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Chapter 8: Problem 4

Earth's interior is heated by a. angular momentum and gravity. b. radioactive decay and gravity. c. radioactive decay and tidal effects. d. angular momentum and tidal effects. e. gravity and tidal effects.

Short Answer

Expert verified
The correct answer is b. radioactive decay and gravity.

Step by step solution

01

Understanding the Earth's Interior Heating Mechanisms

The Earth's interior is heated primarily by two main processes. The first process is the decay of radioactive elements inside the Earth. The second process is the residual heat left from the Earth's formation and from gravitational contraction.
02

Identifying Radioactive Decay

The decay of radioactive isotopes, such as uranium, thorium, and potassium, releases a significant amount of heat. This process is a major contributor to the internal heat of the Earth.
03

Understanding Gravity's Role

Gravitational contraction and the energy released during the early formation of the Earth also play a role in providing heat to the planet's interior. As the Earth formed, the gravitational energy was converted into thermal energy, some of which still remains.
04

Evaluating Other Options

Considering the other options provided in the question: Angular momentum (the rotational energy of the Earth) and tidal effects (the gravitational interaction with the Moon) are not major contributors to the heating of Earth's interior compared to radioactive decay and gravitational effects.
05

Choosing the Correct Answer

Based on the explanations above, the Earth's interior is primarily heated by the processes related to radioactive decay and gravity. Therefore, the correct answer is b.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Radioactive Decay
Deep within the Earth, a natural process called radioactive decay generates a substantial amount of heat. Radioactive decay occurs when unstable isotopes of elements like uranium, thorium, and potassium break down into stable ones. This process releases energy in the form of heat, which helps warm the Earth's interior.
This heat is crucial because:
  • It drives the movement of tectonic plates
  • It creates volcanic activity
  • It causes convection currents in the mantle
This continuous generation of heat from radioactive decay has been happening for billions of years, helping to maintain the high temperatures inside our planet.
Gravitational Contraction
Gravitational contraction contributed significantly to the heating of Earth's interior during its early formation. As the proto-Earth gathered more mass, it pulled more material inward. This compression increased the planet's internal pressure and temperature.
Here's why this is important:
  • The gravitational energy was converted into thermal energy
  • This increased the overall internal heat
Even though most of the heat from gravitational contraction was generated billions of years ago, a portion of it still remains today, aiding in keeping the Earth's core hot.
Residual Heat from Earth's Formation
Not all of Earth's internal heat comes from new sources. Residual heat from the time when Earth was formed also plays a crucial role. When Earth was young, it underwent violent collisions with other celestial bodies. These impacts generated immense amounts of heat.
The reasons are:
  • Collisions created friction and generated high temperatures
  • This initial heat was trapped inside as the Earth solidified
This leftover heat has not dissipated entirely, contributing to the warmth in Earth's interior even billions of years later.

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Most popular questions from this chapter

Space missions: a. Go to the website for NASA's Messenger mission to Mercury (http://messenger.jhuapl.edu). Click on "Gallery" and then "Science Images," and look at a few of the pictures. Are the color images using real or false colors? Click on "News Center." Describe a result. b. Go to the website for the Mars Science Laboratory Curiosity (http://mars.jpl.nasa.gov/msl), which landed in 2012. What are the latest science results? c. The Google Lunar X Prize (http://googlelunarxprize.org) goes to the first privately funded team to send a robot to the Moon. The winning robot must travel some distance on the Moon's surface and send back pictures. On the website, click on "Teams" and read about a few that are still competing. What kind of people and companies are on the team? What is their plan to go to the Moon? Aside from this prize, why do they want to go to the Moon: what commercial opportunities on the Moon do they anticipate?

Citizen science: a. Go to the website for "Moon Zoo" (http://moonzoo.org), a project that lets everyone participate in the analysis of images from NASA's Lunar Reconnaissance Orbiter. Read through the FAQ, then click on "Tutorials" and select "How to Take Part." (You will need to create an account if you haven't already done so for another Zooniverse project.) In this project you count craters on the Moon, noting where there are boulders, classifying some of these features, and looking for hardware left over from exploration missions. b. Go to the website for cosmoquest (http://cosmoquest.org) and click on "Mercury Mappers." You will need to create an account for the cosmoquest projects. Click on the circled question mark under the blue check box, and read the FAQ and watch the tutorial. What is the goal of this project? Where did the data come from? Classify some images. c. Go to the website for cosmoquest (http://cosmoquest.org) and click on "Moon Mappers." As in part (b), you will need an account. Click on the circled question mark under the blue check box and read the FAQ and watch the four tutorials. What are some of the basic features? How does the angle of the sunlight and the direction of illumination affect what you see? Now classify a few craters.

Compare the kinetic energy \(\left(=\frac{1}{2} m v^{2}\right)\) of a 1 -gram piece of ice (about half the mass of a dime) entering Earth's atmosphere at a speed of \(50 \mathrm{km} / \mathrm{s}\) to that of a 2 -metric-ton SUV (mass \(=2 \times\) \(10^{3} \mathrm{kg}\) speeding down the highway at \(90 \mathrm{km} / \mathrm{h}\).

Assume that the east coast of South America and the west coast of Africa are separated by an average distance of \(4,500 \mathrm{km}\) Assume also that GPS measurements indicate that these continents are now moving apart at a rate of \(3.75 \mathrm{cm} / \mathrm{yr}\). If this rate has been constant over geological time, how long ago were these two continents joined together as part of a supercontinent?

Explain the criteria you would apply to images (assume adequate resolution) in order to distinguish between a crater formed by an impact and one formed by a volcanic eruption.
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