CH. 1: Introduction to Geology

Question 1

How old is Earth?

Answer 1

4. 6 billion years old
   - Geologists are able to assign fairly accurate dates to events in Earth’s history using radioactivity to determine numerical dates.

Question 2

Which of the following is the thickest sphere on Earth?

Answer 2

geosphere

Question 3

Wet mud and earthworm found on the edge of a lake would be considered to be part of which sphere?

Answer 3

geosphere + hydrosphere + biosphere

Question 4

On Earth, chemical differentiation leads to the formation of layers in Earth based on the ____ of the materials that make up those layers.

Answer 4

density

Question 5

Between continental and oceanic crust, ____ crust is denser and ____ crust is thicker/

Answer 5

oceanic; continental

Question 6

Which layers in Earth’s geosphere are liquid?

Answer 6

outer core

Question 7

What defines the boundary between the lithosphere and asthenosphere?

Answer 7

This is a temperature boundary, where peridotite mantle is hot enough to behave more like a plastic than a rigid solid

Question 8

If you have a metamorphic rock and you bury it and heat it until it melts, and then bring it closer to the surface where it cools and solidifies again, the resulting rock would be ____.

Answer 8

igneous

Question 9

Please identify the following features:

the light blue, near coast feature off the coast of TX and FL

the fractured region of the Indian Ocean in the center of this image

the central dark region of Africa at the Equator

the flat region of the Pacific Ocean basin show below

the dark blue very deep feature off the east coast of Japan

Answer 9

1. continental shelf
2. ocean ridge
3. craton
4. abyssal plain
5. trench

Question 10

The layers of Earth’s geosphere are defied based on which TWO sets of characteristics?

Answer 10

chemical composition

physical properties

Question 11

The ____ is the most widely accepted view of the origin of our solar system. This describes the beginning of the solar system asa large cloud of space gas and dust that slowly condensed and contracted, forming the current solar system.

Answer 11

The Nebular Theory

Question 12

Which of the following describe sedimentary rocks?

Answer 12

formed by lithification of pre-existing rock

Question 13

Why is data collection important to scientists?

Answer 13

data are used to support or disprove a hypothesis

Question 14

The temperature of the Earth _____ with depth.

Answer 14

increases

Question 15

Since temperatures in Earth increase with depth, why is the inner core solid?

Answer 15

the pressures in the core are immense and keep it in a solid state despite the temperature

Question 16

The Earth’s magnetic field is generated where?

Answer 16

Earth’s core

Question 17

Label each of the following as a process that occurs at Earth’s surface, in Earth’s shallow subsurface, or in Earth’s deep subsurface.

shallow subsurface sediment undergoing lithification

deep subsurface melting

surface lava crystallizing

Answer 17

1. shallow subsurface
2. deep subsurface
3. surface

Question 18

On the following map, a-e point directly to wither oceanic or continental crust. Choose the correct crust type for each.

Answer 18

A = oceanic crust

B = continental crust

C = continental crust

D = oceanic crust

E = continental crust

Question 19

The Big Bang describes ____ and is estimated to have occurred ____

Answer 19

the formation of the universe; between 10 billion and 15 billion years ago

Question 20

A very old stable region of the continent composed of igneous and metamorphic rock is a called a continental ____. The edge of the continent that is submerged below sea levels is called the continental ____.

Answer 20

craton/shield; shelf

Question 21

Which of the following correctly states the order in which major features of North America were formed?

Answer 21

Canadian Shield, Appalachians, North American Cordillera

• The Canadian Shield is the oldest part of the continent while the Cordillera is the youngest.

Question 22

Which statement accurately describes continental shields?

Answer 22

very old, stable regions composed of igneous and metamorphic rocks

Question 23

If stable platforms represent sedimentary rocks that cover continental shields, then what statement must be true?

Answer 23

the sedimentary rock atop the younger platforms must be younger than continental shields.

Question 24

The __________ is an example of an old mountain belt, while the Himalayas represent a(n) __________.

Answer 24

Appalachian Mountains; young mountain belt

Question 25

What main characteristics are used to distinguish the two types of mountain belts?

Answer 25

Age and degree of erosion

Question 26

The layers of Earth are based on what two sets of characteristics?

Answer 26

Chemical composition and physical properties

Question 27

What is the “D” layer?

