARTH
Kirschvink was not the first to wrestle with the low-latitude Elatina results. George Williams (1975, 1993, 2000) had long advocated a large (>54°) orbital obliquity, or tilt (the angle between the Earth's axes of rotation and orbit around the sun), to account for low-latitude glaciation in conjunction with inferred strong equatorial seasonality during the Elatina glaciation (Williams andSNOWBALL EARTH
7.8: Simulations using an AGCM for 750 Ma with coupled sea-ice and ice-sheet dynamics (Donnadieu et al., 2003): (A) with 900 ppm CO 2, land-based ice sheets build up but the ocean remains open; (B) with 300 ppm CO 2, ocean is completely ice covered but land-based ice sheets continue to grow, covering most global land area by 400 kyr after snowball onset; (C) same as (B) showing basal SNOWBALL EARTHOVERVIEWQUESTIONSTEACHING SLIDESBIBLIOGRAPHYGEOCHRONOLOGYRESEARCH NEWS Two interesting symposia were held at the IGC in Oslo August 6-14, 2008: Stratigraphic Correlation of Neoproterozoic Strata and Neoproterozoic Ice Ages. There was a symposium "Breakup of Rodinia and Snowball Earth" at the Gondwana 13 conference held in Dali, western China, 14-21 September 2008.SNOWBALL EARTH
The Snowball Earth website examines the evidence and theory behind the snowball earth hypothesis, the idea that the globe was covered by ice for long periods roughly 2220, 710 and 636 million years ago.SNOWBALL EARTH
SNOWBALL EARTH. Any viable explanation for snowball events must also explain why they are rare. Extensive low-latitude glaciation occurred only near the beginning (2.45-2.22 Ga) and the end (0.73-0.58 Ga) of the Proterozoic eon (Fig. 12).SNOWBALL EARTH
Joe Kirschvink, a biomagnetist and paleomagnetist at the Caifornia Institute of Technology in Pasadena, USA, coined the name "snowball earth". He recognized its self-reversing character (building on earlier work by atmospheric scientists James Walker, Hal Marshall and Jim Kasting) and was the first to associate the runaway ice-albedo concept to a known geological event, the Marinoan glaciation.SNOWBALL EARTH
Sir Douglas Mawson, geologist and explorer, was born in Yorkshire, on 5 May 1882. He grew up and was educated in Rooty Hill, near Sydney, and studies mining engineering at the University of Sydney, graduating in 1902. His first scientific exploration was in 1903SNOWBALL EARTH
2.2: Meridional (pole-to-equator) variation in relative mean annual insolation for a planet with an orbital obliquity of 23.5 degrees (e.g., present Earth). 2.3: Average snowline elevations from the Arctic to the Antarctic along the American Cordillera at present (red line) and during the Last Glacial Maximum (blue line) approximately22,000
SNOWBALL EARTH
The Gaskiers glaciation (circa 580 Ma) in eastern Newfoundland (Canada) has been shown from precise U-Pb zircon dating of multiple volcanic ash layers to have lasted less than 1.0 million years (Bowring et al., 2003). Short-lived glaciation contradicts the "hard" snowball earth hypothesis, which predicts they last for millions ofyears.
SNOWBALL EARTH
7.8: Simulations using an AGCM for 750 Ma with coupled sea-ice and ice-sheet dynamics (Donnadieu et al., 2003): (A) with 900 ppm CO 2, land-based ice sheets build up but the ocean remains open; (B) with 300 ppm CO 2, ocean is completely ice covered but land-based ice sheets continue to grow, covering most global land area by 400 kyr after snowball onset; (C) same as (B) showing basalSNOWBALL EARTH
Kirschvink (1992), building on concepts developed by the planetary atmosphere chemist James C.G. Walker and associates in the 1980’s, proposed that a “snowball earth” (his name) was self-reversing because of silicate-weathering feedback in the tectonically-driven carbon cycle. 8.3: Modeled increase in Solar luminosity over geologictime
A NEOPROTEROZOIC SNOWBALL EARTH tropical platform, consistent with a snowball glaciation. We measured inorganic d13C values of car- bonate rocks that spanned the glacial interval from several sections (Fig. 2) (10, 11).In gen- SNOWBALL EARTHOVERVIEWQUESTIONSTEACHING SLIDESBIBLIOGRAPHYGEOCHRONOLOGYRESEARCH NEWS Two interesting symposia were held at the IGC in Oslo August 6-14, 2008: Stratigraphic Correlation of Neoproterozoic Strata and Neoproterozoic Ice Ages. There was a symposium "Breakup of Rodinia and Snowball Earth" at the Gondwana 13 conference held in Dali, western China, 14-21 September 2008.SNOWBALL EARTH
