Mount Morning

Mount Morning is a shield volcano at the foot of the Transantarctic Mountains in Victoria Land, Antarctica. It lies Template:Convert from Ross Island. Mount Morning rises to an elevation of Template:Convert and is almost entirely mantled with snow and ice. A Template:Convert wide summit caldera lies at the top of the volcano and several ice-free ridges such as Hurricane Ridge and Riviera Ridge emanate from the summit. A number of parasitic vents mainly in the form of cinder cones dot the mountain.

The volcano was initially active during the Miocene and erupted in two separate stages with a hiatus in between. The older stage has a different chemical composition than the recent one and is heavily eroded by glaciers. The most recent parasitic vents were active about 20,000 years ago and the volcano could erupt again. Template:TOC limit

Geography and geomorphology

Mount Morning lies in Victoria Land,Template:Sfn about Template:Convert from Ross Island and at the foot of the Transantarctic Mountains.Template:Sfn The Koettlitz Glacier runs along the northwestern foot of Mount MorningTemplate:Sfn and separates it from the Royal Society RangeTemplate:Sfn Template:Convert away.Template:Sfn Mount Discovery lies next to Mount Morning and is separated from it by the Discovery Glacier.Template:Sfn The volcano was originally described in the early to middle 20th century, before more detailed analyses took place in the 1970s, 1980s and 2000s.Template:Sfn The climate in the area is polar,Template:Sfn although parts of the ice melt in the sunshine during summer.Template:Sfn

The volcano rises to Template:Convert above sea level and is capped by a Template:Convert wide calderaTemplate:Sfn that may be the source of a glacier at its northeastern end.Template:Sfn Mount Morning has been defined as a Template:Convert large shield volcanoTemplate:Sfn that consists of a central volcano overlying an older volcanic complex.Template:Sfn With a volume of Template:ConvertTemplate:Sfn it is one of the largest volcanoes in the region.Template:Sfn Fissure vents have producedTemplate:Sfn at least 185Template:Sfn parasitic vents on the slopes of Mount Morning.Template:Sfn They are cinder cones, fissure ridges, lava domes and volcanic necks,Template:Sfn and their diameters range from a few metres to a few hundred metres.Template:Sfn Many of the vents form alignments, some cone craters overlap or the vents themselves have linear shapes.Template:Sfn These linear patterns define northeast–southwest trends, with a minor northwest–southeast alignment.Template:Sfn Lava flows emanate from cones and make up the present-day surface of the volcano.Template:Sfn

Mount Morning is almost entirely covered with snow and iceTemplate:Sfn except where it is ablated by southerly winds.Template:Sfn Outcrops of volcanic rocks form the north-northeastern Riviera Ridge and northeastern Hurricane Ridge on the northern flank, Mason Spur on the southern flankTemplate:SfnTemplate:Sfn and on Helms Bluff on the eastern flank.Template:Sfn Gandalf Ridge is a promontoryTemplate:Sfn formed by northward-tilted debris and penetrated by Dikes.Template:Sfn It is located at the foot of Hurricane Ridge, and Pinnacle Valley is located on the Riviera Ridge.Template:Sfn Dikes, lava domes, lava flows and pyroclastic deposits are found in outcrops.Template:Sfn Mason Spur also contains breccias from pillow lavas, while Gandalf Ridge features a diamictiteTemplate:Sfn and a cross-cutting fault.Template:Sfn Mason Spur was considered by Martin et al. 2021 to be a separate volcano from Mount Morning.Template:Sfn

Owing to the lack of running water,Template:Sfn the main edifice (unlike Mason Spur,Template:Sfn where traces of marine and water erosion are presentTemplate:Sfn) is unerodedTemplate:Sfn and parasitic vents have a young appearance. Glacial erosion has eroded some parts of the volcano, leaving volcanic necks in Pinnacle Valley, has etched glacial striations into exposed volcanic rocksTemplate:Sfn and deposited glacial till.Template:Sfn The Vereyken Glacier descends the northeastern slopes of Mount Morning between Hurricane Ridge and Riviera Ridge. Moraines occur on these two ridgesTemplate:Sfn and moraines dating to the Wisconsin glaciation have been reported.Template:Sfn Glaciers descending from Mount Morning feed the Koettlitz Glacier.Template:Sfn Several lakes are found on the volcano and at its foot, including Lake Morning at the end of the Riviera RidgeTemplate:Sfn and Lake Discovery at the foot of the Hurricane and Gandalf ridges.Template:Sfn

File:MountDiscoveryMap.jpg

Topographic map of Mounts Morning and Discovery (1:250,000 scale) from USGS Mount Discovery

Geology

The West Antarctic Rift is a major geological feature in AntarcticaTemplate:Sfn and one of Earth's largest continental rifts.Template:Sfn It is a region of active crustal extension and spreading, which may be ongoing today. Volcanic activity occurs at the rift and includes the McMurdo Volcanic Group,Template:Sfn a Template:Convert long chain of volcanoes in Victoria Land. This volcanic group has erupted alkaline lavas during the course of the Cenozoic. It is subdivided into three provinces, the Hallett, the Melbourne and the Erebus province; Mount Morning is the southernmost volcano of the Erebus province.Template:Sfn

