Editing Mount Kilimanjaro (section)

=== Volcanology ===

The volcanic interior of Kilimanjaro is poorly known because there has not been any significant erosion to expose the [[igneous]] strata that comprise the volcano's structure.<ref name="Preliminary">{{cite journal |doi=10.1017/S0016756800066590 |bibcode=1956GeoM...93..218W |title=Preliminary Notes on the Geology of Kilimanjaro |journal=Geological Magazine |volume=93 |issue=3 |pages=218–228 |last1=Wilcockson |first1=W. H. |year=1956 |s2cid=128393681 }}</ref>

Eruptive activity at the Shira center commenced about 2.5 million years ago, with the last important phase occurring about 1.9 million years ago, just before the northern part of the edifice collapsed.<ref name="NonnottePhilippe"/> Shira is topped by a broad [[high plain]] at {{convert|3800|m|ft|abbr=on}}, which may be a filled [[caldera]]. The remnant caldera rim has been degraded deeply by erosion. Before the caldera formed and erosion began, Shira might have been between {{convert|4,900 and 5,200|m|abbr=on}} high. It is mostly composed of basaltic lavas, with some [[Pyroclastic rock|pyroclastics]]. The formation of the caldera was accompanied by lava emanating from [[Fracture (geology)|ring fractures]], but there was no large-scale [[Explosive eruption|explosive activity]]. Two cones formed subsequently, the [[phonolite|phonolitic]] one at the northwest end of the ridge and the [[diabase|doleritic]] Platzkegel in the caldera center.<ref name="NonnottePhilippe"/><ref name="Preliminary"/><ref>{{cite web |url=https://www.tranquilkilimanjaro.com/kilimanjaro-geology/ |website=Tranquil Kilimajaro |access-date=25 February 2024 |title=Kilimanjaro Geology |archive-date=25 June 2024 |archive-url=https://web.archive.org/web/20240625132954/https://www.tranquilkilimanjaro.com/kilimanjaro-geology/ |url-status=live }}</ref><ref name="JohnBarryDawson">{{cite book | author=John Barry Dawson | title=The Gregory Rift Valley and Neogene-recent Volcanoes of Northern Tanzania | url=https://books.google.com/books?id=Om2oMjXK3R4C&pg=PA56 | year=2008 | publisher=Geological Society of London | isbn=978-1-86239-267-0 | page=56 | access-date=2016-10-04 | archive-url=https://web.archive.org/web/20170223200626/https://books.google.com/books?id=Om2oMjXK3R4C&pg=PA56 | archive-date=2017-02-23 | url-status=live }}</ref>

Both Mawenzi and Kibo began erupting about 1 million years ago.<ref name="NonnottePhilippe"/> They are separated by the Saddle Plateau at {{convert|4400|m|ft|abbr=on}} elevation.<ref name="AnAscentOfKilimanjaro">{{cite journal |doi=10.2307/1780513 |jstor=1780513 |title=An Ascent of Kilimanjaro |journal=The Geographical Journal |volume=61 |issue=1 |pages=1–21 |last1=Gillman |first1=C. |year=1923 |bibcode=1923GeogJ..61....1G }}</ref>{{rp|3}}

The youngest dated rocks at Mawenzi are about 448,000 years old.<ref name="NonnottePhilippe"/> Mawenzi forms a horseshoe-shaped ridge with [[Rock pinnacle|pinnacles]] and ridges opening to the northeast, with a tower-like shape resulting from deep erosion and a [[mafic]] [[dike swarm]]. Several large [[cirque]]s cut into the ring and the largest of these sits on top of the Great Barranco gorge. Also notable are the East and West Barrancos on the northeastern side of the mountain. Most of the eastern side of the mountain has been removed by erosion. Mawenzi has a [[subsidiary peak]], Neumann Tower, {{convert|4425|m|ft|abbr=on}}.<ref name="NonnottePhilippe"/><ref name="Preliminary"/><ref name="JohnBarryDawson"/>

[[File:Kilimanjaro from Amboseli.jpg|thumb|left|Kilimanjaro in March 2012]]

Kibo is the largest cone on the mountain and is more than {{convert|24|km|mi|abbr=on}} wide at the Saddle Plateau altitude. The last activity here, dated to 150,000–200,000 years ago, created the current Kibo summit crater. Kibo still has gas-emitting [[fumarole]]s in its crater.<ref name="NonnottePhilippe"/><ref name="Preliminary"/><ref name="JohnBarryDawson"/> Kibo is capped by an almost symmetrical cone with [[escarpment]]s rising {{convert|180|to|200|m|abbr=on}} on the south side. These escarpments define a {{convert|2.5|km|mile|adj=mid|-wide|abbr=on}} caldera<ref name="Glaciers of Middle East"/> caused by the collapse of the summit.

