Earth, Cradle of Life

From Dust to Life ◽

10.23943/princeton/9780691175706.003.0011 ◽

2017 ◽

Author(s):

John Chambers ◽

Jacqueline Mitton

Keyword(s):

Plate Tectonics ◽

Basaltic Rock ◽

Early Earth ◽

Crustal Recycling ◽

Earth’S Interior ◽

Earth's Interior ◽

The Waves ◽

Basaltic Crust

This chapter studies the composition of early Earth, which consisted of two layers: a dense iron-rich core at the center, surrounded by a thick rocky mantle. Gradually, Earth acquired a third layer, a thin basaltic crust on the floor of the ocean. In a few places, the basaltic rock became thick enough to poke up above the waves to form the first primitive continents. As the basalt cooled, it grew denser and eventually became heavier than the mantle below. This configuration was unstable, and in places, the heavy basaltic crust began to sink, or subduct, back into the mantle, where it eventually mixed with rocks deep in Earth's interior. As the basaltic crust subducted, it pulled neighboring material with it, making room for new crust to form and setting up the conditions necessary for plate tectonics—the process of crustal recycling that continues to operate on Earth today.

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Using paired teaching for earthquake education in schools

Geoscience Communication ◽

10.5194/gc-4-281-2021 ◽

2021 ◽

Vol 4 (2) ◽

pp. 281-295

Author(s):

Solmaz Mohadjer ◽

Sebastian G. Mutz ◽

Matthew Kemp ◽

Sophie J. Gill ◽

Anatoly Ischuk ◽

...

Keyword(s):

Plate Tectonics ◽

Seismic Energy ◽

Classroom Culture ◽

Mitigation Measures ◽

Plate Boundaries ◽

Earthquake Hazards ◽

The Difference ◽

Earth’S Interior ◽

The Impact ◽

Earth's Interior

Abstract. In this study, we have created 10 geoscience video lessons that follow the paired-teaching pedagogical approach. This method is used to supplement the standard school curriculum with video lessons, instructed by geoscientists from around the world, coupled with activities carried out under the guidance of classroom teachers. The video lessons introduce students to the scientific concepts behind earthquakes (e.g. the Earth's interior, plate tectonics, faulting, and seismic energy), earthquake hazards, and mitigation measures (e.g. liquefaction, structural, and non-structural earthquake hazards). These concepts are taught through hands-on learning, where students use everyday materials to build models to visualize basic Earth processes that produce earthquakes and explore the effects of different hazards. To evaluate the effectiveness of these virtual lessons, we tested our videos in school classrooms in Dushanbe (Tajikistan) and London (United Kingdom). Before and after the video implementations, students completed questionnaires that probed their knowledge on topics covered by each video, including the Earth's interior, tectonic plate boundaries, and non-structural hazards. Our assessment results indicate that, while the paired-teaching video lessons appear to enhance student knowledge and understanding of some concepts (e.g. Earth's interior, earthquake location forecasting, and non-structural hazards), they bring little change to their views on the causes of earthquakes and their relation to plate boundaries. In general, the difference between UK and Tajik students' level of knowledge prior to and after video testing is more significant than the difference between pre- and post-knowledge for each group. This could be due to several factors affecting curriculum testing (e.g. level of teachers' participation and classroom culture) and students' learning of content (e.g. pre-existing hazards knowledge and experience). To maximize the impact of school-based risk reduction education, curriculum developers must move beyond innovative content and pedagogical approaches, take classroom culture into consideration, and instil skills needed for participatory learning and discovery.

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Using paired teaching for earthquake education in schools

10.5194/gc-2020-43 ◽

2020 ◽

Author(s):

Solmaz Mohadjer ◽

Sebastian G. Mutz ◽

Matthew Kemp ◽

Sophie J. Gill ◽

Anatoly Ischuk ◽

...

Keyword(s):

Risk Reduction ◽

Plate Tectonics ◽

Classroom Culture ◽

Plate Boundaries ◽

Earthquake Hazards ◽

School Based ◽

The Difference ◽

Earth’S Interior ◽

The Impact ◽

Earth's Interior

Abstract. Lack of access to science-based natural hazards information impedes the effectiveness of school-based disaster risk reduction education. To address this challenge, we have created ten geoscience video lessons that follow the paired teaching pedagogical approach. This method is used to supplement the standard school curriculum with video lessons instructed by geoscientists from around the world coupled with activities carried out by local classroom teachers. The video lessons introduce students to the scientific concepts behind earthquakes (e.g., Earth's interior, plate tectonics, faulting, and seismic energy), earthquake hazards and mitigation measures (e.g., liquefaction, structural and non-structural earthquake hazards). These concepts are taught through hands-on learning where students use everyday materials to build models to visualize basic Earth processes that produce earthquakes, and explore the effects of different hazards. To evaluate the effectiveness of these virtual lessons, we tested our videos with school classrooms in Dushanbe (Tajikistan) and London (United Kingdom). Before and after video implementations, students completed questionnaires that probed their knowledge on topics covered by each video including the Earth's interior, tectonic plate boundaries, and non-structural hazards. Our assessment results indicate that while the paired teaching videos appear to enhance student views and understanding of some concepts (e.g., Earth's interior, earthquake location forecasting, and non-structural hazards), they bring little change to their views on causes of earthquakes and their relation to plate boundaries. In general, the difference between UK and Tajik students' level of knowledge prior to and after video testing is more significant than the difference between pre- and post-knowledge for each group. This could be due to several factors affecting curriculum testing (e.g., level of teachers' participation and suitable classroom culture) and students' learning of content (e.g., pre-existing hazards knowledge and experience). Taken together, to maximize the impact of school-based risk reduction education, curriculum developers must move beyond innovative content and pedagogical approaches, take classroom culture into consideration, and instil skills needed for participatory learning and discovery.

