Editing Richard Dixon Oldham

{{Short description|British geologist}}
{{Use dmy dates|date=August 2015}}
{{Use British English|date=August 2015}}
{{Infobox scientist
|name              = Richard Dixon Oldham
|image             = RD Oldham.gif
|image_size        = 150px
|caption           = Richard Dixon Oldham
|birth_date        = {{Birth date text|31 July 1858|31 July 1858}} 
|birth_place       = [[Dublin]]
|death_date        = {{death date text|15 July 1936|15 July 1936}} (age 77) 
|death_place       = 
|residence         = 
|citizenship       = 
|nationality       = British
|ethnicity         = 
|field             = [[Geology]]
|work_institutions = 
|alma_mater        = 
|doctoral_advisor  = 
|doctoral_students = 
|known_for         = measuring Earth's core; separate arrival of seismic phases
|author_abbrev_bot = 
|author_abbrev_zoo = 
|influences        = 
|influenced        = 
|prizes            = 
|religion          = 
|footnotes         = 
|signature         =
}}

'''Richard Dixon Oldham''' [[Fellow of the Royal Society|FRS]] ({{IPAc-en|ˈ|oʊ|l|d|ə|m}}; 31 July 1858 &ndash; 15 July 1936) was a British geologist who made the first clear identification of the separate arrivals of [[P-wave]]s, [[S-wave]]s and [[Seismic wave#Surface waves|surface waves]] on [[seismogram]]s and the first clear evidence that the Earth has a central core.

==Life==

Born on 31 July 1858 to [[Thomas Oldham]], a [[Fellow of the Royal Society]] and geologist, Oldham was educated at [[Rugby School]] and the [[Royal School of Mines]].
<ref name=Bragg>{{cite journal|last=Bragg|first=W.|title=Tribute to deceased fellows of the Royal Society|journal=Science|year=1936|volume=84|issue=2190|pages=539&ndash;546|doi=10.1126/science.84.2190.539 |pmid=17834950|bibcode = 1936Sci....84..539B }}</ref>

In 1879 Oldham became an assistant-superintendent with the [[Geological Survey of India]], working in the [[Himalayas]]. He wrote about 40 publications for the Survey on geological subjects including hot springs, the geology of the Son Valley and the structure of the Himalayas and the [[Indo-Gangetic Plain|Ganges plain]].<ref name=Biography2008>{{cite encyclopedia |title=Oldham, Richard Dixon |encyclopedia=Complete Dictionary of Scientific Biography |volume=10 |publisher=[[Charles Scribner's Sons]] |year=2008 |page=203}}</ref> His most famous work was in seismology. His report on the [[1897 Assam earthquake]] went far beyond reports of previous earthquakes. It included a description of the Chedrang fault, with uplift up to 35 feet and reported accelerations of the ground that had exceeded the [[Gravity of Earth|Earth's gravitational acceleration]]. He also included accounts of earth-waves that could be seen travelling across the plain, and of waterspouts.{{sfn|Oldham|1899}}<ref name=Biography2008/> During the cold season following the earthquake, the Survey carried out a re-triangulation of part of the area that had been initially surveyed in 1860. They found displacements of up to 12 feet both in distances and heights, substantially larger than could be due to errors. This was one of the earliest reports of such a re-survey.{{r|Biography2008|pages=361-371}}
{{Gallery| width=275 |height=275
 |Oldham_1899_Plate_42_memoirsofgeologi29geol_0541.jpg |Sketch map of the Samin and Chedrang faults, showing the uplift in feet.
 |Oldham 1899 Plate 15 memoirsofgeologi29geol 0477.jpg|The Chedrang fault cutting the bed of the Chedrang River. The fault face forms the right bank of the current watercourse, and part of the former bed of the river can be seen above the fault face.
 |Oldham 1899 Frontispiece memoirsofgeologi29geol 0008.jpg|Monument to George Inglis, Chatak, showing the upper part twisted with respect to the base.
}}

