Greg Hirth

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James Gregory "Greg" Hirth (born June 4, 1963) is an American geophysicist, specializing in tectonophysics. [1] [2] He is known for his experiments in rock deformation and his applications of rheology in development of models for tectonophysics. [3]

Contents

Biography

Greg Hirth as a boy and teenager enjoyed the outdoors in the woods of Ohio and the mountains of Colorado. [4] He graduated in 1985 with a B.S. in geological sciences from Indiana University. At Brown University, he graduated in geological sciences with a master's degree in 1987 and a Ph.D. in 1991. His Ph.D. thesis was supervised by Jan Tullis. For the academic year 1991–1992, Hirth was a postdoc in the department of geology and geophysics at the University of Minnesota. There his supervisor was David L. Kohlstedt. In the department of geology and geophysics of the Woods Hole Oceanographic Institution (WHOI), Hirth was a postdoc in 1993, an assistant scientist from 1994 to 1998, and an associate scientist from 1998 to 2007 (with tenure from 2001). In the department of Earth, environmental and planetary sciences of Brown University, he was from 2007 to 2009 an associate professor and was appointed in 2010 to a full professorship, which he currently holds. From 2015 to 2020 he chaired his department. He has held visiting positions at Caltech (fall 1999), France's University of Montpellier (spring 2007), and Rice University (spring 2011). [2]

From 1993 to 2007, Hirth was a part-time research affiliate at Massachusetts Institute of Technology (MIT), as a participant in collaborative efforts in geophysics by WHOI and MIT. For the WHOI/MIT Joint Program, he was the leader for field trips in 1994 to Basin and Range National Monument, in 2001 to Yellowstone National Park and Snake River Plain, and in 2003 to Mount St. Helens and Puget Sound. [2]

Hirth has done ophiolite fieldwork [5] in Oman, in Josephine County, Oregon, in Washington State's Cascade Mountains, in the region near Big Jim Mountain in the Chiwaukum Mountains, and in Trinity County, California. He has also done geological fieldwork in Central Australia (1993), [2] in the Talkeetna Arc (2000–2002), [6] [7] in Norway (2009), and in California's Mecca Hills (2021). Hirth was on three research cruises to the Southwest Indian Ridge. [2]

From 2013 to 2015 Hirth was the president of the Tectonophysics Section of the American Geophysical Union. From 1997 to 1999 he served on the editorial board of the journal Geology. He was an associate editor from 1999 to 2002 for the Journal of Geophysical Research and from 2006 to 2010 for the journal Geochemistry, Geophysics, Geosystems (colloquially called G-cubed). [2]

Hirth's 1996 paper Water in the oceanic upper mantle: Implications for rheology, melt extraction and the evolution of the lithosphere, co-authored with David L. Kohlstedt, [8] has been cited more than 1750 times. Hirth is the author or co-author of more than 25 articles that have been cite more than 100 time each. [3] He has done research on earthquakes, [9] [10] [11] [12] effects of melt and creep in the mantle on the rheology of the aggregate, [13] [14] [15] and the effects of grain size evolution on geophysical processes. [16] [17] [18] He and his colleagues have used experimental and theoretical rheology in constructing models of the oceanic lithosphere, [19] [20] the Iceland hotspot [21] and several other geophysical phenomena. [3]

Hirth was elected in 2006 a Fellow of the Mineralogical Society of America and in 2008 a Fellow of the American Geophysical Union (AGU). [2] He gave the AGU's Francis Birch Lecture in 2017. [22] He received the George P. Woollard Award from the Geological Society of America (GSA) in 2018. [3]

His father, John Price Hirth, was elected in 1974 a member of the National Academy of Engineering and in 1994 a member of the National Academy of Sciences. [23] [24] Greg Hirth married Ann E. Mulligan, whom he met at Brown University. [4] She graduated in 1988 from Brown University with an A.B. in geological sciences and in 1999 from the University of Connecticut with a Ph.D. in environmental engineering. She is a researcher employed at WHOI's Marine Policy Center. [25]

Selected publications

Articles

Books

Related Research Articles

<span class="mw-page-title-main">Lithosphere</span> Outermost shell of a terrestrial-type planet or natural satellite

A lithosphere is the rigid, outermost rocky shell of a terrestrial planet or natural satellite. On Earth, it is composed of the crust and the lithospheric mantle, the topmost portion of the upper mantle that behaves elastically on time scales of up to thousands of years or more. The crust and upper mantle are distinguished on the basis of chemistry and mineralogy.