Answer 27

a partially molten layer above the outer core at the base of the mantle.

Question 28

The upper mantle can be divided into the asthenosphere and lithosphere based on what physical properties?

Answer 28

the asthenosphere is solid, but mobile, while the lithosphere is solid and relatively rigid.

Question 29

What are the two types of crust?

Answer 29

oceanic and continental

Question 30

What happens to the atmosphere as you move away from Earth’s surface?

Answer 30

the atmosphere thins

Question 31

What is the category name for the largest division of time used on the geologic time scale?

Answer 31

Eon

Question 32

Why is the geologic time scale more detailed in the Phanerozoic than in previous eons?

Answer 32

The Phanerozoic Eon is more detailed because of the presence of organisms with hard parts and the rapid increase in biodiversity.

• The Phanerozoic is the eon of complex life. Previous eons were characterized by single-celled organisms, which are much more difficult to preserve.

Question 33

The Jurassic Period lies in the _____ Era, which was dominated by large terrestrial vertebrates, or _____.

Answer 33

Mesozoic; dinosaurs

• The Mesozoic Era was dominated by dinosaurs.

Question 34

Using a calendar year as an analogy to the geologic time scale, when do the oldest anatomically modern humans appear on Earth?

Answer 34

The oldest human fossils show up at about eleven minutes to midnight on December 31st.

• We represent only a very small proportion of the geologic record. If using a calendar year as an analogy, we represent the last eleven minutes of the year.

Question 35

Name the epoch, period, era and eon in which we currently live.

Answer 35

We live in the Holocene Epoch of the Quaternary Period, which is part of the Cenozoic Era and Phanerozoic Eon.

• We represent only a very small and recent proportion of the vast geologic record.

Question 36

The three main rock types can include layers. But the layers are formed for different reasons. For instance, layers in sedimentary rocks occur when there is a change in sediment deposition conditions, such as an environmental change that causes an area that was a beach to become a lagoon. The size of sediment is smaller than the sand previously accumulated. Layers in metamorphic rocks, called foliation, form when the orientation of elongated flat platy minerals changes align themselves in response to increasing pressure. Distinct layers in igneous rocks may form when magma moves into fissures within another rock.

Determine the Rock Types

1. Layers are the result of alignment of minerals under directional pressure.
2. Layers are the result of deposition of different types and sizes of particles in a water body
3. Layers are the result of magma flowing into a crack in other rock.

Answer 36

1. metamorphic layers
2. sedimentary layers
3. igneous layers

Question 37

ROCK CYCLE

Answer 37

The rock cycle is a concept that explains the cycling of rocks and their basic constituents in nature.The majority of rocks in Earth’s crust are composed of silicate minerals, which melt at high temperatures. This molten material is called magma. Since it is less dense than the surrounding rock, it will ascend toward the surface. As magma slowly cools, silicate minerals crystallize to form intrusive igneous rocks. If the magma reaches the surface, it is called lava. Lava cools much more quickly than magma, forming extrusive igneous rocks.At Earth’s surface, rocks will be subjected to weathering agents such as ice, wind, and flowing water, and will break down to small fragments called sediments. Sediments undergo erosion, transport, and deposition before being compacted and cemented into sedimentary rocks—a process called lithification. For example, in ocean basins, sediments that settle to the bottom are continuously buried under overlying material and are cemented together.Sedimentary rocks that are deeply buried and under high pressure, especially during mountain building, will change into metamorphic rocks. Metamorphism is achieved without any melting occurring in the rock. As pressure rises, temperature also rises, and metamorphic rocks may turn into magma if temperatures rise above the melting point of the minerals that make up these rocks.
Likewise, igneous rocks can change into magma if temperatures rise above the melting point of its minerals.

Question 38

In the list shown below, label each item for the location where it primarily occurs: 1) on Earth’s surface, 2) Earth’s shallow subsurface, or 3) Earth’s deep subsurface (many miles/km below the surface).

1. Lava cooling and undergoing crystallization to form extrusive igneous rocks
2. weathering, transport, deposition
3. sediment undergoing lithification
4. rock melting
5. high temperature, high pressure high grade metamorphism

Answer 38

1. Earth’s surface
2. Earth’s surface
3. Earth’s shallow subsurface
4. Earth’s deep subsurface
5. Earth’s deep subsurface

Question 39

Which of the following rock types is most abundant on Earth’s land surface?

