Summary earth portrait of a planet 7th edition 2022 stephen marshak chapters 1 - 13
, Summary earth portrait of a planet 7th edition 2022 stephen marshak chapters 1 - 13
Contents
Chapter 1: An Evolving Image of the Earth’s Position and Shape....................................................................................5
1.2 A Sense of Scale.....................................................................................................................................................5
1.3 The Modern Image of the Universe.......................................................................................................................5
1.4 How Did the Universe Form?.................................................................................................................................5
1.5 Making Order from Chaos......................................................................................................................................5
1.6 We Are All Made of Stardust..................................................................................................................................6
Chapter 2: Journey to the Center of the Earth.................................................................................................................6
2.1 Introduction...........................................................................................................................................................6
2.3 The Atmosphere....................................................................................................................................................6
2.4 Land and Oceans....................................................................................................................................................7
2.5 What is the Earth made of?...................................................................................................................................7
2.6 How do we know that the Earth had layers?.........................................................................................................7
2.7 What are the layers made of?................................................................................................................................7
2.8 The Lithosphere and Asthenosphere.....................................................................................................................8
Chapter 3: Drifting Continents and Spreading Seas.........................................................................................................8
3.1 Introduction...........................................................................................................................................................8
3.2 What was Wegener’s evidence for continental drift?............................................................................................8
3.3 Setting the stage for the discovery of sea-floor spreading.....................................................................................8
3.4 Harry Hess and his “Essay in Geopoetry”...............................................................................................................9
3.5 Marine magnetic anomalies: Evidence for sea-floor spreading.............................................................................9
3.6 Deep-sea drilling: Further evidence.......................................................................................................................9
Chapter 4: The Way the Earth Works: Plate Tectonics...................................................................................................10
4.1 Introduction.........................................................................................................................................................10
4.3 Divergent plate boundaries and sea-floor spreading...........................................................................................10
4.4 Convergent plate boundaries and subduction.....................................................................................................10
4.5 Transform plate boundaries.................................................................................................................................10
4.6 Special locations in the plate mosaic...................................................................................................................11
4.7 How do plate boundaries form and die?..............................................................................................................11
4.8 What drives plate motion?...................................................................................................................................11
Chapter 5: Patterns in Nature: Minerals........................................................................................................................11
5.1 Introduction.........................................................................................................................................................11
5.3 Beauty in Patterns: Chemicals and Their Structure..............................................................................................12
5.4 How Can You Tell One Mineral from Another......................................................................................................12
5.5 Organize Our Knowledge: Mineral Classification.................................................................................................12
5.6 Something Precious: Gems!.................................................................................................................................13
Chapter 6: Up From the Inferno: Magma and Igneous Rocks........................................................................................13
6.1 Introduction.........................................................................................................................................................13
6.2 Why does magma form?......................................................................................................................................13
6.3 What is magma made of?....................................................................................................................................13
, Summary earth portrait of a planet 7th edition 2022 stephen marshak chapters 1 - 13
6.4 Moving magma and lava......................................................................................................................................13
6.5 How do extrusive and intrusive environments differ...........................................................................................14
6.6 Transforming magma into rock............................................................................................................................14
6.7 Igneous rock textures: what do they tell us?.......................................................................................................14
6.8 Classifying igneous rocks......................................................................................................................................14
Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks........................................................................15
7.1 Introduction.........................................................................................................................................................15
7.2 How does weathering lead to sediment formation?............................................................................................15
7.3 Soil: Sediment Interwoven with Life....................................................................................................................15
7.9 How Do We Recognize Depositional Environments?...........................................................................................17
7.10 Sedimentary Basins............................................................................................................................................17
7.11 Diagenesis..........................................................................................................................................................17
Chapter 8: Metamorphism: A Process of Change..........................................................................................................17
8.1 Introduction.........................................................................................................................................................17
8.2 What Happens During Metamorphism?..............................................................................................................17
8.3 What Causes Metamorphism?.............................................................................................................................17
8.4 How Do We Classify Metamorphic Rocks?...........................................................................................................18
8.5 Describing the Intensity of Metamorphism.........................................................................................................18