<span class="mw-page-title-main">Asthenosphere</span> Highly viscous, mechanically weak, and ductile region of Earths mantle

The asthenosphere is the mechanically weak and ductile region of the upper mantle of Earth. It lies below the lithosphere, at a depth between ~80 and 200 km below the surface, and extends as deep as 700 km (430 mi). However, the lower boundary of the asthenosphere is not well defined.

<span class="mw-page-title-main">Subduction</span> A geological process at convergent tectonic plate boundaries where one plate moves under the other

Subduction is a geological process in which the oceanic lithosphere and some continental lithosphere is recycled into the Earth's mantle at convergent boundaries. Where the oceanic lithosphere of a tectonic plate converges with the less dense lithosphere of a second plate, the heavier plate dives beneath the second plate and sinks into the mantle. A region where this process occurs is known as a subduction zone, and its surface expression is known as an arc-trench complex. The process of subduction has created most of the Earth's continental crust. Rates of subduction are typically measured in centimeters per year, with rates of convergence as high as 11 cm/year.

<span class="mw-page-title-main">Post-glacial rebound</span> Rise of land masses after glacial period

Post-glacial rebound is the rise of land masses after the removal of the huge weight of ice sheets during the last glacial period, which had caused isostatic depression. Post-glacial rebound and isostatic depression are phases of glacial isostasy, the deformation of the Earth's crust in response to changes in ice mass distribution. The direct raising effects of post-glacial rebound are readily apparent in parts of Northern Eurasia, Northern America, Patagonia, and Antarctica. However, through the processes of ocean siphoning and continental levering, the effects of post-glacial rebound on sea level are felt globally far from the locations of current and former ice sheets.

Tectonophysics, a branch of geophysics, is the study of the physical processes that underlie tectonic deformation. This includes measurement or calculation of the stress- and strain fields on Earth’s surface and the rheologies of the crust, mantle, lithosphere and asthenosphere.

<span class="mw-page-title-main">Craton</span> Old and stable part of the continental lithosphere

A craton is an old and stable part of the continental lithosphere, which consists of Earth's two topmost layers, the crust and the uppermost mantle. Having often survived cycles of merging and rifting of continents, cratons are generally found in the interiors of tectonic plates; the exceptions occur where geologically recent rifting events have separated cratons and created passive margins along their edges. Cratons are characteristically composed of ancient crystalline basement rock, which may be covered by younger sedimentary rock. They have a thick crust and deep lithospheric roots that extend as much as several hundred kilometres into Earth's mantle.

<span class="mw-page-title-main">Continental crust</span> Layer of rock that forms the continents and continental shelves

Continental crust is the layer of igneous, metamorphic, and sedimentary rocks that forms the geological continents and the areas of shallow seabed close to their shores, known as continental shelves. This layer is sometimes called sial because its bulk composition is richer in aluminium silicates (Al-Si) and has a lower density compared to the oceanic crust, called sima which is richer in magnesium silicate (Mg-Si) minerals. Changes in seismic wave velocities have shown that at a certain depth, there is a reasonably sharp contrast between the more felsic upper continental crust and the lower continental crust, which is more mafic in character.

<span class="mw-page-title-main">Oceanic crust</span> Uppermost layer of the oceanic portion of a tectonic plate

Oceanic crust is the uppermost layer of the oceanic portion of the tectonic plates. It is composed of the upper oceanic crust, with pillow lavas and a dike complex, and the lower oceanic crust, composed of troctolite, gabbro and ultramafic cumulates. The crust overlies the rigid uppermost layer of the mantle. The crust and the rigid upper mantle layer together constitute oceanic lithosphere.

<span class="mw-page-title-main">Mid-ocean ridge</span> Basaltic underwater mountain system formed by plate tectonic spreading

A mid-ocean ridge (MOR) is a seafloor mountain system formed by plate tectonics. It typically has a depth of about 2,600 meters (8,500 ft) and rises about 2,000 meters (6,600 ft) above the deepest portion of an ocean basin. This feature is where seafloor spreading takes place along a divergent plate boundary. The rate of seafloor spreading determines the morphology of the crest of the mid-ocean ridge and its width in an ocean basin.

