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ROCKY MOUNTAIN SYSTEM
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GEOGRAPHICAL LOCATION:• The Rocky Mountains, often called the Rockies, are a
mountain range in western North America
• The Rocky Mountains stretch more than 3000 miles
from northern most British Columbia,in Canada,to
New Mexico in the United States.
• Highest peak-Mount Elbert in Colorado(14,440 ft
above sea level).
Geological Events:• Geology of the Rocky Mountains reveals a
discontinuous series of mountain ranges with distinct
geological origins
• The Rocky Mountains took shape during a period of
intense plate tectonic activity that formed much of
the rugged landscape of the western United states.
• Three major mountain-building episodes reshaped
the west from about 170 to 40 million years ago iods.
• The Laramide orogeny, about 70–40 million years
ago, was the last of the three episodes and was
responsible for raising the Rocky Mountains
Raising the Rockies :• The growth of the Rocky Mountains has been one of
the most perplexing of geologic puzzles.
• Mountain building is normally focused between 200
to 400 miles inland from a subduction zone
boundary. Geologists continue to gather evidence to
explain the rise of the Rockies so much farther
inland; the answer most likely lies with an unusual
subducting slab.
• At a typical subduction zone, an oceanic plate
typically sinks at a fairly high angle, and a volcanic arc
grows above the subducting plate.
Raising the Rockies(continuation)...............
• It is postulated that the shallow angle of the subducting plate
greatly increased the friction and other interactions with the
thick continental mass above it. Tremendous thrusts piled
sheets of crust on top of each other, building the
extraordinarily broad, high Rocky Mountain range
• The current Rockies were forced upwards through the layers
of Pennsylvanian and Permian sedimentary remnants of the
Ancestral Rocky Mountains. Such sedimentary remnants were
often tilted at steep angles along the flanks of the modern
range and visible in many places throughout the Rockies,
included prominently along the Dakota Hogback, an early
Cretaceous sandstone formation that runs along the eastern
flank of the modern Rockies.
The Rocks that Make Up the Rockies :• The Rockies are composed exclusively of layered
sedimentary rocks. These include
limestone,dolomite,sandstone and shale.
• There are also a few isolated pockets of igneous
(formerly molten) rocks.
• Sedimentary rocks have a unique method of
deposition – one layer on top of another. Digging
through the layers, geologists can analyze their
composition, and determine much about the climate
and landscape during the time of their formation.
Composition of sedimentary rocks:• Sedimentary rocks in rockies can be divided into two
major groupings: inorganic and organic.
• Inorganic rocks are those formed by the deposition
of inorganic matter. This includes minerals as well as
the remains of other older rocks that were eroded
away, only to have their individual grains deposit as
layered sediments.
• Organic rocks are further broken down into chemical
and organic origins. This group combines rocks
formed from the remains of living organisms along
with rocks resulting from several chemical processes.
These include the limestones and dolomites that
form many of our mountain summits, along with
other valuable resources like coal.