8.6 Where Does Metamorphism Occur?....................................................................................................................18
8.7 Where Do You Find Metamorphic Rocks?............................................................................................................19
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions.....................................................................................................19
9.1 Introduction.........................................................................................................................................................19
9.3 The Architecture and Shape of Volcanoes...........................................................................................................20
9.4 Eruptive Styles: Will It Flow, or Will It Blow?........................................................................................................20
9.5 Hot-Spot Eruptions...............................................................................................................................................20
9.6 Eruptions along Plate Boundaries and Rifts.........................................................................................................21
9.8 Protection from Vulcan’s Wrath..........................................................................................................................21
9.9 The Effect of Volcanoes on Climate and Civilization.............................................................................................21
9.10 Volcanoes on Other Planets...............................................................................................................................21
Chapter 10: A Violent Pulse: Earthquakes......................................................................................................................21
10.1 Introduction.......................................................................................................................................................21
10.2 What Causes Earthquakes to Happen?..............................................................................................................21
10.3 How does Earthquake Energy Travel?................................................................................................................22
10.4 How Do We Measure and Locate Earthquakes?................................................................................................22
10.5 Where and Why Do Earthquakes Occur?...........................................................................................................23
10.6 How Do Earthquakes Cause Damage?...............................................................................................................23
10.7 Can We Predict the “Big One”?..........................................................................................................................23
10.8 Earthquake Engineering and Zoning..................................................................................................................24
Chapter 11: Crags, Cracks, and Crumples: Crustal Deformation and Mountain Building...............................................24
11.1 Introduction’......................................................................................................................................................24
11.3 Rock Deformation in the Earth’s Crust...............................................................................................................24
, Summary earth portrait of a planet 7th edition 2022 stephen marshak chapters 1 - 13
11.4 What Structures From During Brittle Deformation?..........................................................................................24
11.5 What Structures From Due to Ductile Deformation?.........................................................................................25
11.6 Igneous, Sedimentary and Metamorphic Processes in Orogenic Belts..............................................................25
11.8 Causes of Mountain Building.............................................................................................................................26
11.9 Cratons and the Deformation within Them.......................................................................................................26
11.10 Life Story of a Mountain Range: A Case Study.................................................................................................26
Chapter 12: Deep Time: How Old Is Old?.......................................................................................................................26
12.1 Introduction.......................................................................................................................................................26
12.2 Time: A Human Obsession.................................................................................................................................27
12.4 Principles for Defining Relative Age...................................................................................................................27
12.5 Unconformities: Gaps in the Record..................................................................................................................27
12.6 Stratigraphic Formations and Their Correlation.................................................................................................27
12.7 The Geologic Column.........................................................................................................................................28
12.8 How Do We Determine Numerical Age? The Radiometric Clock.......................................................................28
12.9 How Do We Add Numerical Ages to the Geologic Column?...............................................................................28
Chapter 13: A Biography of Earth..................................................................................................................................29
13.1 Introduction.......................................................................................................................................................29
13.5 The Proterozoic Eon: Transition to the Modern World......................................................................................29
13.6 The Phanerozoic Eon: Life Diversifies, and Today’s Continents From................................................................29
13.8 The Mesozoic Era: When Dinosaurs Ruled.........................................................................................................30
13.9 The Cenozoic Era: The Final Stretch to the Present............................................................................................30
65 test bank questions and answers..............................................................................................................................31
Part 1: The Universe and Our Planet..........................................................................................................................31
Part 2: The Earth’s Structure......................................................................................................................................31
Part 3: Plate Tectonics...............................................................................................................................................31
Part 4: Rocks and Minerals.........................................................................................................................................32
Part 5: Sedimentary and Metamorphic Rocks............................................................................................................32
Part 6: Volcanoes and Earthquakes............................................................................................................................32
Part 7: Mountain Building and Crustal Deformation..................................................................................................32
50 core concepts explained alphabetically....................................................................................................................35
25 most important learning objectives..........................................................................................................................36
, Summary earth portrait of a planet 7th edition 2022 stephen marshak chapters 1 - 13
SUMMARY: EARTH, PORTRAIT OF A PLANET
Galaxy: An immense system of hundreds of billions of stars.
Chapter 1: An Evolving Image of the Earth’s Position and Shape
A geocentric model of the Universe placed the Earth at the center of the Universe, with
the planets and Sun orbiting around the Earth within a celestial sphere speckled with
stars. The heliocentric model placed the Sun at the center.
The heliocentric model did not gain wide popularity until the Renaissance.
Geocentric Universe concept: An ancient Greek idea suggesting that the Earth sat motionless in the
center of the Universe while stars and other planets and the Sun orbited around it.
Heliocentric Universe concept: An idea proposed by Greek philosophers around 250 B.C.E. suggesting
that all heavenly objects including the Earth orbited the Sun.