The Snowball Earth website examines the evidence and theory behind the snowball earth hypothesis, the idea that the globe was covered by ice for long periods roughly 2220, 710 and 636 million years ago.SNOWBALL EARTH
SNOWBALL EARTH. Any viable explanation for snowball events must also explain why they are rare. Extensive low-latitude glaciation occurred only near the beginning (2.45-2.22 Ga) and the end (0.73-0.58 Ga) of the Proterozoic eon (Fig. 12).SNOWBALL EARTH
Joe Kirschvink, a biomagnetist and paleomagnetist at the Caifornia Institute of Technology in Pasadena, USA, coined the name "snowball earth". He recognized its self-reversing character (building on earlier work by atmospheric scientists James Walker, Hal Marshall and Jim Kasting) and was the first to associate the runaway ice-albedo concept to a known geological event, the Marinoan glaciation.SNOWBALL EARTH
Sir Douglas Mawson, geologist and explorer, was born in Yorkshire, on 5 May 1882. He grew up and was educated in Rooty Hill, near Sydney, and studies mining engineering at the University of Sydney, graduating in 1902. His first scientific exploration was in 1903SNOWBALL EARTH
2.2: Meridional (pole-to-equator) variation in relative mean annual insolation for a planet with an orbital obliquity of 23.5 degrees (e.g., present Earth). 2.3: Average snowline elevations from the Arctic to the Antarctic along the American Cordillera at present (red line) and during the Last Glacial Maximum (blue line) approximately22,000
SNOWBALL EARTH
The Gaskiers glaciation (circa 580 Ma) in eastern Newfoundland (Canada) has been shown from precise U-Pb zircon dating of multiple volcanic ash layers to have lasted less than 1.0 million years (Bowring et al., 2003). Short-lived glaciation contradicts the "hard" snowball earth hypothesis, which predicts they last for millions ofyears.
SNOWBALL EARTH
7.8: Simulations using an AGCM for 750 Ma with coupled sea-ice and ice-sheet dynamics (Donnadieu et al., 2003): (A) with 900 ppm CO 2, land-based ice sheets build up but the ocean remains open; (B) with 300 ppm CO 2, ocean is completely ice covered but land-based ice sheets continue to grow, covering most global land area by 400 kyr after snowball onset; (C) same as (B) showing basalSNOWBALL EARTH
Kirschvink (1992), building on concepts developed by the planetary atmosphere chemist James C.G. Walker and associates in the 1980’s, proposed that a “snowball earth” (his name) was self-reversing because of silicate-weathering feedback in the tectonically-driven carbon cycle. 8.3: Modeled increase in Solar luminosity over geologictime
A NEOPROTEROZOIC SNOWBALL EARTH tropical platform, consistent with a snowball glaciation. We measured inorganic d13C values of car- bonate rocks that spanned the glacial interval from several sections (Fig. 2) (10, 11).In gen-SNOWBALL EARTH
SNOWBALL EARTH. In 1987, the Caltech biomagnetist and paleomagnetist Joe Kirschvink gave undergraduate Dawn Sumner a rock sample to study for her senior thesis. The sample, collected by UCLA paleontologist Bruce Runnegar, was a reddish, uncompacted, rhythmically laminated siltstone from the Elatina Formation, a late Neoproterozoic, glacialand
SNOWBALL EARTH
The survival of photoautotrophy has inspired investigation of sea-ice dynamics in a snowball earth utilizing computational climate models. With mean surface temperatures of -50°C (-74°F), floating ice thickens rapidly to ~1.0 km and flows under its own weight towards the equator, where it is thinnest and where ice inflow is balanced bySNOWBALL EARTH
Journal of Geophysical Research 110, C07010, 10.1029/2004JC002525. Dave Pollard and Jim Kasting (Pennsylvania State University) simulated a snowball earth in which thin (54°) orbital obliquity, or tilt (the angle between the Earth's axes of rotation and orbit around the sun), to account for low-latitude glaciation in conjunction with inferred strong equatorial seasonality during the Elatina glaciation (Williamsand
SNOWBALL EARTH
The Snowball Earth website examines the evidence and theory behind the snowball earth hypothesis, the idea that the globe was covered by ice for long periods roughly 2220, 710 and 636 million years ago.SNOWBALL EARTH