Answer 39

sedimentary rocks

Question 40

The nebular theory is the most widely accepted view of the origin of our solar system. Which of the following is a short description of the nebular theory?

Answer 40

A large cloud of space gas and dust condensed and contracted to form a rotating disk with a star formed at the center. Repeated collisions caused bodies to coalesce, leading to the current configuration of our solar system.

Question 41

The enormous cloud of gas and dust initially condensed due to particle attraction. What force then pulled the cloud into a flat disk shape?

Answer 41

the inward pull of gravity

Question 42

What object or class of objects makes up most of the solar system’s mass?

Answer 42

The Sun

Question 43

Through the course of time, bodies in our solar system have become __________ and __________ due to collisions.

Answer 43

fewer in number; larger in size

Question 44

Which word describes a system in which energy moves freely in and out, but no matter enters or leaves?

Answer 44

closed

• A closed system describes a system in which energy moves freely in and out, but no matter enters or leaves.

A closed system is self-contained with regard to matter. Energy moves freely in and out of a closed system but no matter enters or leaves the system. In an open system, both energy and matter flow into and out of the system. Feedback is the system of mechanisms that cause change or resist change and stabilize the system. When systems are in balance, they are described as being in equilibrium.

Question 45

Which of the following best describes the fundamental concept of superposition?

Answer 45

Any sedimentary deposit accumulates on top of older rock or sediment layers.

• The following best describes the fundamental concept of superposition: Any sedimentary deposit accumulates on top of older rock or sediment layers.

The basic rule applies to materials that were originally deposited at Earth’s surface such as layers of sedimentary rock and volcanic lava flows. Stated another way, a layer is older than the ones above it and younger than the ones below.

Question 46

Which layer forms the relatively cool, brittle plates of Earth’s crust?

Answer 46

the top of the lithosphere

• The top of the lithosphere forms the relatively cool, brittle plates of Earth’s crust.

Beneath the lithosphere lies a comparatively weak layer known as the asthenosphere (“weak”-“sphere”). The top portion of the asthenosphere has a temperature/pressure regime that results in a small amount of melting. Within this very weak zone the lithosphere is detached from the layer below. Thus, the lithosphere is able to move independently of the asthenosphere.

Question 47

What type of rocks form by crystallization and consolidation of molten magma?

Answer 47

igneous

• Igneous rocks (ignis = fire) form by crystallization and consolidation of molten magma.

Magma is melted rock that can form at various levels deep within Earth’s crust and upper mantle. As magma cools, crystals of various minerals form and grow.

Sedimentary rocks are composed of sediments that are derived from particles of preexisting rocks by the processes of weathering, erosion, and transportation or by deposition by organisms. Metamorphic rocks are rocks that have been changed by heat and pressure.

Question 48

What are the most prominent features on the ocean floor?

Answer 48

mid-oceanic ridges

• The most prominent feature on the ocean floor is mid-oceanic ridges.

The mid-oceanic ridges form a continuous belt that winds for more than 70,000 kilometers (43,000 miles) around the globe in a manner similar to the seams of a baseball.

Deep ocean trenches are deep depressions that are occasionally more than 11,000 meters (35,000 feet) deep. The deep ocean trenches are relatively narrow and represent only a small fraction of the ocean floor. Seamounts are submerged volcanic structures dotting the ocean floor that sometimes form long narrow chains. Volcanic activity has also produced several large lava plateaus on the ocean floor.

Question 49

Where are active mountain belts most likely to be found?

Answer 49

along the margins of continents

• Active mountain belts are most likely to be found along the margins of continents.

Young mountain belts tend to be long, narrow topographic features at the margins of continents. Flat stable areas, cratons, are typically located in the interior of the continents.

Question 50

Where in Earth is the asthenosphere?

Answer 50

in the mantle under the lithosphere

• The asthenosphere is in the mantle under the lithosphere.

Beneath the crustal lithosphere (“rock”; “sphere”) lies a soft, comparably weak layer known as the asthenosphere (“weak”; “sphere”). The asthenosphere is part of the upper mantle. Earth’s crust (lithosphere) is a relatively thin, rocky outer layer. The crust is divided into two different types—continental crust and oceanic crust. The inner core is thought to be an iron-rich alloy. The core is divided into two regions—the liquid outer core and the solid inner core.

