Download Unit 4 Chapter 11

Unit 4 Chapter 11
Deformation of the Crust
Section 1 Deformation of the crust
Mountain ranges are a visible reminder
that the Earth is constantly changing.
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, Earth stays
in balance; 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
uplift 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
Stress is the amount of energy exerted on an area. As Isostasy is
reached, the force of an area shifts causing another area to have
stress.
Compression
Squeezes and shortens the rock. Found at converging
boundaries.
Tension
Stretches and pulls the body apart. Found at divergent
boundaries.
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 – breaking or fracturing
Ductile – bending or deforming
Factors that Affect Strain
The composition of the rock
The temperature or pressure
The types of stress or the length of time
Folds
A fold is when rock layers collide, the land bends up &
down. It is caused by extreme stress.
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.
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.
Syncline - downward fold of rock
Anticline - uplifted area of rock
Monocline
Faults
A fault is a crack in the earth where movement has occurred.
Fracture – a break along rock that has no movement
Fault Plane – is the surface where motion occurs.
Sizes of faults
The sizes of the faults vary according to the area. One of the larges
faults is the San Andreas Fault.
Normal Faults
One side of the land moves downward relative to the other
side
Reverse Faults
When one side of the land moves upward relative to the
land around it
Strike-slip fault
When rock on each side of the fault move horizontally past
each other
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
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.
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
When tectonic movement squeezes rock layers together like an
accordion-like fold. Parts of the Alps, the Himalayas, the
Appalachians and Russia’s Ural mountains are folded.
Plateau
They are 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 are plateau.
Fault Block Mountains and Grabens
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- a long narrow valley usually found opposite a fault block
mountain.
Death Valley and the Basin and Range Province of Western U.S.
are Grabens.
Dome Mountains
They are circular folded mountains resulting from uplifting forces
(magma). They are gently sloping away from the centers.
Plutonic dome mountains1. Result of underground volcanism
2. Rock layers are pushed up because of an igneous intrusion
3. Colorado Plateau, Rocky Mountains, Henry Mountains (Utah)
Tectonic dome mountains` 1. Resulting from uplifting forces
2. Adirondack Mountains, Black Hills of S. Dakota
Volcanic Mountains
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 Spot
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
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Mount Everest 8850m (29035 ft) Nepal
Qogir (K2) 8611m (28250 ft) India (Kashmir)
Kangchenjunga 8586m (28169 ft) Nepal
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