diastrophism ko
TRANSCRIPT
DIASTROPHISM
OBJECTIVES:At the end of the presentation, you should be able to know about the following:
• Definition of Diastrophism• Theories explaining Diastrophism• Stress and Strain• Faults and Folds
Defining DIASTROPHISM:
Tectonismdeformation of Earth’s crust by natural processes (movements)
leads to the formation of continents and ocean basins, mountain systems, plateaus, rift valleys, and other features.
TRIVIA:
Do you know that?
Due to Earth’s gravity it is impossible for mountains to be higher than 49, 000 feet (15,000 metres).
THEORIES EXPLAINING DIASTROPHI
SMHow does Diastrophism occur?
1.) Isostasy Theory state of
gravitational equilibrium between the Earth's lithosphere and asthenosphere
tectonic plates "float" at an elevation which depends on their thickness and density.
Simple Analogy:
Example:
North Greenland fjord cliffs
TRIVIA: The general
term 'isostasy' was coined in 1889 by the American geologist Clarence Edward Dutton.
2.) Contraction Theory
Earth is SHRINKING.
Gravity draws the crust inward causing it to bend, buckle and trench.
Shrinking resulted in a reduction in the Earth’s diameter while the circumference remained unchanged due to folding and buckling of the crust
3.) Convection Current Theory
convection within the Earth's mantle pushes the plates
movement of a fluid, caused by differences in temperature
According to this theory:
The plate is the cooled surface layer of a convection current in upper mantle.
4.) Continental Drift Theory
Continents were joined in a super-continent, called Pangaea (all lands). Over a vast period of time, the continents drifted apart to their current locations.
Some Evidences:
The jigsaw fit of the outline of the continental margins.
Fossils
Numerous geological similarities between South America and Africa.
TRIVIA:
Continental Drift theory was first presented by Alfred Wegener who died two days after his 50th birthday.
5.) Expansion Theory Earth is physically expanding in
diameter, mass, or both.
6.) Plate Tectonics Theory Earth's outer
layer is fragmented into plates that are in constant motion.
Plate Boundaries and Their Motions
Divergent Convergen
t Transform/
Thrust
Major Earth Movements
Uplift Subsidence
TRIVIA:Do you know that?On every continent there is a city called Rome.
STRESS AND STRAIN3 main concepts about stress and strain:
rocks deform,stress causes strain and strain
results in structures,different physical conditions create
different structures
STRESS is a Force acting on some areas
3 BASIC TYPES OF STRESS
Compressional StressTensional StressShear Stress
STRESS AND STRAINStrain is a change in size, shape, or volume of a material.Response to stress
3 BASIC TYPES OF STRAIN
Elastic StrainPlastic StrainFracture Strain
NOTE :
Stress can happen with out strain, but strain cannot happen without stress.
2 Major Types of Structural Deformation
Fault Fold
Fault rocks break due to force
4 types: Normal Fault Reverse Fault Strike-Slip Fault Thrust Fault
Fold Rocks bend due to force
Types of Fold: Symmetrical Folds Assymetrical Folds Isoclinal Folds Overturned Folds Recumbant Folds Chevron Folds
REPORTED BY: CLARISSE P. CACAPIT
Syncline youngest rocks occur in the core of a
fold Caused by compressional stress U-shaped
Anticline oldest rocks occur in the core of a
fold Caused by compressional stress A-shaped
Compressional Stress two plates
move together or one moves and applies a force on another one that is not moving.
Tensional Stress
one part of a plate moves away from another part of a plate.
Shear Stress two plates
slide past one another
Elastic Strain rocks
recover to their original shape.
Plastic or Ductile Strain
Rocks do not return to their original shape.
Fracture or Brittle Strain rocks
crack or break under the stress.