Oldham's most important contribution to seismology was the first clear identification of the separate arrivals of different groups of waves, as detected by [[seismogram]]s at distant locations. In the report of the 1897 earthquake he presented data, mainly from stations in Italy, that showed three phases. The first to arrive, the [[P-wave|P or Primary waves]], were compression waves, which he referred to as condensational.  Next came the [[S-wave|S or Secondary waves]], with lateral movement, which he referred to as distortional. The third phase was of large undulations. The times of arrival of these phases indicated that the first two had travelled through the body of the  earth, while the third were [[Seismic wave#Surface waves|surface waves]].{{sfn|Oldham|1899}} Since these observations agreed with theory for [[Linear elasticity#Elastodynamics in terms of displacements|elastic waves]], they showed that the Earth could be treated as elastic in studies of seismic waves.<ref name=Biography2008/>

[[File:Transmission of Eathquake Waves Oldham 1906 Figure 3 14.png|thumb|left|Transmission of earthquake waves, as affected by the presence of a core of 0.4 of the earth's diameter. From Oldham (1906)]]
[[File:San Andreas Fault Oldham 1909 2.png|thumb|Map of the San Andreas Fault, California, showing displacements due to the [[1906 San Francisco earthquake|1906 Earthquake]]. From Oldham (1909)]]
In subsequent papers, Oldham compared data from numerous earthquakes, with seismic observations at different distances from the epicentre. He found a discontinuity in the travel times for the S-waves at about 120° angular distance from the earthquake, suggesting refraction by a dense core with a diameter of about 0.4 that of the earth.{{sfn|Oldham|1900}}{{sfn|Oldham|1906}}<ref name=Bragg/><ref>{{cite book |last1=Oldroyd |first1=David |title=Thinking about the Earth: A History of Ideas in Geology |date=1996 |publisher=Harvard University Press |isbn=9780674883826 |pages=234–236}}</ref> Oldham was not the first to suggest that the earth had a dense core, but he provided the first direct evidence of its existence and size.<ref>{{cite journal |last1=Brush |first1=Stephen G. |title=Discovery of the Earth's core |journal=American Journal of Physics |date=1980 |volume=48 |issue=9 |pages=705–724 |doi=10.1119/1.12026|bibcode=1980AmJPh..48..705B }}</ref>

In 1903, Oldham resigned from the GSI due to ill-health and returned to the United Kingdom, living in [[Kew]] and various parts of [[Wales]].<ref name="frs"/>{{rp|110}} He continued to be active in the field, publishing papers on earthquakes in Guatemala and California.

In 1908 Oldham was awarded the [[Lyell Medal]], in 1911 made a [[Fellow of the Royal Society]],<ref name="frs">{{cite journal|last=Davison|first=C.|title=Richard Dixon Oldham. 1858-1936|journal=Obituary Notices of Fellows of the Royal Society|year=1936|volume=2|issue=5|pages=111&ndash;113|doi=10.1098/rsbm.1936.0008 }}</ref> and from 1920 to 1922 served as the [[President of the Geological Society of London]]. Later in his life he became interested in the geography and history of the [[Rhône]] delta. He died on 15 July 1936.<ref name="frs"/>{{rp|113}}

== See also ==
* [[Harold Jeffreys]] &ndash; showed that [[Earth's outer core]] is liquid
* [[Inge Lehmann]] &ndash; showed that [[Earth's inner core]] is solid
* [[List of geophysicists]]