SNOWBALL EARTH. Cap carbonates are continuous layers of limestone (CaCO 3) and/or dolostone (Ca 0.55 Mg 0.45 CO 3) that sharply overlie Neoproterozoic glacial deposits, or sub-glacial erosion surfaces where the glacial deposits are absent. They are typically 3-30 m thick and occur on platforms, shelves and slopes world-wide, even in regions SNOWBALL EARTHOVERVIEWQUESTIONSTEACHING SLIDESBIBLIOGRAPHYGEOCHRONOLOGYRESEARCH NEWS Two interesting symposia were held at the IGC in Oslo August 6-14, 2008: Stratigraphic Correlation of Neoproterozoic Strata and Neoproterozoic Ice Ages. There was a symposium "Breakup of Rodinia and Snowball Earth" at the Gondwana 13 conference held in Dali, western China, 14-21 September 2008.SNOWBALL EARTH
SNOWBALL EARTH. In 1987, the Caltech biomagnetist and paleomagnetist Joe Kirschvink gave undergraduate Dawn Sumner a rock sample to study for her senior thesis. The sample, collected by UCLA paleontologist Bruce Runnegar, was a reddish, uncompacted, rhythmically laminated siltstone from the Elatina Formation, a late Neoproterozoic, glacialand
SNOWBALL EARTHSNOWBALL EARTH ERASNOWBALL EARTH THEORYWHAT CAUSED SNOWBALL EARTHHOW DID SNOWBALL EARTH ENDWHAT IS SNOWBALL EARTHWHY DID SNOWBALL EARTH HAPPEN SNOWBALL EARTH. Any viable explanation for snowball events must also explain why they are rare. Extensive low-latitude glaciation occurred only near the beginning (2.45-2.22 Ga) and the end (0.73-0.58 Ga) of the Proterozoic eon (Fig. 12). SNOWBALL EARTHSNOWBALL EARTH ERASNOWBALL EARTH BOOKSNOWBALL EARTH DOCUMENTARYTWO SNOWBALL EARTHWHAT CAUSED SNOWBALL EARTHEVIDENCE FORSNOWBALL EARTH
Joe Kirschvink, a biomagnetist and paleomagnetist at the Caifornia Institute of Technology in Pasadena, USA, coined the name "snowball earth". He recognized its self-reversing character (building on earlier work by atmospheric scientists James Walker, Hal Marshall and Jim Kasting) and was the first to associate the runaway ice-albedo concept to a known geological event, the Marinoan glaciation.SNOWBALL EARTH
Sir Douglas Mawson, geologist and explorer, was born in Yorkshire, on 5 May 1882. He grew up and was educated in Rooty Hill, near Sydney, and studies mining engineering at the University of Sydney, graduating in 1902. His first scientific exploration was in 1903SNOWBALL EARTH
2.2: Meridional (pole-to-equator) variation in relative mean annual insolation for a planet with an orbital obliquity of 23.5 degrees (e.g., present Earth). 2.3: Average snowline elevations from the Arctic to the Antarctic along the American Cordillera at present (red line) and during the Last Glacial Maximum (blue line) approximately22,000
SNOWBALL EARTH
SNOWBALL EARTH. Possibly by a lowering of atmospheric greenhouse gases to near-present levels through tectonically-mediated rock weathering, when the Sun was considerably dimmer than present. Evidence points to a reduction in so-called "greenhouse" gases in the atmosphere, principally CO 2 (carbon dioxide) and CH 4 (methane).SNOWBALL EARTH
Kirschvink was not the first to wrestle with the low-latitude Elatina results. George Williams (1975, 1993, 2000) had long advocated a large (>54°) orbital obliquity, or tilt (the angle between the Earth's axes of rotation and orbit around the sun), to account for low-latitude glaciation in conjunction with inferred strong equatorial seasonality during the Elatina glaciation (Williams andSNOWBALL EARTH
The Snowball Earth website examines the evidence and theory behind the snowball earth hypothesis, the idea that the globe was covered by ice for long periods roughly 2220, 710 and 636 million years ago.SNOWBALL EARTH
SNOWBALL EARTH. Cap carbonates are continuous layers of limestone (CaCO 3) and/or dolostone (Ca 0.55 Mg 0.45 CO 3) that sharply overlie Neoproterozoic glacial deposits, or sub-glacial erosion surfaces where the glacial deposits are absent. They are typically 3-30 m thick and occur on platforms, shelves and slopes world-wide, even in regionsSNOWBALL EARTH
SNOWBALL EARTH. In 1987, the Caltech biomagnetist and paleomagnetist Joe Kirschvink gave undergraduate Dawn Sumner a rock sample to study for her senior thesis. The sample, collected by UCLA paleontologist Bruce Runnegar, was a reddish, uncompacted, rhythmically laminated siltstone from the Elatina Formation, a late Neoproterozoic, glacialand
SNOWBALL EARTH
The survival of photoautotrophy has inspired investigation of sea-ice dynamics in a snowball earth utilizing computational climate models. With mean surface temperatures of -50°C (-74°F), floating ice thickens rapidly to ~1.0 km and flows under its own weight towards the equator, where it is thinnest and where ice inflow is balanced bySNOWBALL EARTH