Carmen Gaina is the Director of the Centre for Earth Evolution and Dynamics (CEED) a Norwegian Centre of Excellence hosted at the Department of Geosciences, University of Oslo, Norway.

<span class="mw-page-title-main">Slab (geology)</span> The portion of a tectonic plate that is being subducted

In geology, the slab is a significant constituent of subduction zones.

<span class="mw-page-title-main">Crustal recycling</span> Tectonic recycling process

Crustal recycling is a tectonic process by which surface material from the lithosphere is recycled into the mantle by subduction erosion or delamination. The subducting slabs carry volatile compounds and water into the mantle, as well as crustal material with an isotopic signature different from that of primitive mantle. Identification of this crustal signature in mantle-derived rocks is proof of crustal recycling.

<span class="mw-page-title-main">Tessera (Venus)</span> Region of deformed terrain on Venus

A tessera is a region of heavily deformed terrain on Venus, characterized by two or more intersecting tectonic elements, high topography, and subsequent high radar backscatter. Tesserae often represent the oldest material at any given location and are among the most tectonically deformed terrains on Venus's surface. Diverse types of tessera terrain exist. It is not currently clear if this is due to a variety in the interactions of Venus's mantle with regional crustal or lithospheric stresses, or if these diverse terrains represent different locations in the timeline of crustal plateau formation and fall. Multiple models of tessera formation exist and further extensive studies of Venus's surface are necessary to fully understand this complex terrain.

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Stanley Robert Hart is an American geologist, geochemist, leading international expert on mantle isotope geochemistry, and pioneer of chemical geodynamics.