1.2 A Sense of Scale
Eratosthenes was able to measure the size of the Earth in ancient times, but it was not until
fairly recently that astronomers accurately determined the distances to the Sun, planets,
and stars, Distances in the Universe are so large that they must be measured in light years.
Light year: The distance that light travels in one Earth year (about 6 trillion miles or 9.5 trillion km).
1.3 The Modern Image of the Universe
The Earth is one of eight planets orbiting the Sun, and this Solar System lies on the outer
edge of a slowly revolving galaxy, the Milky Way, which is composed of about 300 billion
stars. The Universe contains at least hundreds of billions of galaxies.
1.4 How Did the Universe Form?
The red shift of light from distant galaxies, a manifestation of the Doppler effect, indicates
that all distant galaxies are moving away from the Earth. This observation leads to the
expanding Universe theory. Most astronomers agree that this expansion began after the
Big Bang, a cataclysmic explosion about 13.7 billion years ago.
Doppler effect: The phenomenon in which the frequency of wave energy appears to change when a
moving source of wave energy passes an observer.
Expanding Universe theory: The theory that the whole Universe must be expanding because
galaxies in every direction seem to be moving away from us.
1.5 Making Order from Chaos
The first atoms (hydrogen and helium) of the Universe developed soon after the Big
Bang. These atoms formed vast gas clouds, called nebulae.
According to the nebular theory of planet formation, gravity caused clumps of gas in the
nebulae to coalesce into revolving balls. As these balls of gas collapsed inward, the
evolved into flattened disks with bulbous centers. The protostars at the center of these
disks eventually became dense and hot enough that fusion reaction began in them. When
this happened, they became true stars, emitting heat and light.
Heavier element form during fusion reactions in stars; the heaviest are mostly made
during supernova explosions. The Earth and the lige forms on it contain elements that
could only have been produced during the life cycle of stars. Thus, we are all made of
stardust.
, Summary earth portrait of a planet 7th edition 2022 stephen marshak chapters 1 - 13
Nebula: A cloud of gas or dust in space.
Protostar: A dense body of gas that is collapsing inward because of gravitational forces and that
may eventually become a star.
Supernova: A short-lived, very bright object in space that results from the cataclysmic explosion
marking the death of a very large star; the explosion ejects large quantities of matter into space to
form new nebulae.
1.6 We Are All Made of Stardust
Planets developed from the rings of gas and dust, the planetary nebulae, that
surrounded protostars. The gas condensed into planetesimals that then clumped
together to form protoplanets, and finaly true planets. The rocky and metallic balls in the
inner part of the Solar System did not acquire huge gas coatings; they became the
terrestrial planets. Outer rings grew into gas-giant planets.
The Moon formed from debris ejected when a Mars-sized planet collided with the Earth
early during the history of the Solar System.
A planet assumes a near-spherical shape when it becomes so soft that gravity can smooth
out irregularities.
Comet: A ball of ice and dust, probably remaining from the formation of the solar system, that orbits
the Sun.
Differentiation: The splitting of light into many tiny beams that interfere with one another.
Meteorites: A piece of rock or metal alloy that fell from space and landed on Earth.
Nebular theory of planet formation: The concept that planets grow out of rings of gas, dust, and ice
surrounding a new-born star.
Planetesimals: Tiny, solid pieces of rock and metal that collect in a planetary nebula and eventually
accumulate to form a planet.
Protoplanetary disk: A ring of gas and dust that surrounded the newborn Sun, from which the
planets were formed.
Protoplanet: A body that grows by the accumulation of planetesimals but has not yet become big
enough to be called a planet.
Terrestrial: A term used to describe the inner, Earth-like planets.
Chapter 2: Journey to the Center of the Earth
2.1 Introduction
2.2 Welcome to the Neighborhood
The Earth has a magnetic field that shields it from solar wind. Closer to Earth, the
field creates the Van Allen belts, which trap cosmic rays.
Dipole: A magnetic field with a north and south pole, like that of a bar magnet.
Magnetic field: The region affected by the force emanating from a magnet.
2.3 The Atmosphere
A layer of gas surrounds the Earth. This atmosphere consists of 78% nitrogen (N), 21%
oxygen(O), and 1% other gases. Air pressure decreases with elevation, so 50% of the gas
in the atmosphere resides below 5,5 km.
Atmosphere: A layer of gases that surrounds a planet.