==References==
{{Reflist}}

==Publications==
{{Wikisource author}}
*{{cite journal |last1=Oldham |first1=R.D. |title=Report on the geology of parts of Manipur and the Naga Hills |journal=Memoirs of the Geological Survey of India |date=1883 |volume=19 |issue=4 |url=https://archive.org/details/oldham-1883-xix-pt-4-memoirsofgeolog-191883geol}}
*{{cite journal |last1=Oldham |first1=R.D. |author-mask=2 |title=Essays on Speculative Geology. 1. - On Homotaxis and Contemporaneity |journal=Geological Magazine |date=1886 |volume=3 |issue=7 |pages=293–300 |doi=10.1017/S0016756800145121 |bibcode=1886GeoM....3..293O |s2cid=129631499 |url=https://archive.org/details/oldham-1886a-geologicalmagazi-3318wood}}
*{{cite journal |last1=Oldham |first1=R.D. |author-mask=2 |title=Essays on Speculative Geology. 2 - Probable Changes of Latitude |journal=Geological Magazine |date=1886 |volume=3 |issue=7 |pages=300–308 |doi=10.1017/S0016756800145133 |bibcode=1886GeoM....3..300O |s2cid=128492838 |url=https://archive.org/details/oldham-1886-geologicalmagazi-3318wood}}
*{{cite book |last1=Oldham |first1=Richard Dixon |author-mask=2 |title=A Bibliography of Indian Geology: Being a List of Books and Papers, Relating to the Geology of British India and Adjoining Countries, Published Previous to the End of AD 1887 |date=1888 |publisher=Superintendent, Government Printing, India |location=Calcutta |url=https://archive.org/details/bibliographyofin00oldhrich}}
*{{cite journal |last1=Oldham |first1=R.D. |author-mask=2 |title=The Evolution of Indian Geography |journal=The Geographical Journal |date=1894 |volume=3 |issue=3 |pages=169–192 |doi=10.2307/1773463 |jstor=1773463 |url=https://archive.org/details/dli.pahar.1320}}
*{{cite journal|last=Oldham|first=R. D. |author-mask=2 |title=Report of the great earthquake of 12th June, 1897 |journal=Memoirs of the Geological Society of India |volume=29 |publisher=K. Paul, Trench, Trübner & co. |year=1899 |url=https://archive.org/details/memoirsofgeologi29geol }}
*{{cite journal |title=On the Propagation of Earthquake Motion to Great Distances |first=R. D. |last=Oldham |author-mask=2 |journal=[[Philosophical Transactions of the Royal Society A]] |volume=194 |year=1900 |issue=252–261 |pages=135&ndash;174 |url=https://archive.org/details/philtrans09521374 |bibcode = 1900RSPTA.194..135O |jstor=90755 |doi = 10.1098/rsta.1900.0015 |doi-access= }}
*{{cite journal |last1=Oldham |first1=Richard Dixon |author-mask=2 |title=On the Origin of the Dunmail Raise (Lake District) |journal=Quarterly Journal of the Geological Society |date=1901 |volume=57 |issue=1–4 |pages=189–197 |doi=10.1144/GSL.JGS.1901.057.01-04.14 |s2cid=128700544 |url=https://archive.org/details/oldham-1901-quarterlyjourn-571901geol}}
*{{cite journal |last1=Oldham |first1=Richard Dixon |author-mask=2 |title=On Tidal Periodicity in the Earthquakes of Assam |journal=Journal of the Asiatic Society of Bengal |date=1902 |volume=71 |pages=139–153 |url=https://archive.org/details/ontidalperiodic00oldhgoog}}
*{{cite journal |last1=Oldham |first1=R.D. |author-mask=2 |title=The Rate of Transmission of the Guatemala Earthquake, April 19, 1902 |journal=Proceedings of the Royal Society of London. Series A |date=1905 |volume=76 |issue=508 |pages=102–111 |doi=10.1098/rspa.1905.0007 |bibcode=1905RSPSA..76..102O |url=https://archive.org/details/philtrans05279386|doi-access=free }}
*{{cite journal|last=Oldham|first=R. D. |author-mask=2 |title=The Constitution of the Interior of the Earth, as Revealed by Earthquakes|journal=Quarterly Journal of the Geological Society|year=1906|volume=62|issue=1–4|pages=456–475|doi=10.1144/GSL.JGS.1906.062.01-04.21 |s2cid=129025380|url=https://archive.org/details/oldham-1906-quarterlyjournal-62190geol}}
*{{cite journal |last1=Oldham |first1=Richard Dixon |author-mask=2 |title=The Constitution of the Interior of the Earth, as revealed by Earthquakes:(Second Communication). Some New Light on the Origin of the Oceans |journal=Quarterly Journal of the Geological Society |date=1907 |volume=63 |issue=1–4 |pages=344–350 |doi=10.1144/GSL.JGS.1907.063.01-04.24 |s2cid=140737052 |url=https://archive.org/details/oldham-1907-quarterlyjournal-63190geol}}
