Transcript oceanic crust converge - UTEP :: Geological Sciences

Mountains
Chapter 9
Stress and Strain
• Stress is defined as force per unit area. It has the same units as pressure, and in fact
pressure is one special variety of stress. However, stress is a much more complex quantity
than pressure because it varies both with direction and with the surface it acts on.
• Strain is defined as the amount of deformation an object experiences compared to its original size and shape.
• Compression Stress that acts to shorten an object.
• Tension Stress that acts to lengthen an object.
• Shear Stress that acts parallel to a surface. It can cause one
object to slide over another. It also tends to deform originally
rectangular objects into parallelograms The most general definition is that
shear acts to change the angles in an object.
• Normal Stress Stress that acts perpendicular to a
surface. Can be either compressional or tensional
• Hydrostatic Stress (usually compressional) that is
uniform in all directions. A scuba diver experiences
hydrostatic stress. Stress in the earth is nearly hydrostatic.
The term for uniform stress in the earth is lithostatic.
Stress-Strain curve
Tensile Stress Test
Stress and Strain
Examples
In Geology Conditions
• Near Earths surface, Temp and Pressure are
Low
• Temperature Higher Temp.Plastic manner
• Pressure
• Time
9.1 Geologic Structures
• Fold is a bend in a rock.
Five types of Folds
Dome and Basins
Examples
Examples
Faults
Faults
Joints
• Joints a re fractures in the rock
Questions of the Day
Question ?
Question ?
Mountains
• Orogeny refers to the process of mountain Building.
In a convergent plate boundary: Folding,
faulting of rocks, earthquakes, volcanic
eruptions, intrusion of
plutons and
metamorphism.
The motor of Orogeny
is sudduction
Island Arcs
• Island Arc is volcanic mountain chain that forms where 2
plates carrying oceanic crust converge
The Andes
Himalayas
• Continent-Continent Collision
Himalayas
The
Wilson Cycle
Homework 5
Describe The Wilson Cycle
Due: Monday 4/8/13