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References

  1. ↑ "Greg Hirth". Department of Earth, Environtal and Planetary Sciences (DEEPS), Brown University. (home page)
  2. 1 2 3 4 5 6 7 8 "Greg Hirth, Curriculum Vitae" (PDF). Brown University.
  3. 1 2 3 4 Forsyth, Donald. "2018 George P. Willard Award, Presented to Greg Hirth". The Geological Society of America.
  4. 1 2 "Greg Hirth". OCEANUS, The Journal of Our Ocean Planet. Woods Hole Oceanographic Institution.
  5. ↑ Kelemen, Peter B.; Braun, Michael; Hirth, Greg (2000). "Spatial distribution of melt conduits in the mantle beneath oceanic spreading ridges: Observations from the Ingalls and Oman ophiolites". Geochemistry, Geophysics, Geosystems. 1 (7): 1005. Bibcode:2000GGG.....1.1005K. doi: 10.1029/1999GC000012 . S2CID   128772321. (See list of ophiolites.)
  6. ↑ Mehl, Luc; Hacker, Bradley R.; Hirth, Greg; Kelemen, Peter B. (2003). "Arc‐parallel flow within the mantle wedge: Evidence from the accreted Talkeetna arc, south central Alaska". Journal of Geophysical Research: Solid Earth. 108 (B8): 2375. Bibcode:2003JGRB..108.2375M. doi:10.1029/2002JB002233.
  7. ↑ Keller, C. Brehnin (6 October 2023). "Talkeetna Arc, Alaska".
  8. ↑ Hirth, Greg; Kohlstedt, David L. (1996). "Water in the oceanic upper mantle: Implications for rheology, melt extraction and the evolution of the lithosphere". Earth and Planetary Science Letters. 144 (1–2): 93–108. Bibcode:1996E&PSL.144...93H. doi:10.1016/0012-821X(96)00154-9.
  9. ↑ Kelemen, Peter B.; Hirth, Greg (2007). "A periodic shear-heating mechanism for intermediate-depth earthquakes in the mantle". Nature. 446 (7137): 787–790. Bibcode:2007Natur.446..787K. doi:10.1038/nature05717. PMID   17429398. S2CID   4340739.
  10. ↑ Okazaki, Keishi; Hirth, Greg (2016). "Dehydration of lawsonite could directly trigger earthquakes in subducting oceanic crust". Nature. 530 (7588): 81–84. Bibcode:2016Natur.530...81O. doi:10.1038/nature16501. PMID   26842057. S2CID   4453183.
  11. ↑ Tsai, Victor C.; Hirth, Greg (2020). "Elastic Impact Consequences for High‐Frequency Earthquake Ground Motion". Geophysical Research Letters. 47 (5). Bibcode:2020GeoRL..4786302T. doi: 10.1029/2019GL086302 . S2CID   216314139.
  12. ↑ Tsai, Victor C.; Hirth, Greg; Trugman, Daniel T.; Chu, Shanna X. (2021). "Impact Versus Frictional Earthquake Models for High‐Frequency Radiation in Complex Fault Zones". Journal of Geophysical Research: Solid Earth. 126 (8). Bibcode:2021JGRB..12622313T. doi:10.1029/2021JB022313. S2CID   237723389.
  13. ↑ Hirth, Greg; Tullis, Jan (1994). "The brittle‐plastic transition in experimentally deformed quartz aggregates". Journal of Geophysical Research: Solid Earth. 99 (B6): 11731–11747. Bibcode:1994JGR....9911731H. doi:10.1029/93JB02873.
  14. ↑ Hirth, Greg; Kohlstedt, David L. (1995). "Experimental constraints on the dynamics of the partially molten upper mantle: Deformation in the diffusion creep regime". Journal of Geophysical Research: Solid Earth. 100 (B2): 1981–2001. Bibcode:1995JGR...100.1981H. doi: 10.1029/94JB02128 .
  15. ↑ Hirth, Greg; Kohlstedt, David L. (1995). "Experimental constraints on the dynamics of the partially molten upper mantle: 2. Deformation in the dislocation creep regime". Journal of Geophysical Research: Solid Earth. 100 (B8): 15441–15449. Bibcode:1995JGR...10015441H. doi:10.1029/95JB01292.
  16. ↑ Behn, Mark D.; Hirth, Greg; Elsenbeck Ii, James R. (2009). "Implications of grain size evolution on the seismic structure of the oceanic upper mantle". Earth and Planetary Science Letters. 282 (1–4): 178–189. Bibcode:2009E&PSL.282..178B. doi:10.1016/j.epsl.2009.03.014. hdl: 1912/2859 .
  17. ↑ Jaroslow, G.E.; Hirth, G.; Dick, H.J.B. (1996). "Abyssal peridotite mylonites: Implications for grain-size sensitive flow and strain localization in the oceanic lithosphere". Tectonophysics. 256 (1–4): 17–37. Bibcode:1996Tectp.256...17J. doi:10.1016/0040-1951(95)00163-8.
  18. ↑ Kidder, Steven; Hirth, Greg; Avouac, Jean-Philippe; Behr, Whitney (2016). "The influence of stress history on the grain size and microstructure of experimentally deformed quartzite". Journal of Structural Geology. 83: 194–206. Bibcode:2016JSG....83..194K. doi: 10.1016/j.jsg.2015.12.004 .
  19. ↑ Evans, R. L.; Lizarralde, D.; Collins, J.; Hirth, G.; Gaherty, J. "Structure of the Oceanic Mantle: Geophysical Constraints on Lithosphere Evolution" (PDF). DefLAB Workshop, Dublin Institute for Advanced Studies, June 2009 (invited). DefLAB
  20. ↑ Escartín, J.; Hirth, G.; Evans, B. (2001). "Strength of slightly serpentinized peridotites: Implications for the tectonics of oceanic lithosphere". Geology. 29 (11): 1023. Bibcode:2001Geo....29.1023E. doi:10.1130/0091-7613(2001)029<1023:SOSSPI>2.0.CO;2. ISSN   0091-7613.
  21. ↑ Ito, Garrett; Shen, Yang; Hirth, Greg; Wolfe, Cecily J. (1999). "Mantle flow, melting, and dehydration of the Iceland mantle plume". Earth and Planetary Science Letters. 165 (1): 81–96. Bibcode:1999E&PSL.165...81I. doi:10.1016/S0012-821X(98)00216-7.
  22. ↑ "2017 Fall Meeting - T34A: Birch Lecture". YouTube ; lecture by Greg Hirth on December 13, 2017{{cite web}}: CS1 maint: postscript (link)
  23. ↑ "Hirth, John Price, 1930-". American Institute of Physics (AIP).
  24. ↑ "John P. Hirth". Member Directory, National Academy of Sciences.
  25. ↑ "Ann Mulligan – WHOI People Directory". Woods Hole Oceanographic Institution.
  26. ↑ "Luc Mehl". Mountaineers Books.
  27. ↑ "An Interview with Luc Mehl". A.M.H. Fine Mountain Equipment since 1974.
  28. ↑ "Luc Mehl channel". YouTube .
  29. ↑ "Things To Luc At, Wilderness Safety & Alaskan Advencture".
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