#811 T-Mobile . 9:49 AM Graded Activities-Metamorp Unit 2: Rocks & Minerals WS:
ID: 290029 • Letter: #
Question
#811 T-Mobile . 9:49 AM Graded Activities-Metamorp Unit 2: Rocks & Minerals WS: Metamorphic Rocks Name: Use the table below to help you understand and answer questions about the changes in rocks caused by heat and pressure. Temperature (deg C) 200 30 mentary: no etamorphis Contact Metamorphism Km Grade Partial Slate melting. Regional Blueschist Igncous High Gradepocesses Conditions rarely found 30-in carth's Gneiss lithosphere 1. What is the relationship between rock temperature and depth beneath the surface? 2. Which metamorphic rock shown forms at the highest temperature? 3. Through what general temperature range would you expect schist to form? 4. How man y killometers beneath the surface does gneiss occur? 5. What is the approximate temperature at a depth of 20 km? F:0ocumentsiEarScience!Unt 2 RockalMetamorphic Rocks Worksheetdoe Dashboard Calendar To Do Notifications InboxExplanation / Answer
1. The relationship between temperature and depth is well very well understood by the diagram as that with the increase in depth, gradually the temperature also increases. The temperature must increase in order to maintain the thermodynamic equilibrium. Thus is because of the change in another extensive property inside the earth, which is pressure. Hence, with every increase in depth, temperature and pressure also increases.
2. The rock which is formed at highest temperature according to the graph is Pyroxene-hornfels(usually associated with the rocks involved with contact metamorphism).
3. Schists appears after the pressure and temperature exceeds the region for slates. Therefore the temperature range at which the schists can form is 270 to 4000C.
4. Gneissic rocks are the highest grade of rocks which form after the temperature and pressure exceeds the region of schists. Therefore the depth of about 30 to 34 kms inside the earth, gneiss can form.
5. The temperature at certain depth inside the earth can be found out by the determination of the thermal gradient at that depth. In general, the thermal gradient increases with 250 per kms. So the general temperature at 20 kms= 20x25 = 5000C.
6. The depth at which shale generally metamorphoses to slate is 13 to 17 kms inside the earth.
7. Metasomatism is usually decribed as one of the processes involving isochemical change in the rocks due to the involvement of the water into the rock by the virtue of the occurence of fracture and cleavages. Hence, the changes generally takes place where the solidus in granite is reached. This is because solidus is the temperature at which the first liquid generally appears.
Therefore the temperature at which the granite starts melting is 650oC. Hence metasomatism (according to the graph provided) starts at this temperature.
a) Partial melting of granite can occur in the depths increasing from 6 to 36 kms inside the earth. It all depends upon under what conditions(pressure and depth) the temperature has been reached.
b) Inside the earth temperature exceeding 700oC may attain by the involvement of fluids in the rocks which lowers down the solidus and thus can trigger the process of partial melting. At high level of water saturation or any fluid availability these situation might arise.
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.