Snowball earth describes the coldest global climate imaginable - a planet covered by glacial ice from pole to pole. The global mean temperature would be about -50°C (-74°F) because most of the Sun's (Solar) radiation would be reflected back to space by the icy surface. [The fraction of radiation reflected is termed albedo (a) and itranges
SNOWBALL EARTH
Near the beginning and end of the Proterozoic Eon, circa 2220 Ma ("Makganyene"), circa 710 Ma ("Sturtian") and circa 640 Ma ("Marinoan"). The last snowball earth ended 635 million years ago (Ma), near the end of the Proterozoic Eon.For reference, the oldest bilaterian animal fossils (555 Ma in Arctic Russia) are 80 million years younger. This snowball earth is often referred to as "MarinoanSNOWBALL EARTH
SNOWBALL EARTH. This educational kit includes Neoproterozoic rock samples taken from Namibia, East Greenland, and Canada's Mackenzie Mountains. 20 samples encompassing the most compelling evidence in the Snowball Earth (including tillites and cap carbonates) debate have been compiled into one, easy-to-use, comprehensive educationalpackage.
SNOWBALL EARTH
Kirschvink was not the first to wrestle with the low-latitude Elatina results. George Williams (1975, 1993, 2000) had long advocated a large (>54°) orbital obliquity, or tilt (the angle between the Earth's axes of rotation and orbit around the sun), to account for low-latitude glaciation in conjunction with inferred strong equatorial seasonality during the Elatina glaciation (Williams andSNOWBALL EARTH
A number of objections have been raised against the snowball earth hypothesis, many of which have been more or less successfully rebutted. The global deposits are probably diachronous (not the same age everywhere) and are no more extensive than Phanerozoic (Cambrianto Recent, or
SNOWBALL EARTH
1.3: Paleogeographic extent of continental ice sheets and permanent sea ice over the last 800 million years. Red lines indicate major mass extinctions. 1.4: Snowball Earth episodes correlate broadly with major turning points in the chemical history of seawater and the evolutionof life.
SNOWBALL EARTH
The Snowball Earth website examines the evidence and theory behind the snowball earth hypothesis, the idea that the globe was covered by ice for long periods roughly 2220, 710 and 636 million years ago.SNOWBALL EARTH
Kirschvink (1992), building on concepts developed by the planetary atmosphere chemist James C.G. Walker and associates in the 1980’s, proposed that a “snowball earth” (his name) was self-reversing because of silicate-weathering feedback in the tectonically-driven carbon cycle. 8.3: Modeled increase in Solar luminosity over geologictime
Overview | Questions | Teaching Slides | Bibliography | Geochronology | Research News | Meetings| People
The posted B.Sc. thesis by John Crowley provides supplementary information referred to in _Brief Matter Arising: Snowball Prevention Questioned_, published in the December 18, 2008 issue of _Nature_. New paleo-_p_CO2 proxy confirms elevated greenhouse forcing during Marinoan snowball meltdown Two interesting symposia were held at the IGC in Oslo August 6-14, 2008: Stratigraphic Correlation of Neoproterozoic Strata and Neoproterozoic Ice Ages . There was a symposium "Breakup of Rodinia and Snowball Earth" at the Gondwana 13 conference held in Dali, western China, 14-21 September2008.
This web site contains a number of teaching slides available for your use. They are organized into a 13 week course. You can view thumbnails and download slides here.
Educational Rock sample suite for Snowball Earth now available. What is Snowball Earth?When were they?
What caused them?
Could there be another? How did life survive?How did they end?
What are cap carbonates?Evidence for them
Evidence against themWhose idea anyway?
Did they kick-start life? This web site was originally funded through research grants from the U.S. National Science Foundation (EAR - Geology & Paleontology Division) to Paul F. Hoffman, with additional funding from Harvard University. Site design, construction, maintainence, and additional financial support by R.S. Hildebrand. Contents Copyright © 2006-2020 and excerpt for an updated bibliography , original content is left as an historical record.Details
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