*{{cite journal |last1=Oldham |first1=Richard Dixon |author-mask=2 |title=The Geological Interpretation of the Earth - Movements associated with the Californian Earthquake of April 18th, 1906 |journal=Quarterly Journal of the Geological Society |date=1909 |volume=65 |issue=1–4 |pages=1–20 |doi=10.1144/GSL.JGS.1909.065.01-04.03 |s2cid=129314512 |url=https://archive.org/details/oldham-1909-quarterlyjourna-651909geol}}
*{{cite journal |last1=Oldham |first1=R.D. |author-mask=2 |title=On the Effect of the Gangetic Alluvium on the Plumb-Line in Northern India |journal=Proceedings of the Royal Society of London. Series A |date=1914 |volume=90 |issue=615 |pages=32–41 |doi=10.1098/rspa.1914.0032 |url=https://archive.org/details/philtrans00601539 |jstor=93566|bibcode=1914RSPSA..90...32O |doi-access=free }}
*{{cite journal |last1=Oldham |first1=R.D. |author-mask=2 |title=The constitution of the interior of the Earth as revealed by earthquakes |journal=Nature |date=1914 |volume=92 |issue=2312 |pages=684–685 |doi=10.1038/092684c0 |bibcode=1914Natur..92..684O |s2cid=28807716 |url=https://archive.org/details/paper-doi-10_1038_092684c0}}
*{{cite journal |last1=Oldham |first1=Richard Dixon |author-mask=2 |title=The structure of the Himalayas and of the Gangetic plain: as elucidated by geodetic observations in India |journal=Memoirs of the Geological Survey of India |date=1917 |volume=42 |issue=2 |url=https://archive.org/details/oldham-1917-geological-surve-xliin}}
*{{cite journal |last1=Oldham |first1=R.D. |author-mask=2 |title=The Portolan Maps of the Rhône Delta: A Contribution to the History of the Sea Charts of the Middle Ages |journal=The Geographical Journal |date=1925 |volume=65 |issue=5 |pages=403–425 |doi=10.2307/1782548 |jstor=1782548 |url=https://archive.org/details/oldham-1925-sim-geographical-journal-1925-05-65-5}}
*{{cite journal |last1=Oldham |first1=R.D. |author-mask=2 |title=The Post-Roman History of the Rhone Delta |journal=Science Progress in the Twentieth Century (1919-1933) |date=1926 |volume=20 |issue=79 |pages=487–496 |jstor=43428312 }}
*{{cite journal |last1=Oldham |first1=R.D. |author-mask=2 |title=The depth and twofold character of earthquake origins |journal=The Journal of Geology |date=1926 |volume=34 |issue=5 |pages=385–398 |doi=10.1086/623325|bibcode=1926JG.....34..385O |s2cid=129529277 }}
*{{cite book|last1=Oldham |first1=Thomas |editor-last1=Oldham |editor-first1=R.D.|title=Geological Glossary: For the Use of Students|url=https://archive.org/details/geologicalgloss01oldhgoog|year=1879|publisher=E. Stanford}}
*{{cite journal |last1=Oldham |first1=Thomas |editor-last1=Oldham |editor-first1=R.D.|title=The Cachar earthquake of 10th January 1869 |journal=Memoirs of the Geological Survey of India |date=1882 |volume=19 |issue=1 |url=https://archive.org/details/oldham-1882-xix-pt-1-memoirsofgeolog-191883geol}}
*{{cite journal |last1=Oldham |first1=Thomas |editor-last1=Oldham |editor-first1=R.D.|title=The Thermal Springs of India |journal=Memoirs of the Geological Survey of India |date=1882 |volume=19 |issue=2 |url=https://archive.org/details/oldham-1882-xix-pt-2-memoirsofgeolog-191883geol}}
*{{cite book |last1=Medlicott |first1=Henry Benedict |last2=Blanford |first2=William Thomas |last3=Oldham |first3=Richard Dixon |title=A Manual of the Geology of India: Chiefly Compiled from the Observations of the Geological Survey: Stratigraphical and Structural Geology |date=1893 |publisher=Office of the Superintendent of Government Printing |location=Calcutta |url=https://archive.org/details/cu31924003933409}}

==External links==
{{commons category|Richard Dixon Oldham}}
*[http://cires.colorado.edu/~bilham/Oldham.htm Oldham]

{{GLS Presidents}}

{{Authority control}}

{{DEFAULTSORT:Oldham}}
[[Category:1858 births]]
[[Category:1936 deaths]]
[[Category:British geologists]]
[[Category:British seismologists]]
[[Category:Fellows of the Royal Society]]
[[Category:Lyell Medal winners]]
[[Category:Presidents of the Geological Society of London]]