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"Geology." National Parks Service. U.S. Department of the Interior, 01 Aug. 2015. Web.
"Glacier National Park." NPS: Nature & Science. N.p., n.d. Web.
Ringing Rocks." Bureau of Land Management. N.p., 28 June 2012. Web.
"Ringing Rocks Pluton, Jefferson County, Montana." Wikipedia. Wikimedia Foundation, n.d. Web.
"Rock Music in the Boulder Batholith." Montana Earth Science. N.p., n.d. Web.
Ringing Rocks photo and video credit go to me (Karisha Omkar).
Information credit also goes to the Boulder Batholith and Ringing Rocks primer and The Belt Supergroup in Glacier National Park primer (put together by Zack Sauter).
Approximately 150 million years ago, the crustal plates collided and resulted in the beginning of mountain building processes inland that would continue up until 60 million years ago. In the area that would eventually become Glacier National Park, massive forces uplifted a slab of rock several miles thick, which slid about 50 miles east over much younger rock which would come to be known as the Lewis Overthrust Fault.
The overlying Precambrian (Proterozoic) rocks are over 1,400 million years older than the underlying Cretaceous age rocks upon which they were uplifted onto. It has also functioned to expose ancient sediments with an unparalleled degree of preservation.
At the same time the uplift was occurring, many other events were happening at the same time, such as synclinal folding and other types of faulting, which is evident in the park.
As a result of the uplift, erosive forces accelerated and over several million years removed the upper layers of material, leaving behind the rock formations found today, such as Chief Mountain. Chief Mountain is an isolated remnant of the eastern edge of the upper plate of the Lewis Overthrust, a feature known as a klippa.
However, many of the Proterozoic age rocks of Glacier are unique, as they are virtually unaltered, having preserved the subtle features of sedimentation, such as mud cracks, raindrop impressions, fossil algae, and ripple marks.
Most of the rocks exposed in Glacier are sedimentary rocks of the Belt Series. They are Mesoproterozoic in age and were deposited from around 1,600 to 800 million years ago.
These same belt rocks make up the Lewis Thrust. From the Altyn formation, it gets lighter colors of limestone, dolomite, quartz, and some feldspar. The Prichard formation gives it dark grey to black siltite and argillite. Greenish grey siltite and agrillite, along with thick beds of quartzite comes from the Appekuny Formation. The Grinnell and Empire both add some more siltite and agrillite, though the Grinnell adds a bit of quartzite too. The Helena adds more limestone and dolomite and an intrusion of igneous sill, diorite.
Chief Mountain
The Ringing Rocks make strange ringing noises when struck. The reason why is unknown, but if any are removed, that rock will no longer ring. Here is a short video of me striking different rocks to hear their unique sounds.
The outer zone of the Ringing Rocks pluton is made up of two alternating mafic hybrid rock types. The early stage minerals, olivine and pyroxene, were preserved in one of the rock types but not the other, giving them quite different weathering properties. The rock that preserved them is extremely resistant to weathering and is the material that forms the tors (hill or rocky peak). The other rock is very weak and readily breaks down to a coarse soil.
The inner felsic core is a medium grained quartz monzonite that gradually turns into granite at the center.
The Ringing Rocks is a small pluton that is the deep-seated vent for a volcano that erupted 76 million years ago. The pluton is found within the Boulder Batholith. It is highly symmetrical with concentric rings of differing rock type. The inner core is made up of felsic rock while the surrounding ring is mafic.
The thin walls of the hybrid rock (caused by the mixing of the olivine basalt and granitic magmas) were eventually exposed to the surface after millions of years of uplift and erosion.
(During the Pleistocene Epoch, periglacial freezing shattered the high standing walls to form a substantial tor.)
The Ringing Rocks pluton is about a kilometer in diameter.
Ringing Rocks is roughly 20 miles East from Butte, Montana and is North of Highway I-90.
(Take Exit 241 (Pipestone) from I-90 and travel east on a gravel road (parallels interstate) for about three-fourths of a mile, then turn north on a gravel road, cross the railroad tracks and continue north for approximately 3 miles. A high clearance vehicle is recommended.)
The Boulder Batholith is located in southwestern Montana, nearby Butte and Helena, as seen in the picture above.
The Boulder Batholith is composed primarily of quartz monzonite, or adamellite. This is a felsic rock with roughly equal proportions of orthoclase and plagioclase feldspar. Granodiorite and syenogranite can also be found within the pluton and its surrounding peripheral plutons.
Originating as part of the Elkhorn Mountains Volcanics, the Boulder Batholith formed 81 to about 74 million years ago when molten magma rose up through the Earth's crust. Upon reaching the surface, it created violent explosions that hurled chucks of rocks, cinders, and volcanic ash into the air. At about 100 miles in diameter and up to 3 miles thick, the volcanic field was enormous. As the pile of volcanic rocks got too thick, magma stopped going all the way to the surface and began to accumulate near the bottom of the pile. So much magma intruded at this level that when it cooled, it formed a body of granitic rock called a batholith.
This event occurred in the late Cretaceous, during which the Farallon Plate was being subducted off the west coast of North America. The subduction and subsequent melting of this Plate created many pluton complexes in western North America, including the Idaho Batholith, Sierra Nevada Batholith, and the Boulder Batholith.
The granite that makes up the Boulder Batholith formed by the slow cooling of molten rock deep below the Earth's surface roughly 76 million years ago.
Uplift, faulting, and erosion continued over the Rocky Mountain area after the intrusion of the Boulder Batholith, which eventually exposed a large area of the batholith.
Later, faults and fractures in the Butte area cut the granite, forming pathways for hot water that carried metals in solution. As they reacted with the enclosing granite, they cooled and deposited quartz and metallic minerals to form veins.
The exposed granite in the batholith has weathered to form large boulders with rounded edges, which gives the Boulder Batholith its name.
(Discovery of copper-rich veins led to the development of both many underground mines and the city of Butte.)
The Lewis Thrust is part of the Rocky Mountains and is located within Glacier National Park in Montana, USA, Waterton Lakes National Park in Alberta, Canada, and Lewis and Clark National Forest, which is also found in Montana, USA.
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