movement of plates and formation of folds and faults
- 1. MOVEMENT OF PLATES and FORMATION OF FOLDS AND FAULTS
- 2. Learning Competency • Explain how the movement of plates leads to the formation of folds and faults
- 4. Plates Movement • Rocks that were originally deposited in horizontal layers can subsequently deform by tectonic forces into folds and faults.
- 5. Plates Movement • Folds constitute the twists and bends in rocks. Faults are planes of detachment resulting when rocks on either side of the displacement slip past one another.
- 7. Plates Movement • The movement of the plates depends on the boundaries between them. These boundaries can be convergent, divergent, or transform.
- 9. • Earth’s surface is composed of tectonic plates that are constantly moving. • Tectonic plates experience different types of forces; tension and compression
- 10. • Tension occurs when the plates are pulled apart causing either an elongation or a breakage in the crust. • Volcanic islands, and mid- oceanic ridges are formed
- 11. • Compression occurs when the plates are pushed toward each other causing them to crash. • Mountains are formed due to compression
- 12. • Folding occurs when the Earth’s crust bends away from a flat surface. • Anticline-upward bend • Syncline- Downward bend
- 13. • Faulting happens when the Earth’s crust completely breaks and slides past each other. • Causes earthquakes to occur.
- 14. 1. CONVERGENT- 2 plates move toward each other; Oceanic-oceanic oceanic-continental • Subduction- denser sinks over the other. • Formation of Trenches and Volcanoes PLATE BOUNDARIES
- 15. 2. DIVERGENT- 2 plates move away from each other; magma rises forming new land - older rocks are pushed aside - Formation of RIDGES PLATE BOUNDARIES
- 16. 3. TRANSFORM-FAULT- when plates move slide past each other; two plates move/ slide in opposite direction -Formation of faults PLATE BOUNDARIES
- 17. 1. Divergent plate boundaries – two plates move away from each other. Places where plates are coming apart are called divergent boundaries. 2. Covergent plate boundaries – two plates move towards each other. Mountains, earthquake, and volcanoes form where plates collide. Types of Plate Boundaries
- 18. 3. Transform plate boundaries – two plates slip past each other. Places where plates slide past each other called transform boundaries. The sliding motion causes earthquakes.
- 19. Plates Movement • Plate movements cause rocks to be deformed due to compressional stress at convergent boundaries, tensional stress at divergent boundaries, or shear stress at transform boundaries. Due to these stresses, rocks experience changes in volume and shape.
- 20. There are basically 3 types of tectonic forces that can deform rocks. • The type of strain (deformation) that develops in a rock depends on the tectonic force. a. Compressive forces squeeze and shorten a body. b. Tensional forces stretch a body and pulls it apart c. Shearing forces push different parts of a body in opposite directions When subjected to stress, rocks can deform by either breaking (fracture) or bending (fold).
- 22. Fracture • Since the pressure and temperature are low at the Earth’s surface, rocks tend to break or fracture when subjected to compressional and tensional stresses.
- 23. Plates Movement • Fractures can either be a fault or a joint. A fault is a break in the rock where there is considerable movement on the fracture surface while a joint is a break where there is no considerable movement.
- 24. Types of Fault •There are two types of faults. They can either be dip-slip or strike- slip faults.
- 25. Types of Fault • Dip-slip faults involve the vertical movement of the blocks of rock. These movements are described based on the direction of the motion of the hanging wall with respect to the footwall.
- 26. Types of Fault • Dip-slip faults can either be a normal or a reverse fault. A normal fault is caused by tensional stress. A reverse fault, wherein the hanging wall moves upward, is formed by compressional stress.
- 28. Types of Fault • Strike-slip fault involves a horizontal movement of blocks of rock and is caused by shear stress.
- 30. Fold • Deep within the crust, where pressure and temperature are high, rocks are plastic-like; thus, they do not break but they tend to bend or fold. When rocks in this area are compressed, they become thicker. When rocks become thinner, they are pulled apart.
- 31. • When blocks of rock are bent upwards, they form anticline structures. Synclines are formed when blocks of rock bend downwards. A slightly bent rock from the parallel undeformed layers forms monoclines.
- 32. Types of Fold 1. Anticline is a fold that is convex up and has its oldest beds at its core.
- 33. Types of Fold 2. Syncline is a fold with younger layers closer to the center of the structure.
- 34. Types of Fold 3. Monocline is a local warping in horizontal strata. Rock beds lying at two level separated by steep inclined limbs.