, Summary earth portrait of a planet 7th edition 2022 stephen marshak chapters 1 - 13
Contents
Chapter 1: An Evolving Image of the Earth’s Position and Shape....................................................................................5
1.2 A Sense of Scale.....................................................................................................................................................5
1.3 The Modern Image of the Universe.......................................................................................................................5
1.4 How Did the Universe Form?.................................................................................................................................5
1.5 Making Order from Chaos......................................................................................................................................5
1.6 We Are All Made of Stardust..................................................................................................................................6
Chapter 2: Journey to the Center of the Earth.................................................................................................................6
2.1 Introduction...........................................................................................................................................................6
2.3 The Atmosphere....................................................................................................................................................6
2.4 Land and Oceans....................................................................................................................................................7
2.5 What is the Earth made of?...................................................................................................................................7
2.6 How do we know that the Earth had layers?.........................................................................................................7
2.7 What are the layers made of?................................................................................................................................7
2.8 The Lithosphere and Asthenosphere.....................................................................................................................8
Chapter 3: Drifting Continents and Spreading Seas.........................................................................................................8
3.1 Introduction...........................................................................................................................................................8
3.2 What was Wegener’s evidence for continental drift?............................................................................................8
3.3 Setting the stage for the discovery of sea-floor spreading.....................................................................................8
3.4 Harry Hess and his “Essay in Geopoetry”...............................................................................................................9
3.5 Marine magnetic anomalies: Evidence for sea-floor spreading.............................................................................9
3.6 Deep-sea drilling: Further evidence.......................................................................................................................9
Chapter 4: The Way the Earth Works: Plate Tectonics...................................................................................................10
4.1 Introduction.........................................................................................................................................................10
4.3 Divergent plate boundaries and sea-floor spreading...........................................................................................10
4.4 Convergent plate boundaries and subduction.....................................................................................................10
4.5 Transform plate boundaries.................................................................................................................................10
4.6 Special locations in the plate mosaic...................................................................................................................11
4.7 How do plate boundaries form and die?..............................................................................................................11
4.8 What drives plate motion?...................................................................................................................................11
Chapter 5: Patterns in Nature: Minerals........................................................................................................................11
5.1 Introduction.........................................................................................................................................................11
5.3 Beauty in Patterns: Chemicals and Their Structure..............................................................................................12
5.4 How Can You Tell One Mineral from Another......................................................................................................12
5.5 Organize Our Knowledge: Mineral Classification.................................................................................................12
5.6 Something Precious: Gems!.................................................................................................................................13
Chapter 6: Up From the Inferno: Magma and Igneous Rocks........................................................................................13
6.1 Introduction.........................................................................................................................................................13
6.2 Why does magma form?......................................................................................................................................13
6.3 What is magma made of?....................................................................................................................................13
, Summary earth portrait of a planet 7th edition 2022 stephen marshak chapters 1 - 13
6.4 Moving magma and lava......................................................................................................................................13
6.5 How do extrusive and intrusive environments differ...........................................................................................14
6.6 Transforming magma into rock............................................................................................................................14
6.7 Igneous rock textures: what do they tell us?.......................................................................................................14
6.8 Classifying igneous rocks......................................................................................................................................14
Chapter 7: A Surface Veneer: Sediments, Soils and Sedimentary Rocks........................................................................15
7.1 Introduction.........................................................................................................................................................15
7.2 How does weathering lead to sediment formation?............................................................................................15
7.3 Soil: Sediment Interwoven with Life....................................................................................................................15
7.9 How Do We Recognize Depositional Environments?...........................................................................................17
7.10 Sedimentary Basins............................................................................................................................................17
7.11 Diagenesis..........................................................................................................................................................17
Chapter 8: Metamorphism: A Process of Change..........................................................................................................17
8.1 Introduction.........................................................................................................................................................17
8.2 What Happens During Metamorphism?..............................................................................................................17
8.3 What Causes Metamorphism?.............................................................................................................................17
8.4 How Do We Classify Metamorphic Rocks?...........................................................................................................18
8.5 Describing the Intensity of Metamorphism.........................................................................................................18