Mount Morning rises from a Paleozoic basement, the Koettlitz GroupTemplate:Sfn which crops out close to Gandalf RidgeTemplate:Sfn in the form of granite and metasedimentary rocks.Template:Sfn Based on rocks erupted by Mount Morning, the crust appears to be thin and has a calc-alkaline composition.Template:Sfn Tectonic sutures in this basement may have allowed magma to ascend to the surface in the Mount Morning region.Template:Sfn

Composition

Basanite is the dominant rock of outcrops,Template:Sfn with phonolite less common and picrobasalt and tephrite rare. Outcrops of older rocks include mugearite, rhyolite and trachyte.Template:Sfn Textures range from porphyritic to seriate. Various phenocrysts are found within the volcanic rocks, including aegirine, augite, clinopyroxene, alkali feldspar, kaersutite, nepheline, olivine, plagioclase, quartz and sanidine. Aegirine, aenigmatite, amphibole, augite, clinopyroxene, alkali feldspar, glass, iron oxide-titanium oxide, nepheline, plagioclase and quartz make up the groundmass.Template:Sfn The volcanic rocks contain xenoliths consisting of syeniteTemplate:Sfn and of rocks from older stages of Mount Morning activity.Template:Sfn Spinel peridotite and less commonly clinopyroxenite, dunite, harzburgite, lherzolite, norite, pyroxenite and websterite have been reported as xenoliths.Template:Sfn

The early volcanic rocks of Mount Morning are comparable to mildly alkaline rocks from Mount Melbourne, while the more alkaline late volcanic rocks resemble these from Mount Erebus.Template:Sfn The older rocks define the "Mason Spurr lineage" while the younger ones are referred to as the "Riviera Ridge lineage".Template:Sfn Basaltic rocks are concentrated on the lower slopes, while phonolite is mainly found in the upper sector of Mount Morning.Template:Sfn The composition changes between the early and late volcanic activity of Mount Morning may be due to alteration in crustal magma processes.Template:Sfn

Eruption history

Mount Morning has been active during the Miocene,Template:Sfn Pliocene and Pleistocene.Template:Sfn Argon-argon dating and potassium-argon dating have been used to infer the duration of volcanic activity at Mount Morning. Gandalf Ridge has yielded ages of 18.7±0.3-15.5±0.5 million years, Pinnacle Valley 15.2±0.2-13.0±0.3 million years, Mason Spur 12.8±0.4-11.4±0.2 million years, rocks below the summit of 6.13±0.20-~1.00 million yearsTemplate:Sfn and 4.51±0.31-0.02 million years on other formations.Template:Sfn Some of these eruptions may have deposited volcanic ash over the McMurdo Sound areaTemplate:Sfn and in the Transantarctic Mountains.Template:Sfn Even older activity at Mount Morning may be recorded in volcanic deposits from Cape RobertsTemplate:Sfn which go back to 24.1 million years ago. This is a long lifespan for a volcano by Antarctic standards, and may be due to tectonic factors that kept magma generation focused on Mount Morning for a long time.Template:Sfn Loading by glaciers may have influenced volcanic activity at Mount Morning,Template:Sfn and conversely, the growth of Mount Morning and Discovery may have formed substrates for the formation of new glaciers - initially the mountains may not have had much glaciation.Template:Sfn

Volcanic activity has been subdivided into two phases separated by a hiatus, an early phase lasting between 11.4±0.2-18.7±0.3 million years ago and a late phase from 6.13±0.02 million years ago to almost present-day.Template:Sfn These phases are also known as the phase I or the Mason Spur Lineage, and as the phase II or the Riviera Ridge Lineage.Template:Sfn The early phase produced mildly alkaline volcanic rocks, the late phase which makes up most of the outcrops strongly alkaline rocks.Template:Sfn The early phase has produced ignimbrites from a caldera at Mason Spur, an otherwise rare type of volcanoes in Antarctica.Template:Sfn The older rocks have undergone significant glaciation, while the younger ones are largely unerodedTemplate:Sfn and make up the present-day edifice.Template:Sfn Volcanic activity mostly occurred under the atmosphere, with the exception of some lavas that may have been erupted in a subaqueous environmentTemplate:Sfn and hyaloclastites which have been used to infer that glaciers existed there 15.4 million years ago.Template:Sfn Volcanic activity was focused along geologic lineaments on Mount Morning, which were reused during more recent eruptions.Template:Sfn

Eruptions took place at Mount Morning about 20,000 years ago, forming well-preserved cinder cones. In the 1960s thermal anomalies were observed at Gandalf Ridge, implying that the volcano may still be active,Template:Sfn although ground surveys did not detect fumarolic activity.Template:Sfn Thus, Mount Morning was considered dormant by Martin, Cooper and Dunlap 2010Template:Sfn and might be the source of tephra layers found in the area.Template:Sfn

