Stress in the earth’s crust

Earth Science report

1. Stress in the Earth’s Crust By: Egee F. Firmalo

2. Objectives List different types of tresses that cause different type of deformation Compare the different types of folds and the conditions under which they form. Compare fractures and faults and define how are they related to earthquakes. Compare how mountains form and at what types of plate boundaries.

3. What causes rocks deformation? Rocks are solid, but will respond when force are applied to them. When rock deformation is being discussed the term stress is used rather than pressure.

4. What is a stress? Stress  is the force applied to a rock . In Geology stress is the force per unit area that is placed on a rock.

5. Types of Stress Confining stress Compression   stress Tension   stress Shear   stress

6. Confining stress Confining stress  happens as weight of all the overlying rock pushes down on a deeply buried rock. The rock is being pushed in from all sides, which compresses it.

7. Compression  stress Compression  stress squeezes rocks together. Compression causes rocks to fold or fracture. Compression is the most common stress at convergent plate boundaries.

8. Tension stress Tension stress pulls rocks apart. Tension causes rocks to lengthen or break apart. Tension is the major type of stress found at divergent plate boundaries.

9. Shear stress Shear  stress happens when forces slide past each other in opposite directions. This is the most common stress found at transform plate boundaries.

10. Compression Stress Tension Stress Shear Stress

11. Folds When rocks are experiencing stress deform plastically, the rock crumple into folds. When a rock bends without breaking, it folds.. Folds are made up when two plates the earth’s crust collide.

12. three types of folds Monoclines Anticlines Synclines

13. monocline   A monocline  is a simple “one step“ bend in the rock layers. In a monocline, the oldest rocks are still at the bottom and the youngest are at the top .

14. anticline An anticline is a fold that arches upward. The rocks dip away from the center of the fold. The oldest rocks are found at the center of an anticline. The youngest rocks are draped over them at the top of the structure.

15. When upward folding rocks form a circular structure, that structure is called a dome. If the top of the dome is eroded off, the oldest rocks are exposed at the center.

16. syncline A syncline is a fold that bends downward. In a syncline, the youngest rocks are at the center. The oldest rocks are at the outside edges. When rocks bend downward in a circular structure, it is called a basin.

17. Fracture Fractures are among the most common of all geologic features . A crack or a fault in a rock.

18. Faults The place where movement occurs along plate boundary . Faults are fractures in Earth's crust where rocks on either side of the crack have slid past each other . Fault are cracks in earth’s crust where movement occurs on at least one side .

19. Parts of a fault Hanging Wall Foot wall

20. Types of Fault Normal fault Reverse Fault Strike Slip Faults

21. Normal fault Normal fault create space . Two blocks of crust pull apart, stretching the crust into a valley.

22. Reverse faults Reverse faults , also called thrust faults, slide one block of crust on top of another . These faults are commonly found in collisions zones, where tectonic plates push up mountain ranges such as the Himalayas and the Rocky Mountains.

23. Strike-slip faults Strike-slip faults indicate rocks are sliding past each other horizontally, with little to no vertical movement. Both the San Andreas and Anatolian Faults are strike-slip.

24. Mountains Mountains are magnificent and inspiring features. Just thinking of mountains conjures up beautiful images of places like the Rockies, the Andes, Hawaii and the Alps. But not all mountains are the same. Though they all take a very long time to form, mountains are created in different ways depending on where they are on Earth. Some mountains are created by land pushing together, while others are formed over hotspots on Earth.

25. Tectonic Plates

26. Plate Boundaries As plates interact, a boundary between these plates exist or locations where two tectonic plates meet.

27. Three types of plate boundaries Divergent boundary Convergent boundary Transform plate boundary

28. Divergent Boundary A  divergent boundary  occurs when two tectonic plates move away from each other . This most often takes place at ocean ridges. Volcanic activity is the most common seen in a divergent boundary As the plates separate from each other new crust is being made.

29. African rift valley

30. Convergent Boundary When two plates come together, it is known as a  convergent boundary .  Convergent plate boundaries are locations where lithospheric plates are moving towards one another. The impact of the two colliding plates buckles the edge of one or both plates up into a rugged mountain range, and sometimes bends the other down into a deep seafloor trench.

31. Transform plate boundaries Two plates sliding past each other forms a  transform plate boundary . A boundary were plates are slide past each other. At this type of boundary the only effect is the earth quake .

32. Plate Boundaries Type of Stress Kind of Deformation Types of that deformation Example Divergent Boundary Tensional Stress Fracture Fault (normal fault) West Africa rift Valley Convergent Boundary Compressional Stress Fold Fracture (It can be any type of fold) Fault (Reverse Fault) Himalayan Mountain Andes Mountain Transform plate boundaries Shear stress Fracture Fault (Strike Slip Fault) San Andrea’s Fault

33. By Henry David Thoreau “You must love the crust of the earth on which you dwell more than the sweet crust of any bread or cake. You must be able to extract nutriment out of a sand-heap. You must have so good an appetite as this, else you will live in vain.”