Earth Science Quarter 2 - Metamorphism and Rock Deformation Notes PDF

Earth Science Quarter 2 Metamorphism and Rock Deformation  GETTING FAMILIAR WITH METAMORPHISM (4-PICS-1 WORD) Directions: Study the pictures in each set and determine the term that is being referred to by the pictures. Use the available letters...

Earth Science Quarter 2 Metamorphism and Rock Deformation  GETTING FAMILIAR WITH METAMORPHISM (4-PICS-1 WORD) Directions: Study the pictures in each set and determine the term that is being referred to by the pictures. Use the available letters and the number of boxes as clues to the word that you are going to find out.  Metamorphic rocks make up a large part of the Earth's crust and form 12% of the Earth's land surface. Some examples of metamorphic rocks are gneiss, slate, marble, schist, and quartzite. These rocks are formed through the process called metamorphism. Metamorphism is the change of minerals or geologic texture in pre-existing rocks or parent rock called protolith. In metamorphism, the protolith does not melt into liquid magma. An igneous or sedimentary rock changes to metamorphic rock because of heat, pressure, and the introduction of chemically active fluids. This occur because some minerals are stable only under certain conditions of pressure and temperature. When pressure and temperature change, chemical reactions occur to cause the minerals in Regional metamorphism is referred to as large-scale metamorphism, such as what happens to continental crust along convergent tectonic margins (where plates collide). It occurs when large areas of rocks are subjected to differential stress for long periods of time that is often associated with mountain building. Mountain building commonly occurs in subduction zones and at collision zones. The force of the collision stacked oncauses rocksso to each other, notbe onlyfolded, is there the squeezing force from broken, and but also from the weight of stacked rocks. the collision Rocks that form from regional metamorphism are likely to be foliated because of the strong directional pressure of converging  Lesson 2: Rock Deformation DIRECTIONS: Find the hidden names of geologic features that are formed by different plate boundaries that you can find in the Word Search box. The words may be traced horizontally, vertically, diagonally and backwardly. Descriptions of the different features are given under Hints. Word Search Hints: 1.It is a deep underwater valley formed when V E A C H SS T U M B an oceanic plate subducts under another O L I N N GB L O C K tectonic plate. L I S I N OE T A R O 2.These are created where two or more continental plates are pushed together. C C A K H GB U T J U 3.This is formed when new crust is created A T C S D T F A U L T under the ocean where two plates are N A S I T E P P I E U diverging. O N R G S T O R N O E 4.It is like a tear in the crust formed by two plates sliding past each other. E P D B C T D M M C S 5.These are formed from the rising magma S E generated as an oceanic plate descends into the mantle. STRESS Stress on rocks is the force applied per unit area. The force is mostly related to the movement of tectonic plates and to the weight of overlying rocks. STRAIN Strain is the resulting deformation because of stress. A strain is a change in size, shape, or volume of a material or any kind of movement of the rocks. Rocks under low confining pressures near the earth’s surface generally deform through fracturing and faulting. Rocks deep within the crust under high confining pressures deform by folding. Plate Plate Stress on rocks Strain Boundary Movement Convergen plates compressive/ ∙folding t collide compressional ∙faulting Boundary ⮚forces squeeze plates ∙stretchi Divergent move in extensive/ ng and Boundary opposite tensional thinning directions ⮚forces pull apart ∙faulting Transform plates shear ∙shearing Boundary slide past ⮚forces move ∙faulting each other past each other Stages of Rock Deformation: 1. Elastic Deformation takes place when a rock stretches but return to its original shape. 2. Ductile Deformation happens when the rock will permanently change in shape after being bent or folded. 3. Irreversible Deformation occurs when the rock will permanently change in Factors that Affect Rock Deformation 1.Confining Pressure: At high confining pressures materials are less likely to fracture because the surrounding area tends to hinder formation of fractures. 2.Temperature: At high temperature rock molecules and their bonds can move, thus, materials will behave in a more ductile manner. 3.Strength of Rock: The kind of mineral present in the rocks affect the strength of the rock. The presence of water also affects the strength of the rock. 4.Strain Rate: High strain rate materials tend to fracture while low strain rate materials tend to be ductile. FOLDING The bending of rocks when forces are applied on it at opposite directions is called folding. It is common along convergent plate boundaries and usually resulting to mountain building. Deep within the crust, as plates collide, rocks bend or crumple into folds. Once they are folded, they do not return to their original shape. Figure 6 shows the parts of rock folds. The anticline is the upfold which will begin as ridges while the syncline is the downfold which will Figure 3. Fold mountains Figure 4. Rock folds Photo credit:  FAULTING The process of causing a fracture or break in a rock due to shear stress is called faulting. This can result to earthquakes. A fracture is a simple break that does not involve significant movement of the rocks on either side. If the rocks on one or both sides of a fracture move, the fracture is called a fault. A fault is a boundary between two bodies of rock along which there has been relative motion. The San Andres fault in California corresponds to the transform boundary between twothree There are continental types plates. of faults namely normal fault, reverse fault and strike-slip fault. Normal fault is a dip-slip fault in which the block above the fault has moved downward relative to the block view. The extensional stress creates a space when two blocks of crust pull apart forming a valley. The East African Rift Zone is an example where there is normal faulting going on. Reverse fault is also known as thrust fault. It is a dip-slip fault in which the upper block, above the fault plane, moves up and over the lower block. The vertical movement of the crustal blocks is due to compressional stress. This type of fault commonly takes place in convergent boundaries like that in the Himalayas and Rocky Mountains. A strike slip fault, on the other hand, is due to the shearing or the sliding of rocks. The Philippine Fault Zone (PFZ)is an example of a strike slip fault which is 1,200 km-long and stretches from northwestern Luzon to southeastern Mindanao. Below shows the comparative behavior of faults.