8.6 Where Does Metamorphism Occur?....................................................................................................................18
8.7 Where Do You Find Metamorphic Rocks?............................................................................................................19
Chapter 9: The Wrath of Vulcan: Volcanic Eruptions.....................................................................................................19
9.1 Introduction.........................................................................................................................................................19
9.3 The Architecture and Shape of Volcanoes...........................................................................................................20
9.4 Eruptive Styles: Will It Flow, or Will It Blow?........................................................................................................20
9.5 Hot-Spot Eruptions...............................................................................................................................................20
9.6 Eruptions along Plate Boundaries and Rifts.........................................................................................................21
9.8 Protection from Vulcan’s Wrath..........................................................................................................................21
9.9 The Effect of Volcanoes on Climate and Civilization.............................................................................................21
9.10 Volcanoes on Other Planets...............................................................................................................................21
Chapter 10: A Violent Pulse: Earthquakes......................................................................................................................21
10.1 Introduction.......................................................................................................................................................21
10.2 What Causes Earthquakes to Happen?..............................................................................................................21
10.3 How does Earthquake Energy Travel?................................................................................................................22
10.4 How Do We Measure and Locate Earthquakes?................................................................................................22
10.5 Where and Why Do Earthquakes Occur?...........................................................................................................23
10.6 How Do Earthquakes Cause Damage?...............................................................................................................23
10.7 Can We Predict the “Big One”?..........................................................................................................................23
10.8 Earthquake Engineering and Zoning..................................................................................................................24
Chapter 11: Crags, Cracks, and Crumples: Crustal Deformation and Mountain Building...............................................24
11.1 Introduction’......................................................................................................................................................24
11.3 Rock Deformation in the Earth’s Crust...............................................................................................................24
, Summary earth portrait of a planet 7th edition 2022 stephen marshak chapters 1 - 13
11.4 What Structures From During Brittle Deformation?..........................................................................................24
11.5 What Structures From Due to Ductile Deformation?.........................................................................................25
11.6 Igneous, Sedimentary and Metamorphic Processes in Orogenic Belts..............................................................25
11.8 Causes of Mountain Building.............................................................................................................................26
11.9 Cratons and the Deformation within Them.......................................................................................................26
11.10 Life Story of a Mountain Range: A Case Study.................................................................................................26
Chapter 12: Deep Time: How Old Is Old?.......................................................................................................................26
12.1 Introduction.......................................................................................................................................................26
12.2 Time: A Human Obsession.................................................................................................................................27
12.4 Principles for Defining Relative Age...................................................................................................................27
12.5 Unconformities: Gaps in the Record..................................................................................................................27
12.6 Stratigraphic Formations and Their Correlation.................................................................................................27
12.7 The Geologic Column.........................................................................................................................................28
12.8 How Do We Determine Numerical Age? The Radiometric Clock.......................................................................28
12.9 How Do We Add Numerical Ages to the Geologic Column?...............................................................................28
Chapter 13: A Biography of Earth..................................................................................................................................29
13.1 Introduction.......................................................................................................................................................29
13.5 The Proterozoic Eon: Transition to the Modern World......................................................................................29
13.6 The Phanerozoic Eon: Life Diversifies, and Today’s Continents From................................................................29
13.8 The Mesozoic Era: When Dinosaurs Ruled.........................................................................................................30
13.9 The Cenozoic Era: The Final Stretch to the Present............................................................................................30
65 test bank questions and answers..............................................................................................................................31
Part 1: The Universe and Our Planet..........................................................................................................................31
Part 2: The Earth’s Structure......................................................................................................................................31
Part 3: Plate Tectonics...............................................................................................................................................31
Part 4: Rocks and Minerals.........................................................................................................................................32
Part 5: Sedimentary and Metamorphic Rocks............................................................................................................32
Part 6: Volcanoes and Earthquakes............................................................................................................................32
Part 7: Mountain Building and Crustal Deformation..................................................................................................32
50 core concepts explained alphabetically....................................................................................................................35
25 most important learning objectives..........................................................................................................................36
, Summary earth portrait of a planet 7th edition 2022 stephen marshak chapters 1 - 13
SUMMARY: EARTH, PORTRAIT OF A PLANET
Galaxy: An immense system of hundreds of billions of stars.
Chapter 1: An Evolving Image of the Earth’s Position and Shape
A geocentric model of the Universe placed the Earth at the center of the Universe, with
the planets and Sun orbiting around the Earth within a celestial sphere speckled with
stars. The heliocentric model placed the Sun at the center.
The heliocentric model did not gain wide popularity until the Renaissance.
Geocentric Universe concept: An ancient Greek idea suggesting that the Earth sat motionless in the
center of the Universe while stars and other planets and the Sun orbited around it.
