Sedimentary Rocks - Lab Report Example

Sedimentary Rocks Start your Lab Assignment by responding to the Big Question, What a sedimentary rock can tell you about the environment in which it formed. Use your own words to fill in the blank. (In Sentences) “Based on my prior knowledge of petrology, a component of geology The Features of a sedimentary rock, such as composition and texture tell me conditions about past environments. I know this because sedimentary rocks are formed from pre-existing rocks and once living organisms” 2. Your Thoughts: With the Big Question in mind, “What can a sedimentary rock tell you about the environment in which it formed?” what are your thoughts about how sedimentary rocks form I think sedimentary rocks form when fragments from other rocks, minerals or organisms are accumulated and cemented or when organic growths occur in water through sedimentation because rocks exhibit characteristics and features of their past environments. 3. A.II.3 Your Thoughts: In your Lab Assignment, describe your thoughts about why weathering, erosion and deposition would be important concepts to understand when discussing sedimentary rocks? I think weathering, erosion, and deposition are important because… Example: Shoreline. Description of the agent: Flowing Water-as the ocean waves strike the beach the waves cause sediment to move back and forth. When the waves are strong, the sediment is transported and when the waves are weak the sediment is deposited. This is how beaches are formed and eroded. Appearance of the Sediment after Deposition (sorted or unsorted, notes about the appearance such as angular or rounded clasts, and an explanation of why) The sediment appears...sorted with rounded clasts… because …, in environments where the long shore current is strong sediment, mostly sand to silt close to shore, are eroded and transported. When the long shore currents meet a change in direction the velocity of the current slows and sediment is deposited. The long distance of transport and back and forth movement of the waves knocks the corners off of the clasts causing them to be rounded. Follow the example above to answer the following questions: (In sentences) Mountainous, Glaciers move because of the pressure exerted by their weight because of gravity. The bottom half of the glacier rubs against the mountain rock breaking them as it moves down slope. Some of the sediments are carried within the glacier and deposited down. The sediments appear sorted and angularly clasts because smaller sediments are transported far away and larger ones are deposited closer to the mountain. Mountainous, Mass-wasting- loosely placed rocks and soil move downhill under the influence of gravity. The carried material rub against the rocks on the hill surface breaking them into smaller fragments as they are deposited downhill. The sediments appear angular because they rub against each other down slope constantly breaking. The sediments are sorted in their deposition because of gravitational move. Mountainous, Running Water- as running water moves down the mountain it carries with it sediments of rocks which rub against the mountain surface breaking them into smaller fragments before being deposited downhill. The sediment appears rounded because of the constant shaping by the flowing water and are deposited in sorted manner depending on their densities. River Channel, Running water moves down the stream carrying with it sediments of rocks which rub against the river bed breaking them into smaller fragments before being deposited downstream. The sediments appears rounded shaped because of washing by flowing water eliminating the angular edges. The deposition sorted since it is dependent on the weight of the rocks. Fold plain, Running Water flows down bearing debris of sediments which collide and break down into smaller pieces. The sediments are deposited on the river bed as the water velocity reduces because change in slope. The sediment appears rounded shaped and sorted because their deposition is based on density of the rock fragments. Desert Environment, Wind blows carrying with it sediments which rub against the desert features. As the pieces move they break into small sediments which are later deposited when the wind looses its energy. The sediments are angularly shaped because of the streamlined effect caused by the wind. The deposition is sorted because it depends on wind velocity and weight of the sediments. Desert Environment, as rocks in the desert loose heat during evaporation, cracks remain which crumble and eventually disintegrates. The deposited sediments appear angular in shape because the disintegration process is caused by alternating expansion and contraction causing fault lines along the rocks. The deposition is unsorted. A.II.3 Your Thoughts: In your Lab Assignment, describe your thoughts about why weathering, erosion and deposition would be important concepts to understand when discussing sedimentary rocks? I think weathering, erosion, and deposition are important because the processes they are crucial in the formation of sedimentary rocks and influence the composition and texture of the rocks. Weathering is different than erosion because weathering is the breaking down of rocks while erosion is the moving them from one point to another. Your Thoughts: With the Big Question in mind, “What can a sedimentary rock tell you about the environment in which it formed?” finish the following statements in your Lab Assignment I think it is important to learn about sedimentary rocks and the environments in which they form because they represent their environment of formation. Furthermore, I would need to learn more about weathering, erosion and deposition to better understand the formation of sedimentary rocks. A.IV.1 Use the knowledge that you have developed in this laboratory to answer the following questions. (in sentences) Using a hammer to break a rock sample into small fragments will increase the rate of chemical weathering because it increases the area exposed to chemical agents. Coal cannot be a mineral because it is inorganically formed however, it is clearly a sedimentary rock because it is made of decomposed inorganic plants. In examining an unknown rock sample, it would be important to test chemical composition to determine if it was a sedimentary rock this test works because it reflects the chemical composition of the parent rock. 2 Sedimentary rocks have a number of practical uses. Use the knowledge you have gained in this laboratory to answer the following questions. Be sure to make reference to properties that you observed for these specific samples Of the rock samples examined in this laboratory, I think that flagstone would be the best to crush for landscape rock because of its angular flat shapes. Of the rock samples examined in this laboratory, I think that sandstone would be the best to polish for decorative purposes because of their aesthetic appearance. Of the rock samples examined in this laboratory, I think that limestone would be cause the most problems for construction (e.g. Building tunnel, etc) because it wears off to erosion agents easily. Now that you have heard what others think about “What can a sedimentary rock tell you about the environment in which it formed?” revisit your ideas and modify them to reflect your current understanding. (Be sure to use your experience in this lesson and the evidence you collected to support your claims). Based on my prior knowledge of petrology, the features of a sedimentary rock, such as texture and composition, tell me conditions about past environments. I know this because they are formed from disintegration of other rocks. My original ideals have not changed in that it is consistent with the results of the lab report. My ideas are similar to others because of the consistency in the way sedimentary rocks are formed. Work Cited Oxlade, Chris. Sedimentary Rocks. Chicago: Heinemann Library, 2011. Print. Read More