History and name

The volcano was discovered by the Discovery Expedition in 1901-1904 and named after a relief ship that took part in the expedition.Template:Sfn

Features

Template:GeoGroup Features, from north to south, include:

Gandalf Ridge

Template:Coord A volcanic ridge at the northwest end of Hurricane Ridge, to the north of Mount Morning on Scott Coast. Gandalf is a whimsical name put forward by geologist Philip R. Kyle, Institute of Polar Studies, The Ohio State University, who examined the ridge in December 1977. The discovery of very hard volcanic rock at this ridge led to the naming: Gandalf, after a crusty character (a wizard) in J.R.R. Tolkien's Lord of the Rings.Template:Sfn

Hurricane Ridge

Template:Coord. The eastern of two broad, mainly ice-free ridges that descend north from Mount Morning. Riviera Ridge is the other, to the west, and Gandalf Ridge and Lake Discovery are located at the north end of this ridge. The name was suggested by geologist Anne C. Wright, Department of Geoscience, New Mexico Institute of Mining and Technology, a member of the NMUMT field party that camped on the ridge in the 1985–86 season. The party's tent was blown to shreds by 100-knot winds, requiring evacuation of the party by helicopter. This ridge is renowned for consistently strong winds. Juxtaposed with Riviera Ridge, which is similar in appearance to this ridge to the west.Template:Sfn

Vereyken Glacier

Template:Coord A glacier which, together with Morning Glacier, drains the northeast slopes of Mount Morning. Vereyken Glacier flows north between Riviera Ridge and Hurricane Ridge into Koettlitz Glacier. Named by US-ACAN (1994) after Jill Vereyken, ASA manager of Field Support Services, McMurdo Station, who was active in coordination and planning of science support in Antarctica from 1984.Template:Sfn

Riviera Ridge

Template:Coord. This name has been included as a US-ACAN proposal even though it was apparently applied in about 1977 by Anne Wright (now Grassham) who worked on the ridge with P.M. Kyle. The name alludes to the warm sunny conditions experienced on the ridge in contrast to the storm conditions previously experienced on nearby "Hurricane Ridge".Template:Sfn

Testa Ridge

Template:Coord A volcanic ridge, Template:Convert, extending north–south between Weidner Ridge and Riviera Ridge on the north slope of Mount Morning. Named by Advisory Committee on Antarctic Names (US-ACAN) (1994) after J. Ward Testa, biologist, University of Minnesota (later of University of Alaska); conducted seal studies during ten field seasons in McMurdo Sound and other coastal regions, 1980–94.Template:Sfn

Campbell Crag

Template:Coord A rock peak rising to Template:Convert high at the south end of Testa Ridge on the north slope of Mount Morning. Named by US-ACAN (1994) after Richard J. (Rick) Campbell, ASA, fixed-wing Flight Operations Coordinator at McMurdo Station, active in science support in Antarctica from 1981.Template:Sfn

Weidner Ridge

Template:Coord. A linear volcanic outcrop, approximately Template:Convert long, between and parallel to Savage Ridge and Testa Ridge on the north slope of Mount Morning. Named by US-ACAN after George A. Weidner, Department of Meteorology (later Space Science and Engineering Center), University of Wisconsin. Along with Charles Stearns he developed the use of automatic weather stations in Antarctica in the period 1982–2005.Template:Sfn

Savage Ridge

Template:Coord. A linear volcanic outcrop approximately Template:Convert long descending from the northwest slope of Mount Morning. Parallel to and about Template:Convert from Weidner Ridge. Named by US-ACAN (1994) after Michael L. Savage, Department of Meteorology, University of Wisconsin. Along with Charles Stearns, he developed the use of automatic weather stations in Antarctica during four field seasons, 1980–86.Template:Sfn

Morning Glacier

Template:Coord. A glacier on the northeast slope of Mount Morning. The glacier flows from the peak for about Template:Convert, terminating partway down the mountain, approximately Template:Convert south of Lake Morning, and west of the upper Vereyken Glacier. Named by US-ACAN (1994) in association with Mount Morning.Template:Sfn

Mason Spur

Template:Coord. An elevated spur, partially ice-covered and over Template:Convert high, which projects eastward from Mount Morning. Named by US-ACAN in 1963 for Robert Mason, USARP Representative at McMurdo Station, 1962–63.Template:Sfn

References

Sources

• Template:Include-USGov
• Template:Cite gnis2
• Template:Cite gnis2
• Template:Cite gnis2
• Template:Cite gnis2

External links

• Template:Cite thesis
• Template:Cite thesis
• Template:Cite thesis
• Template:Cite thesis
• Template:Cite thesis
• Template:Cite thesis
• Polar Discovery: Mount Morning Lava Flows