Question 51

What are the basic differences between the disciplines of physical and historical geology?

Answer 51

Physical geology includes the study of how rocks form and of how erosion shapes the land surface; historical geology involves the study of rock strata, fossils, and geologic events, utilizing the geologic time scale as a reference.

• Historical geology strives to establish an orderly chronological arrangement of the multitude of physical and biological changes that have occurred in the geologic past.

Question 52

The __________ refers to the sum total of all life on Earth.

Answer 52

biosphere

• The biosphere refers to the sum total of all life on Earth.

Earth can be thought of as consisting of four major spheres: the hydrosphere, atmosphere, geosphere, and biosphere. The biosphere is the totality of all plant and animal life on our planet and it interacts with each of the three physical spheres (hydrosphere, atmosphere, and geosphere).

The hydrosphere is a dynamic mass of water that is continually on the move, evaporating from the oceans to the atmosphere, precipitating to the land, and running back to the ocean again. The geosphere is the solid Earth, and the atmosphere is the life-giving gaseous envelope surrounding Earth.

Question 53

What two processes occur during lithification of sedimentary rocks?

Answer 53

compaction and cementation

• Compaction and cementation occur during lithification of sedimentary rocks.

Cementation is the hardening and welding of sediments that formed from preexisting rock fragments. Compaction is the consolidation of sediments resulting from the weight of overlying deposits. The weight of the overlying deposits pushes the sediment grains together and reduces the amount of the pore space between the grains.

Weathering processes physically break rock into smaller pieces. Transportation is the movement of grains along Earth’s surface by wind, water, and ice. Igneous rocks form when molten rock, called magma, cools and solidifies. As magma cools, crystals of various minerals form and grow.

Question 54

What theory proposes that the bodies of the solar system formed at essentially the same time from a rotating cloud of gases and dust?

Answer 54

Nebular theory

• The Nebular theory proposes that the bodies of the solar system formed at essentially the same time from a rotating cloud of gases and dust. The orderly nature of our solar system leads most researchers to conclude that Earth and the other planets formed at essentially the same time and from the primordial material of the Sun.

The Big Bang theory proposes that there was an incomprehensibly large explosion that sent all matter of the universe flying outwards at incredible speeds. In time, the debris from this explosion, which was almost entirely hydrogen and helium, began to cool and condense into the first stars and galaxies. The Plate Tectonics theory proposes that Earth’s outer shell consists of individual plates that interact in various ways and thereby produce earthquakes, volcanoes, mountains, and the crust itself. The Heliocentric theory is the astronomical model in which Earth and the other planets revolve around a relatively stationary Sun at the center of the Solar System.

Question 55

__________ is the process by which rocks breakdown in place to produce soils.

Answer 55

weathering

• Weathering is the process by which rocks breakdown in place to produce soils.

During weathering, rocks are broken down into smaller pieces by physical, chemical, and biological processes.

Lithification is the process of converting sediments into solid rock. Subduction is the process by which oceanic lithosphere plunges (sinks) into the mantle along a convergent zone. Metamorphism refers to the process of changes in the mineral composition and texture of a rock.

Question 56

Which list below identifies the layers of the Earth in the correct order from the center outward?

Answer 56

Inner core, outer core, mantle, crust

• The following list identifies the layers of the Earth in the correct order from the center outward: Inner core, outer core, mantle, crust.

Earth’s crust is its relatively thin, rocky outer layer. The crust is divided into two different types—continental crust and oceanic crust. More than 82% of Earth’s volume is contained in the mantle, which is divided into the upper mantle and the lower mantle. The core is thought to be an iron-rich alloy. The core is divided into two zones—the liquid outer core and the solid inner core. The segregation of the material that began early in Earth’s history resulted in the formation of layers defined by their chemical composition. As material accumulated to form Earth, the temperature of our planet was steadily increasing. During this time, Earth became hot enough that iron and nickel began to melt and these heavy metals sank toward the center of our planet producing its dense iron-rich core, and the remaining material formed the crust and the mantle.

Question 57

The __________ is thought to be a liquid, metallic region in Earth’s interior.

Answer 57

outer core

• The outer core is thought to be a liquid, metallic region in Earth’s interior.

