Lecture 3 Stress And Strain Flashcards
(15 cards)
What is glaciotectonic?
Deformation of sediments and bedrock at the toe of an advancing ice sheet
This process occurs as ice sheets move and exert pressure on the underlying materials.
Define salt tectonics.
Deformation mostly by the vertical movement of salt through its overburden
Salt tectonics involves the movement of salt layers beneath the Earth’s surface, affecting the geological structures above.
What does neotectonics study?
Ongoing crust motion and the contemporaneous stress field
Neotectonics focuses on recent geological processes and their impact on the Earth’s crust.
What is the difference between stress and strain?
Stress causes distortion; strain is the observable and measurable distortion of the original structures
Stress refers to the forces applied to a material, while strain is the result of those forces.
What primarily drives glaciotectonics and salt tectonics?
Gravity and plate tectonics
These forces play a crucial role in the deformation processes associated with glaciotectonics and salt tectonics.
What does strain involve in the context of deformation?
Displacement, strain, and changes in shape
Strain can be described in terms of how particles in rocks change position relative to each other.
Fill in the blank: Strain is A_______ / A_______ / A_______ of rocks and structures.
length / shape / size
These dimensions help in understanding how rocks deform under stress.
What are the two types of deformation mentioned?
Homogeneous and heterogeneous deformation
Homogeneous deformation maintains the volume of the material, while heterogeneous deformation does not.
What does one-dimensional strain involve?
Stretching and shortening of lines or approximately linear objects
This type of strain is often measured in terms of elongation or contraction.
What is the equation for elongation in one-dimensional strain?
e = (l_after - l_before) / l_before
This equation calculates the change in length relative to the original length.
True or False: Negative extension indicates contraction.
True
Negative extension occurs when the length of an object decreases.
What is shear strain?
y = tan(W), where W is the angle between two originally perpendicular lines in a deformed medium
Shear strain quantifies the distortion of a material due to shear stress.
What characterizes three-dimensional strain?
Uniform extension, uniform flattening, and plane strain
These concepts describe how materials deform in three dimensions under varying conditions.
What is uniform extension?
Axially symmetric extension/constriction
This type of strain occurs when an object is stretched uniformly in all directions.
What is plane strain?
Stretching in one direction and shortening in a single perpendicular direction
In plane strain, there is no stretching or shortening in the third principal direction.
