Joseph Kirschvink

from Wikipedia, the free encyclopedia

Joseph L. Kirschvink , called Joe Kirschvink, (* 1953 ) is an American geologist, geophysicist and professor at the California Institute of Technology (Caltech), known for his contributions to paleomagnetism and biomagnetism (discovery of the first magnetofossils) and the hypothesis of the snowball Earth .

Life

Kirschvink studied at Caltech with a bachelor's and master's degree (the latter in 1975) and at Princeton University with an MA in 1978 and a doctorate in 1979. He became an Assistant Professor at Caltech in 1981, Associate Professor in 1987 and Professor in 1992. Since 2004 he has been Van Wingen Professor of Geobiology.

plant

Kirschvink was significantly involved in the development of various modern measuring techniques in paleomagnetism (2 G magnetometer, SQUID microscopy). He was a pioneer of biomagnetism in bacteria and discovered the first fossil remains of magnetic orientation of bacteria, whose magnetite crystals he identified as a source of paleomagnetism in sedimentary rocks.

In 1992 he proposed the hypothesis of the snowball earth , a global glaciation 2.4 billion years ago that was overcome again by greenhouse gases from volcanic activity. He sees the deposition of the strip ores as a result of the global icing at the time.

He is known for studying small magnetite crystals in rocks and living beings (biomineralization), from which he draws conclusions about their place of origin (paleomagnetism). Such investigations of magnetite crystals 2.4 billion year old glacier deposits in Australia (Elatina Formation), whose position he localized at the equator, also led him to the thesis of a global paleoproterozoic glaciation (Snowball Earth).

He also supports the thesis of the origin of life on Mars under desert-like conditions (salt lakes). According to Kirschvink, the early life forms came to earth via Martian meteorites. He examined numerous Martian meteorites and was also able to find signs of an earlier magnetic field (which also proved that within the meteorites, when they pass through the Earth's atmosphere, perfectly life-compatible conditions can prevail). He thinks that he has identified magnetic fossils (magnetite from fossil bacteria) in the Martian rock as evidence of earlier life on Mars, but this is controversial.

For the causes of the Cambrian Explosion , in 1997 he put forward the controversial thesis of an inertial exchange event (see also rare earth hypothesis ), according to which the main axes of inertia of the earth would have changed due to the continental drift and this would have changed the relative position of the earth's axis of rotation would have led to the earth's body with a rotation around the new axis, offset by around 90 degrees, with the greatest moment of inertia (they called the IITPW hypothesis for inertial interchange true polar wander ). At that time there was particularly rapid plate movement, the supercontinent Rodinia broke up and immediately afterwards the new supercontinent Gondwana formed. However, he also asserts less spectacular reasons. In some early bacterial species, such as Magnetospirillum magnetotacticum , magnetite played a role in the metabolism and, according to Kirschvink, living beings in the Cambrian succeeded in transferring the associated metabolic processes to other minerals such as calcite and thus forming shells and armor. In addition, sea transgressions during this period led to more sediment deposits and the migration of Laurentia and parts of Gondwana to equatorial latitudes led to more biodiversity due to the warmer climate. In the book with Peter Ward from 2015, they see the oxygen content of the atmosphere as an essential engine of evolution.

Kirschvink interprets small chains of magnetite crystals in living things as sensors for magnetic fields. He also found magnetite crystals in the human brain and is pursuing the possibility that humans, like some other animal species, also have a magnetic sense.

Honors

He won the Richard P. Feynman Prize for Teaching at Caltech and gave the 2001 Carl Sagan Memorial Lecture for the American Geophysical Union . He has been a member of the American Academy of Arts and Sciences since 2003 . In 2011 he received the William Gilbert Award from the American Geophysical Union.

The asteroid 27711 is named after him.

Fonts

  • with Peter Ward : A New History of Life: The Radical New Discoveries about the Origins and Evolution of Life on Earth. Bloomsbury Press, 2015.
    • German edition: A new history of life - How catastrophes have determined the course of evolution. Deutsche Verlags-Anstalt, 2016.
  • with Robert E. Kopp, Isaac A. Hilburn and Cody Z. Nash: The Paleoproterozoic snowball Earth: A climate disaster triggered by the evolution of oxygenic photosynthesis. In: Proc. Natl. Acad. Sci. USA Vol. 102, No. 32, 2005, pp. 11131-11136.
  • Late Proterozoic low-latitude glaciation: the snowball Earth. In: JW Schopf, C. Klein (Ed.): The Proterozoic Biosphere. Cambridge University Press, Cambridge 1992, pp. 51-52.
  • with Atsuko Kobayashi-Kirschvink and Barbara J. Woodford: Magnetite biomineralization in the human brain. In: Proc. Natl. Acad. Sci. UNITED STATES. Volume 89, 1992, pp. 7683-7687.
  • with Shih-Bin Robin Chang: Magnetofossils, the magnetization of sediments and the evolution of magnetite biomineralization. In: Ann. Rev. Earth Planet. Sci. Volume 17, 1989, pp. 169-195.
  • with Robert L. Ripperdan and David A. Evans: Evidence for a Large-Scale Reorganization of Early Cambrian Continental Masses by Inertial Interchange True Polar Wander. In: Science. Volume 277, No. 5325, 1997, pp. 541-545.
  • with LM Ward and WW Fischer: Timescales of Oxygenation Following the Evolution of Oxygenic Photosynthesis. In: Origins of Life and Evolution of Biospheres. Volume 46, March 2016, pp. 51-65.
  • with Ross N. Mitchell, Timothy D. Raub and Samuel C. Silva: Was the Cambrian explosion both an effect and an artifact of true polar wander? In: American J. Science. Volume 315, December 2015, pp. 945-995.
  • with Katie Thomas-Keptra ao: Elongated prismatic magnetite crystals in ALH84001 carbonate globules: Potential Martian magnetofossils. In: Geochimica et Cosmochimica Acta. Volume 64, 2000, pp. 4049-4081.

literature

  • Johann Grolle: Fertilization from space. In: Der Spiegel . No. 43, 2016, pp. 104-107.

Web links

Individual evidence

  1. ^ Joseph L. Kirschvink, Robert L. Ripperdan, and David A. Evans: Evidence for a Large-Scale Reorganization of Early Cambrian Continental Masses by Inertial Interchange True Polar Wander. In: Science. Volume 277, No. 5325, 1997, pp. 541-545.
  2. ↑ The possibility of such a great polar wandering has already been suggested by David Fisher: Some more remarks on polar wandering. In: J. Geophys. Research. Volume 79, 1974, p. 4041.
  3. ↑ Gilbert Award from AGU 2011 to Kirschvink
personal data
SURNAME Kirschvink, Joseph
ALTERNATIVE NAMES Kirschvink, Joe
BRIEF DESCRIPTION American geologist
DATE OF BIRTH 1953