'''Thordarhyrna''' (also known as Þórdarhyrna) is one of seven <ref>[http://deposit.ddb.de/cgi-bin/dokserv?idn=991146220&dok_var=d1&dok_ext=pdf&filename=991146220.pdf]Figure 2.8 shows 7 volcanoes beneath the glacier</ref> subglacial volcanos in the western part of [[Vatnajokull]] glacier Iceland.

It last erupted in 1910 and prior to that in 1903<ref>[http://www.extremeiceland.is/en/eruptions-in-iceland-since-1900] Eruptions in Iceland since 1900 </ref>

There is a mechanical interaction between Thordarhyrna and [[Grimsvötn]], despite these volcanoes being comparatively far apart <ref>[http://www.google.co.uk/url?sa=t&source=web&cd=1&sqi=2&ved=0CBgQFjAA&url=http%3A%2F%2Flinkinghub.elsevier.com%2Fretrieve%2Fpii%2FS0377027308004393&rct=j&q=thordarhyrna&ei=FSfbTYD4F9C4hAeFgpmnDw&usg=AFQjCNFMLr2U8cOq6N3sHedSqSpmSPqG5w&cad=rja]</ref> so the eruption from 1902 - 1904 was combined with an eruption from Grimsvötn and had a [[Volcanic Explosivity Index]] (VEI): 4 <ref>[http://www.volcano.si.edu/world/volcano.cfm?vnum=1703-01=&volpage=erupt</ref>

While an eruption 1887 to 1889 eruption had a (VEI): 2 <ref>[http://www.volcano.si.edu/world/volcano.cfm?vnum=1703-01=&volpage=erupt</ref>

An eruption in 3550 BC +/- 500 years poured out 1,500,000,000 cubic meters of lava <ref>[http://www.volcano.si.edu/world/volcano.cfm?vnum=1703-01=&volpage=erupt</ref> in the area south of Thordarhyrna ([[Bergvatnsarhraun]])

A fault runs (N.35°W) from Thordarhyrna towards [[Hamarinn]], and separates two, markedly-different, tectonic regimes. <ref>[http://www.igsoc.org/login/?returnto=/annals/8/igs_annals_vol08_year1985_pg11-18.pdf] Surface and bedrock topography mapped by radio echo sounding</ref>

===See also===
[[List of volcanoes in Iceland]]

===References===
{{Reflist}}

[[Category:Geology stubs]]