Within this caldera is the Inner Cone and within the crater of the Inner Cone is the Reusch Crater, which the Tanganyika government in 1954 named after Gustav Otto Richard Reusch, upon his climbing the mountain for the 25th time (out of 65 attempts during his lifetime).<ref>{{cite web | url=http://cvgs.cu-portland.edu/history/biographies/bio.cfm?id=529 | title=Gustav Otto Richard Reusch | publisher=The Center for Volga German Studies at Concordia University | work=Biographies | access-date=16 July 2015 | archive-url=https://web.archive.org/web/20151024111716/http://cvgs.cu-portland.edu/history/biographies/bio.cfm?id=529 | archive-date=24 October 2015  }}</ref><ref>{{cite book | author=Richard Leider | title=The Power of Purpose: Find Meaning, Live Longer, Better | url=https://archive.org/details/The_Power_of_Purpose_2nd_9781605095271 | url-access=registration | date=10 May 2010 | publisher=Berrett-Koehler Publishers | isbn=978-1-60509-527-1 | page=[https://archive.org/details/The_Power_of_Purpose_2nd_9781605095271/page/n26 12] | access-date=4 October 2016 }}</ref> The Ash Pit, {{convert|350|m|ft|abbr=on}} deep, lies within the Reusch Crater.<ref>{{cite web | url=http://volcano.oregonstate.edu/kilimanjaro | title=Kilimanjaro | publisher=Oregon State University | work=Volcano World | date=25 April 2011 | access-date=16 July 2015 | archive-url=https://web.archive.org/web/20150718113556/http://volcano.oregonstate.edu/kilimanjaro | archive-date=18 July 2015 | url-status=live }}</ref> About 100,000 years ago, part of Kibo's crater rim collapsed, creating the area known as the [[Western Breach]] and the Great Barranco.<ref>{{cite book | author=Alex Stewart | title=Kilimanjaro: A Complete Trekker's Guide: Preparations, practicalities and trekking routes to the 'Roof of Africa' | url=https://books.google.com/books?id=28N6F2wBSM8C&pg=PA97 | date=23 April 2012 | publisher=Cicerone Press Limited | isbn=978-1-84965-622-1 | page=100 | access-date=4 October 2016 | archive-url=https://web.archive.org/web/20170223175534/https://books.google.com/books?id=28N6F2wBSM8C&pg=PA97 | archive-date=23 February 2017 | url-status=live }}</ref>

An almost continuous layer of lava buries most older geological features, except exposed [[Stratum|strata]] within the Great West Notch and the Kibo Barranco. The former exposes intrusions of [[syenite]].<ref name="Preliminary"/> Kibo has five main lava formations:<ref name="NonnottePhilippe"/>

* [[Phonotephrite]]s and [[tephriphonolite]]s of the Lava Tower group, on a [[Dike (geology)|dyke]] cropping out at {{convert|4600|m|ft|abbr=on}}, dated to 482,000 years ago.
* Tephriphonolite to phonolite lavas "characterized by rhomb mega-phenocrysts of sodic feldspars" of the Rhomb Porphyry group, dated to 460,000–360,000 years ago.
* [[Phenocryst|Aphyric]] phonolite lavas, "commonly underlain by basal obsidian horizons", of the Lent group, dated to 359,000–337,000 years ago
* [[Porphyry (geology)|Porphyritic]] tephriphonolite to phonolite lavas of the Caldera Rim group, dated to 274,000–170,000 years ago
* Phonolite lava flows with [[aegirine]] [[phenocryst]]s, of the Inner Crater group, which represents the last volcanic activity on Kibo

Kibo has more than 250 [[parasitic cone]]s on its northwest and southeast flanks that were formed between 150,000 and 200,000 years ago<ref name="NonnottePhilippe"/> and erupted [[picrobasalt]]s, [[trachybasalt]]s, [[ankaramite]]s, and [[basanite]]s.<ref name="NonnottePhilippe"/><ref name="Preliminary"/><ref name="JohnBarryDawson"/> They reach as far as [[Lake Chala]] and [[Taita-Taveta County|Taveta]] in the southeast and the Lengurumani Plain in the northwest. Most of these cones are well preserved, except the Saddle Plateau cones which were heavily affected by glacial action. Despite their mostly small size, lava from the cones has obscured large portions of the mountain. The Saddle Plateau cones are mostly cinder cones with terminal effusion of lava, while the Upper Rombo Zone cones mostly generated lava flows. All Saddle Plateau cones predate the last glaciation.<ref name="Preliminary"/>

According to reports gathered in the 19th century from the [[Maasai people|Maasai]], Lake Chala on Kibo's eastern flank was the site of a village that was destroyed by an eruption.<ref name="ShearsonHyland"/>