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Stress, Faulting, Folding, Mountain Building. Inside Earth:. Have you ever tried to bend something, only to have it break?. How can material bend at one time and break at another?. The answer is that the stress you put on the material was different each time. - PowerPoint PPT Presentation
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Stress, Faulting, Folding, Mountain BuildingInside Earth:
•Have you ever tried to bend something, only to have it break?
How can material bend at one time and break at another?• The answer is that the stress you put on the material was different each time.
• Stress is the amount of force per unit area on a given material.
This same principle applies to the rocks in the Earth’s crust• Different things happen to rock when different
types of stress are applied.
Deformation• Deformation is the process
by which a rock changes because of stress.
• Rock layers bend when stress is placed on them.
• When enough stress is placed on rocks, they reach their elastic limit and break.
• There are two kinds of stress:• Compression• Tension
Compression• This type of stress
occurs when an object is squeezed.• Tectonic plates collide
• When compression happens at a convergent boundary, large mountain ranges can form
Tension• Another form of
stress is tension.• Tension is the stress
that occurs when forces stretch an object.
• They occur at divergent boundaries.•Mid Ocean ridges
Folding• The bending of rock layers because of stress in
the Earth’s crust is called folding.
• Scientists assume that all rock layers started as horizontal layers.
• When they see folding, they know that deformation has occurred
• There are three types of folding: anticlines, synclines and monoclines
• http://www.youtube.com/watch?v=jVyBsUgD7Gk&safety_mode=true&persist_safety_mode=1
Anticlines• Upward arching
folds
Synclines• Down-ward, trough-
like folds
Monoclines• Rock layers are
folded so that both ends of the fold are horizontal.
Faulting• Some rock layers break when stress is
applied to them.• The surface along which rocks break and
slide past each other is called a fault.• The blocks of crust one each side of the
fault is called a fault-block.
Not all faults are vertical…• And understanding the
difference between it’s two sides, called hanging walls and foot walls is useful.
• The type of fault that forms depends on how the hanging wall and foot wall move in relationship to each other.
Normal Faults• When a normal
fault moves, it causes the hanging wall to move down relative to the footwall.
• Normal faults usually occur when tectonic forces cause tension that pull rocks apart
Reverse Faults• When a reverse
fault moves, it cause the hanging wall to move up relative to the footwall.
• Usually happen when tectonic forces cause compression that pushes rocks together
Strike-Slip Faults• The third type of
fault is called a strike-slip fault
• These form when opposing forces cause rock to break and move horizontally.
• The San Andreas fault is a strike-slip fault
Plate Tectonics and Mountain Building• http://www.youtube.com/watch?v=jqEo6nnSvhM&safety_mode=true&persist_safety_mode=1
• When tectonic plates collide, land features that start as faults and folds can eventually become large mountain ranges.
Mountains exist because tectonic plates are constantly moving around• As a result of this movement, they collide with
each other.
• Mountains, such as the Andes Mountains in South America, form in the subduction zone where two tectonic plates converge.
Mountains are formed in several ways• The three most common types of
mountains are classified by the way they were formed
•Folded Mountains
•Fault-Block Mountains
•Volcanic Mountains
Folded Mountains• Formed at the
convergent boundaries where the continents have collided.
• Formed when rock layers are squeezed together and pushed upward.
• The highest mountain ranges in the world• Appalachians• Himalayas
Fault-Block Mountains• Form when tension
pulls on large blocks of the Earth’s crust to drop down relative to other blocks.
• Sharp, jagged peaks
• Grand Tetons in Wyoming
Volcanic Mountains• Most of the world’s major
volcanic mountains are located at convergent boundaries.• Ring of Fire!
• They form when magma rises to the Earth’s surface and erupts, forming a volcanic mountains.
• Can also be found underwater
Uplift and Subsidence• Vertical movements in the Earth’s crust are
divided into two types.
• Uplift: created by the rising of the Earth’s crust to higher elevations
• Subsidence: The sinking of the Earth’s crust to low.er elevations
Compression Th