Heliocentric Universe concept: An idea proposed by Greek philosophers around 250 B.C.E. suggesting
that all heavenly objects including the Earth orbited the Sun.
1.2 A Sense of Scale
Eratosthenes was able to measure the size of the Earth in ancient times, but it was not until
fairly recently that astronomers accurately determined the distances to the Sun, planets,
and stars, Distances in the Universe are so large that they must be measured in light years.
Light year: The distance that light travels in one Earth year (about 6 trillion miles or 9.5 trillion km).
1.3 The Modern Image of the Universe
The Earth is one of eight planets orbiting the Sun, and this Solar System lies on the outer
edge of a slowly revolving galaxy, the Milky Way, which is composed of about 300 billion
stars. The Universe contains at least hundreds of billions of galaxies.
1.4 How Did the Universe Form?
The red shift of light from distant galaxies, a manifestation of the Doppler effect, indicates
that all distant galaxies are moving away from the Earth. This observation leads to the
expanding Universe theory. Most astronomers agree that this expansion began after the
Big Bang, a cataclysmic explosion about 13.7 billion years ago.
Doppler effect: The phenomenon in which the frequency of wave energy appears to change when a
moving source of wave energy passes an observer.
Expanding Universe theory: The theory that the whole Universe must be expanding because
galaxies in every direction seem to be moving away from us.
1.5 Making Order from Chaos
The first atoms (hydrogen and helium) of the Universe developed soon after the Big
Bang. These atoms formed vast gas clouds, called nebulae.
According to the nebular theory of planet formation, gravity caused clumps of gas in the
nebulae to coalesce into revolving balls. As these balls of gas collapsed inward, the
evolved into flattened disks with bulbous centers. The protostars at the center of these
disks eventually became dense and hot enough that fusion reaction began in them. When
this happened, they became true stars, emitting heat and light.
Heavier element form during fusion reactions in stars; the heaviest are mostly made
during supernova explosions. The Earth and the lige forms on it contain elements that
could only have been produced during the life cycle of stars. Thus, we are all made of
stardust.
, Summary earth portrait of a planet 7th edition 2022 stephen marshak chapters 1 - 13
Nebula: A cloud of gas or dust in space.
Protostar: A dense body of gas that is collapsing inward because of gravitational forces and that
may eventually become a star.
Supernova: A short-lived, very bright object in space that results from the cataclysmic explosion
marking the death of a very large star; the explosion ejects large quantities of matter into space to
form new nebulae.
1.6 We Are All Made of Stardust
Planets developed from the rings of gas and dust, the planetary nebulae, that
surrounded protostars. The gas condensed into planetesimals that then clumped
together to form protoplanets, and finaly true planets. The rocky and metallic balls in the
inner part of the Solar System did not acquire huge gas coatings; they became the
terrestrial planets. Outer rings grew into gas-giant planets.
The Moon formed from debris ejected when a Mars-sized planet collided with the Earth
early during the history of the Solar System.
A planet assumes a near-spherical shape when it becomes so soft that gravity can smooth
out irregularities.
Comet: A ball of ice and dust, probably remaining from the formation of the solar system, that orbits
the Sun.
Differentiation: The splitting of light into many tiny beams that interfere with one another.
Meteorites: A piece of rock or metal alloy that fell from space and landed on Earth.
Nebular theory of planet formation: The concept that planets grow out of rings of gas, dust, and ice
surrounding a new-born star.
Planetesimals: Tiny, solid pieces of rock and metal that collect in a planetary nebula and eventually
accumulate to form a planet.
Protoplanetary disk: A ring of gas and dust that surrounded the newborn Sun, from which the
planets were formed.
Protoplanet: A body that grows by the accumulation of planetesimals but has not yet become big
enough to be called a planet.
Terrestrial: A term used to describe the inner, Earth-like planets.
Chapter 2: Journey to the Center of the Earth
2.1 Introduction
2.2 Welcome to the Neighborhood
The Earth has a magnetic field that shields it from solar wind. Closer to Earth, the
field creates the Van Allen belts, which trap cosmic rays.
Dipole: A magnetic field with a north and south pole, like that of a bar magnet.
Magnetic field: The region affected by the force emanating from a magnet.
2.3 The Atmosphere
A layer of gas surrounds the Earth. This atmosphere consists of 78% nitrogen (N), 21%
oxygen(O), and 1% other gases. Air pressure decreases with elevation, so 50% of the gas
in the atmosphere resides below 5,5 km.
Atmosphere: A layer of gases that surrounds a planet.
