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Chapter 11
Deformation of the Crust
Section 1 Deformation of the crust
Mountain ranges are ___________________________________________.
Some of the changes are a result of deformation, or bending, tilting and
breaking of the crust.
Isostasy
It is a condition of gravitational and buoyant equilibrium between Earth’s
lithosphere and asthenosphere. Which means, ______________________;
when the crust uplifts, it will erode until a balance is reached.
Mountain and Isostasy
When mountains form they start to erode, when they erode they become
lighter making the range appear to rise. It is called _______________ due
to the isostatic adjustment.
Deposition and Isostasy
Subsidence- It is the apparent sinking of the ocean floor due to the
deposition of mud, sand and gravel flowing from rivers. This deposition is
occurring in the Gulf of Mexico at the mouth of the Mississippi River.
Glaciers and Isostasy
The weight of the ice makes the land sink the ocean floor rises because the
weight of the water is less. When the glaciers melt, the land rises and the
weight of the newly added water makes the sea floor sink.
Stress
_________________________________________________. As Isostasy
is reached, the force of an area shifts causing another area to have stress.
Compression
______________________________. Found at converging boundaries.
Tension
__________________________________. Found at divergent boundaries.
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Sheer Stress
This distorts a body by pushing parts of a body in opposite directions.
Commonly found at transform boundaries.
Strain
Any change in the shape or volume of a rock that is the result from stress.
Some stresses on a rock may not be permanent if the pressure is done
slowly and for a short time. However, longer periods of stress can lead to
physical changes.
Types of Permanent Strain
Brittle – ___________________________________________________
Ductile – __________________________________________________
Factors that Affect Strain
a. _____________________________________________________
b. _____________________________________________________
c. _____________________________________________________
Folds
A fold is when rock layers collide, the land bends up & down. It is caused by
extreme stress.
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Anatomy of a fold
Limb are the sloping sides of a fold
Hinge is where the limbs meet at the bend.
Axial plane occurs when both halves are identical.
Types of folds
Syncline - ________________________________________________
Anticline - ________________________________________________
Monocline
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Sizes of folds
The sizes of folds vary with the type and the area that has been affected.
They can be small areas, or as large as mountains.
Faults
A fault _______________________________________________________
Fracture – a break along rock that has no movement
Fault Plane – is the surface where motion occurs.
Normal Faults
____________________________________________________________
_
Reverse Faults
____________________________________________________________
_
Strike-slip fault
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____________________________________________________________
_
Sizes of faults
The sizes of the faults vary according to the area. One of the larges faults is
the San Andreas Fault.
Section 2 How mountains form
Orogeny
It is the mountain building process through the movement of the crust
or volcanism.
Many mountain ranges form this way due to extreme deformation. Mt
Everest, whose elevation is more than 8km above sea level, is the highest
mountain. Mt. St. Helen’s is a volcanic mountain that grows each year.
Mountain Ranges and systems
A mountain range is a group of adjacent mountains that are related to each
other in shape and structure.
Mt Everest is part of the Great Himalaya Range
Mt. St. Helen’s is part of the Cascade Range
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Mountain System - Is a group of mountain ranges
The Great Smoky, the Blue Ridge, the Cumberland, the Green & White
ranges make up the Appalachian Mountain Range.
Mountain Belts – The largest mountain systems joined together
Circum-Pacific belt
Eurasian-Melanesian Belt
Plate tectonics and Mountains
Both the Circum-Pacific and the Eurasian-Melanesian belts are located
along convergent plate boundaries. This is evidence that most mountains
form as a result of collision between tectonic plates.
Collisions between continental and oceanic crusts
When ocean and continental crusts collide, the ocean crust being denser will
subduct under the continental crust. This drives mountains upward. Areas
of frequent earthquakes & volcanoes because pressure is built up and
needs to be released either through eruptions and earthquakes.
Collisions between oceanic and oceanic crusts
The Mariana Islands in the North Pacific are volcanic mountains caused by
ocean to ocean collisions. One oceanic plate subducts below another. The
denser one sinks, partially melts and breaks through the crack causing an
arc of volcanic mountains.
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Collisions between two continental crusts
The leading edge of a continental crust is oceanic so when it collides with
another continental crust, it will subduct and continue to subduct until it
reaches the continental edge. Then the two continental crusts will thrust
each other upward forming mountains. The Indian plate collided with the
Eurasian one in the same manner and the result was the Himalayan
Mountains.
Types of Mountains
Folded Mountains and Plateaus
____________________________________________________________
___________________. Parts of the Alps, the Himalayas, the Appalachians
and Russia’s Ural mountains are folded.
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Plateau – the large, flat areas of rock high above sea level which were
formed when thick, horizontal layers of rock are slowly uplifted. The Tibetan
Plateau by the Himalayas and the Colorado Plateau by the Rockies.
Fault Block Mountains and Grabens
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Parts of the crust are stretched and broken into large blocks, faulting may
cause them to tilt and drop relative to other blocks. Sierra Nevada range of
California is this type of mountain.
Graben______________________________________________________
Death Valley and the Basin and Range Province of Western U.S. are
Grabens.
Dome Mountains
_________________________________________________________
They are gently sloping away from the centers.
Plutonic dome mountains1.
__________________________________________________
2.
__________________________________________________
3.
__________________________________________________
Tectonic dome mountains`
1.
__________________________________________________
2.
__________________________________________________
Volcanic Mountains
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Are mountains that form when magma erupts. They are common along
convergent plate boundaries. The Cascade Range of Washington, Oregon
and Northern California are this type of mountains, the Azores in the North
Atlantic Ocean.
Hot Spots are active areas that lie in the middle of a tectonic plate.
Hawaiian mountains are among some of the tallest in the world and are
made from hot spots; 10 km above sea level and 1160 km wide.
Tallest Mountains of the world
Mount Everest 8850m (29035 ft) Nepal
Qogir (K2) 8611m (28250 ft) India (Kashmir)
Kangchenjunga 8586m (28169 ft) Nepal
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Lhotse 8501m (27920 ft) Nepal
Makalu I 8462m (27765 ft) Nepal
Cho Oyu 8201m (26906 ft) Nepal
Dhaulagiri 8167m (26794 ft) Nepal
Manaslu I 8156m (26758 ft) Nepal
Nanga Parbat 8125m (26658 ft) Pakistan
Annapurna I 8091m (26545 ft) Nepal
TALLEST MOUNTAINS
(On Each Continent)
Mount Everest 8850m (29035 ft) Asia
Aconcagua 6959m (22831 ft) S. America
Mount McKinley 6194m (20320 ft) N. America
Mount Kilimanjaro 5963m (19563 ft) Africa
Mount Elbrus 5633m (18481 ft) Europe
Mount Willhelm 4509m (14789 ft) Oceania
Vinson Massif 4897m (16066 ft) Antarctica