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I need help on this question I need help on part A, part B, part C and part D

I need help on this question I need help on part A, part B, part C and part D

Applications and Investigations in Earth Science (9th Edition)
Applications and Investigations in Earth Science (9th Edition)
9th Edition
ISBN:9780134746241
Author:Edward J. Tarbuck, Frederick K. Lutgens, Dennis G. Tasa
Publisher:Edward J. Tarbuck, Frederick K. Lutgens, Dennis G. Tasa
Chapter1: The Study Of Minerals
Section: Chapter Questions
Problem 1LR
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I need help on this question I need help on part A, part B, part C and part D 

2. During Earth's very early history, our planet was whacked by meteorites large and small, and eventually grew to its current size. Earth probably went through a period in which it was molten from near the surface to its center. Throughout its history, Earth has been hotter at its center than at its outer surface. a. In caves just below Earth's ground surface in continental crust, the temperature tends to be a constant ~15°C (~59°F). That's why people use caves for wine storage. The deepest mine on Earth is currently the Mponeg gold mine just southwest of Johannesburg, South Africa, which reaches just over 4 km below the surface. At the bottom of that mine, the rock temperature reaches 66°C (~151°F). Using the cave temperature to represent the surface temperature of the crust at ~0 km depth, what is the rate at which temperature changes in Earth between 0 and 4 km-the near-surface geothermal gradient? C/km b. The temperature at the bottom of the lithosphere in Earth is often inferred to be around 1300°C. If we assume a depth to the base of the lithosphere of 100 km, what is a reasonable estimate for the geothermal gradient between 0 km and ~100 km? *C/km c. The center of Earth at an average depth of 6371 km below the surface has a temperature that has been estimated to be approximately 6000°C. What is the average geothermal gradient from Earth's surface to its center? C/km d. Write a brief statement of a hypothesis you think might best explain the variation in the geothermal gradient within Earth.
Transcribed Image Text:2. During Earth's very early history, our planet was whacked by meteorites large and small, and eventually grew to its current size. Earth probably went through a period in which it was molten from near the surface to its center. Throughout its history, Earth has been hotter at its center than at its outer surface. a. In caves just below Earth's ground surface in continental crust, the temperature tends to be a constant ~15°C (~59°F). That's why people use caves for wine storage. The deepest mine on Earth is currently the Mponeg gold mine just southwest of Johannesburg, South Africa, which reaches just over 4 km below the surface. At the bottom of that mine, the rock temperature reaches 66°C (~151°F). Using the cave temperature to represent the surface temperature of the crust at ~0 km depth, what is the rate at which temperature changes in Earth between 0 and 4 km-the near-surface geothermal gradient? C/km b. The temperature at the bottom of the lithosphere in Earth is often inferred to be around 1300°C. If we assume a depth to the base of the lithosphere of 100 km, what is a reasonable estimate for the geothermal gradient between 0 km and ~100 km? *C/km c. The center of Earth at an average depth of 6371 km below the surface has a temperature that has been estimated to be approximately 6000°C. What is the average geothermal gradient from Earth's surface to its center? C/km d. Write a brief statement of a hypothesis you think might best explain the variation in the geothermal gradient within Earth.
Expert Solution
Step 1

ANSWER A

 The temperature in caves just below the earth's surface is 15°C (~59°F)

At the bottom of that mine, the rock temperature reaches 66˚C (~151°F). 

The temperature difference is

Temp. Difference = 66 deg * C - 15 deg * C = 51 deg * c

As the depth required for temp. diff = 4km.

The near-surface geothermal gradient

= 514 = 12.75°C/km

ANSWER B

We have given,

temperature at bottom of the lithosphere is 1300°C

depth to the base of the lithosphere 100 km

Average Geothermal Gradient = Temp difference between top and bottom/ depth

Average Geothermal Gradient = 1300100 = 13°C/km

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