Paleontology of Earth's Mantle

Sleep, Norman H.; Bird, Dennis K.; Pope, E. C.

doi:10.1146/annurev-earth-092611-090602

Cited by 48 publications

(37 citation statements)

References 149 publications

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“…The formation of the solid carbonate minerals on the modern Earth is mostly mediated by microorganisms growing carbonate shells 46 , 73 rather than just by inorganic precipitation, although earlier in Earth history most of the carbonate precipitation was inorganic. 79 The carbonate shell material accumulates on the ocean fl oor fi rst as a soft carbonate mud, and later by gradual heating and compaction is turned into chalk and then limestone. Additional carbonate forms inorganically fi lling fractures within the volcanic oceanic crust.…”

Section: Planetary Carbon Cycle and Long-term Climate Changementioning

confidence: 99%

Sustainable carbon emissions: The geologic perspective

DePaolo

2015

MRS Energy & Sustainability

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Discussion of climate change usually focuses on the rise of Earth's global average surface temperature. Because of the variability in temperature-daily, weekly, seasonal, annual, decadal-and the seemingly small temperature rise 15 (about 1 °C) recorded so far, global surface temperature increase is diffi cult to appreciate for many people. 61 The more dramatic effects of warming-melting glaciers and sea ice-are happening in high latitude regions where few people live. The observed temperature increase is itself misleading; although seemingly modest, it is an underestimate of the effect, because the temperature will continue to rise based on the current greenhouse gas content of the atmosphere and the projected continued emissions. The temperature rise to date is only a fraction of that already programmed into the Earth system. 15 , 59 The root cause of climate change is what could be called "carbon cycle change." To change climate, the amount of carbon dioxide and other so-called greenhouse gases in the atmosphere needs to change. 7 , 61 , 67 , 71 To change the amount of CO 2 in the atmosphere, there must be a change in the way carbon is transferred among the various forms and places it exists in and on the Earth. The movement of carbon between storage "reservoirs" on the Earth, including the atmosphere, is complicated and still under investigation. 15 , 34 , 77 This study is an attempt to present a simplifi ed version of the carbon cycle, to place the current discussions of climate change in a geological perspective and provide an entry point for those wishing to ABSTRACT Current issues with carbon emissions need to be understood in terms of natural geologic processes that move carbon on the Earth. Comparison of modern emissions with the norms and extremes of natural processes emphasizes the enormity of the current challenge, and also the reason there are uncertainties about the future effects. Reaching sustainable emissions in the future can be viewed as a need to systematically reduce the carbon intensity of energy production.Achieving sustainable carbon emissions requires understanding of Earth's natural carbon cycles. Geologic processes move carbon in large quantities between Earth reservoirs, including in and out of the deeper reaches of the planet, and regulate Earth's surface temperature within a narrow range suitable for life for the past 3-4 billion years. There have been large changes in atmospheric CO 2 in the geologic past; the largest to offset changes in the brightness of the Sun. Atmospheric CO 2 has been much higher in the past, but not since humans evolved. Geologic processes act slowly, even during times in the geologic past regarded as examples of catastrophic climate change. In contrast, over the past 100 years, Earth's carbon cycles have undergone revolutionary change as a result of a greatly accelerated transfer of carbon from geologic storage to the atmosphere . Today, about 98% of the movement of carbon out of geologic reservoirs (coal-, oil-, and gas-bearing sedimentary rocks and l...

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Section: Planetary Carbon Cycle and Long-term Climate Changementioning

confidence: 99%

Sustainable carbon emissions: The geologic perspective

DePaolo

2015

MRS Energy & Sustainability

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“…The Earth scientist and the biologist have two parallel tasks following previous essays (Sleep andBird, 2007, 2008; Sleep et al, 2011Sleep et al, , 2012: appraisal of whether the proposed venue could reasonably exist on the ancient Earth and conversely assuming that putative molecular biological hypotheses are correct to infer conditions on the early Earth. Given the collective ignorance of ancient environments, these tasks proceed in parallel.…”

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confidence: 99%

Geological and Geochemical Constraints on the Origin and Evolution of Life

Sleep

2018

Astrobiology

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The traditional tree of life from molecular biology with last universal common ancestor (LUCA) branching into bacteria and archaea (though fuzzy) is likely formally valid enough to be a basis for discussion of geological processes on the early Earth. Biologists infer likely properties of nodal organisms within the tree and, hence, the environment they inhabited. Geologists both vet tenuous trees and putative origin of life scenarios for geological and ecological reasonability and conversely infer geological information from trees. The latter approach is valuable as geologists have only weakly constrained the time when the Earth became habitable and the later time when life actually existed to the long interval between ∼4.5 and ∼3.85 Ga where no intact surface rocks are known. With regard to vetting, origin and early evolution hypotheses from molecular biology have recently centered on serpentinite settings in marine and alternatively land settings that are exposed to ultraviolet sunlight. The existence of these niches on the Hadean Earth is virtually certain. With regard to inferring geological environment from genomics, nodes on the tree of life can arise from true bottlenecks implied by the marine serpentinite origin scenario and by asteroid impact. Innovation of a very useful trait through a threshold allows the successful organism to quickly become very abundant and later root a large clade. The origin of life itself, that is, the initial Darwinian ancestor, the bacterial and archaeal roots as free-living cellular organisms that independently escaped hydrothermal chimneys above marine serpentinite or alternatively from shallow pore-water environments on land, the Selabacteria root with anoxygenic photosynthesis, and the Terrabacteria root colonizing land are attractive examples that predate the geological record. Conversely, geological reasoning presents likely events for appraisal by biologists. Asteroid impacts may have produced bottlenecks by decimating life. Thermophile roots of bacteria and archaea as well as a thermophile LUCA are attractive.

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“…Geological evidence indicates that the widespread preservation of primary MIF-S isotopic signatures in sediments and hydrothermally altered crustal rocks ceased after oxygenation of the atmosphere at ∼2.4 Ga. Thus, detection of MIF-S signatures in young oceanic lavas provides a "time stamp and certification" (9) that the sulfur in these lavas was at Earth's surface some time before 2.4 Ga.…”

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confidence: 99%