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<p><b>New page</b></p><div>{{Short description|Landform in Thunder Bay district, Ontario}}<br />
The '''Coldwell Complex''' is a large circular [[gabbro]] and [[syenite]] [[intrusion]] within the Earth's [[crust (geology)|crust]]. Located on the [[North Shore (Lake Superior)|North Shore]] of [[Lake Superior]] in [[Ontario]], [[Canada]], it is the largest [[alkaline]] [[intrusion]] in [[North America]] with a diameter of {{convert|25|km|mi|0|abbr=on}}.<ref>[http://mgmudrey.brinkster.net/Compressed/ILSG%2023rd%20Meeting%20Coldwell%20OCR.CV.pdf Twenty Third Annual Meeting Thunder Bay Ontario: Institute on Lake Superior Geology] {{webarchive|url=https://web.archive.org/web/20110515163858/http://mgmudrey.brinkster.net/Compressed/ILSG%2023rd%20Meeting%20Coldwell%20OCR.cv.pdf |date=2011-05-15 }}</ref><br />
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==Formation==<br />
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The Coldwell Complex has its origins in the [[Midcontinent Rift System]] about 1,100 million years ago. It is an exposed [[magma chamber]] that formed beneath the surface causing surface swelling to occur. This swelling turned into an active volcano, erupting [[basalt]]ic [[magma]]. 600 million years ago, the volcano walls became so large and heavy, they caved in on the volcano, acting as a cap. The magma then became trapped in the magma chamber where it settled and cooled with other minerals causing the initial phases of the complex. Glacial erosion stripped away the top layers of the volcano. Today, the once-hot magma chamber is exposed to surface rock on the northern shore of [[Lake Superior]].<br />
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==See also==<br />
*[[Volcanism of Canada]]<br />
*[[Volcanism of Eastern Canada]]<br />
*[[Midcontinent Rift System]]<br />
*[[Duluth Complex]]<br />
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==References==<br />
{{reflist}}<br />
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{{coord|48.748|N|86.435|W|display=title}}<br />
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[[Category:Volcanoes of Ontario]]<br />
[[Category:Proterozoic volcanism]]<br />
[[Category:Landforms of Thunder Bay District]]<br />
[[Category:Igneous intrusions]]<br />
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