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Ancient helium and tungsten isotopic signatures preserved in mantle domains least modified by crustal recycling

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.2009663117 ◽

2020 ◽

Vol 117 (49) ◽

pp. 30993-31001

Author(s):

Matthew G. Jackson ◽

Janne Blichert-Toft ◽

Saemundur A. Halldórsson ◽

Andrea Mundl-Petermeier ◽

Michael Bizimis ◽

...

Keyword(s):

Isotopic Signature ◽

Geochemical Data ◽

Recycled Materials ◽

Isotopic Signatures ◽

Crustal Recycling ◽

Ocean Island Basalts ◽

Depleted Mantle ◽

History Of ◽

Earth’S Interior ◽

Earth's Interior

Rare high-3He/4He signatures in ocean island basalts (OIB) erupted at volcanic hotspots derive from deep-seated domains preserved in Earth’s interior. Only high-3He/4He OIB exhibit anomalous182W—an isotopic signature inherited during the earliest history of Earth—supporting an ancient origin of high3He/4He. However, it is not understood why some OIB host anomalous182W while others do not. We provide geochemical data for the highest-3He/4He lavas from Iceland (up to 42.9 times atmospheric) with anomalous182W and examine how Sr-Nd-Hf-Pb isotopic variations—useful for tracing subducted, recycled crust—relate to high3He/4He and anomalous182W. These data, together with data on global OIB, show that the highest-3He/4He and the largest-magnitude182W anomalies are found only in geochemically depleted mantle domains—with high143Nd/144Nd and low206Pb/204Pb—lacking strong signatures of recycled materials. In contrast, OIB with the strongest signatures associated with recycled materials have low3He/4He and lack anomalous182W. These observations provide important clues regarding the survival of the ancient He and W signatures in Earth’s mantle. We show that high-3He/4He mantle domains with anomalous182W have low W and4He concentrations compared to recycled materials and are therefore highly susceptible to being overprinted with low3He/4He and normal (not anomalous)182W characteristic of subducted crust. Thus, high3He/4He and anomalous182W are preserved exclusively in mantle domains least modified by recycled crust. This model places the long-term preservation of ancient high3He/4He and anomalous182W in the geodynamic context of crustal subduction and recycling and informs on survival of other early-formed heterogeneities in Earth’s interior.

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Distribution, cycling and impact of water in the Earth's interior

National Science Review ◽

10.1093/nsr/nwx130 ◽

2017 ◽

Vol 4 (6) ◽

pp. 879-891 ◽

Cited By ~ 11

Author(s):

Huaiwei Ni ◽

Yong-Fei Zheng ◽

Zhu Mao ◽

Qin Wang ◽

Ren-Xu Chen ◽

...

Keyword(s):

Deep Water ◽

Plate Tectonics ◽

Water Distribution ◽

Seismic Velocity ◽

Water Cycle ◽

Critical Role ◽

Water Reservoir ◽

Plate Motion ◽

Earth’S Interior ◽

Earth's Interior

Abstract The Earth's deep interior is a hidden water reservoir on a par with the hydrosphere that is crucial for keeping the Earth as a habitable planet. In particular, nominally anhydrous minerals (NAMs) in the silicate Earth host a significant amount of water by accommodating H point defects in their crystal lattices. Water distribution in the silicate Earth is highly heterogeneous, and the mantle transition zone may contain more water than the upper and lower mantles. Plate subduction transports surface water to various depths, with a series of hydrous minerals and NAMs serving as water carriers. Dehydration of the subducting slab produces liquid phases such as aqueous solutions and hydrous melts as a metasomatic agent of the mantle. Partial melting of the metasomatic mantle domains sparks off arc volcanism, which, along with the volcanism at mid-ocean ridges and hotspots, returns water to the surface and completes the deep water cycle. There appears to have been a steady balance between hydration and dehydration of the mantle at least since the Phanerozoic. Earth's water probably originates from a primordial portion that survived the Moon-forming giant impact, with later delivery by asteroids and comets. Water could play a critical role in initiating plate tectonics. In the modern Earth, the storage and cycling of water profoundly modulates a variety of properties and processes of the Earth's interior, with impacts on surface environments. Notable examples include the hydrolytic weakening effect on mantle convection and plate motion, influences on phase transitions (on the solidus of mantle peridotite in particular) and dehydration embrittlement triggering intermediate- to deep-focus earthquakes. Water can reduce seismic velocity and enhance electrical conductivity, providing remote sensing methods for water distribution in the Earth's interior. Many unresolved issues around the deep water cycle require an integrated approach and concerted efforts from multiple disciplines.

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