The core is thought to be an iron-rich alloy. The core is divided into two regions—the liquid outer core and the solid inner core.

More than 82% of Earth’s volume is contained in the mantle, which is divided into the upper mantle and the lower mantle. Part of the lithosphere (“rock” - “sphere”) and asthenosphere (“weak” - “sphere”) lie in the upper mantle and crust.

Question 58

Which of the following is not one of the possible steps of a scientific investigation?

Answer 58

The publication of conclusions without prior experimentation or observation

• The development of new scientific knowledge involves processes that are universally accepted. Scientists collect facts through observation and measurement. Once facts have been gathered and principles have been formulated to describe natural phenomena, investigators try to explain how or why things happen in the manner observed. They do this by constructing scientific hypotheses. A hypothesis must pass years of repeated objective testing and analysis before it becomes an accepted part of scientific knowledge. An untestable hypothesis is not scientifically useful, no matter how interesting it might seem.

Question 59

Which term describes a relatively stable interior portion of a continent?

Answer 59

craton

• Craton describes a relatively stable interior portion of a continent.

The interiors of the continents, cores called cratons, have been relatively stable (undisturbed) for the last 600 million years or even longer. Typically these regions were involved in mountain-building episodes very early in Earth’s history.

Within the stable cratons, expansive, flat regions called shields are composed of deformed crystalline rock. Other flat areas of cratons exist in which highly deformed rocks, like those in the shields, are covered by a relatively thin veneer of sedimentary rocks. These areas are called stable platforms. The most prominent topographic features of the continents are linear mountain belts, which have been tectonically active within the past 100 million years.

Question 60

What geological theory is often paraphrased as “the present is the key to the past”?

Answer 60

Uniformitarianism

• Uniformitarianism is the geological theory that is often paraphrased as “the present is the key to the past.”

It states that the physical, chemical, and biological laws that operate today have also operated in the past. James Hutton published Theory of the Earth in 1795. In his work, Hutton put forth the fundamental principle of uniformitarianism, which is the pillar of geology today. Uniformitarianism can be simply stated as “the present is the key to the past.”

Superposition tells geologists that the oldest rocks are usually on the bottom of a sedimentary sequence. Catastrophism states that Earth’s landscapes had been shaped primarily by great catastrophes. Fossil succession states that fossil organisms succeed one another in a definite and determinable order.

Question 61

What material is thought to form the core of Earth?

Answer 61

Solid iron-nickel alloy

• The composition of the inner core is thought to be solid iron-nickel alloy.

The core is divided into two regions—the liquid outer core and the solid inner core. The segregation of the material that began early in Earth’s history resulted in the formation of layers defined by their chemical composition. As material accumulated to form Earth, the temperature of our planet was steadily increasing. During this time, Earth became hot enough that iron and nickel began to melt. These heavy metals sank toward the center of our planet producing its dense iron rich core, and the remaining material formed the crust and the mantle.

Igneous rocks that form at the surface are described as extrusive and are usually fine grained. An abundant and important example is basalt. Coarse-grained igneous rocks that form far below the surface are called intrusive. A common and important example is granite. Peridotite is an igneous rock thought to be abundant in the upper mantle.

Question 62

The __________ is the thinnest layer of Earth.

Answer 62

crust

• The crust is the thinnest layer of Earth.

Earth’s crust is the relatively thin rocky outer layer. The crust is divided into two different types—continental crust and oceanic crust. The crust is approximately 7-70 km thick.

The mantle, 2,830 km thick, is divided into the upper mantle and the lower mantle.

The core, 3,486 km thick, is thought to be an iron-rich alloy. The core is divided into two regions—the liquid outer core and the solid inner core.

Question 63

A __________ is a well-tested and widely accepted view that best explains certain scientific observations.

Answer 63

theory

• A theory is a well-tested and widely accepted view that best explains certain scientific observations.

The development of new scientific knowledge involves processes that are universally accepted. To determine what is happening in the natural world, scientists collect scientific facts through observation and measurement. Once facts have been gathered, investigators construct scientific hypotheses. A hypothesis is an untested explanation that tries to explain how or why things happen in the manner observed. A hypothesis may be elevated to the status of scientific theory when it has survived extensive scrutiny and when competing hypotheses have been eliminated.

Question 64

Where in the ocean basin would we find the continental shelf?

Answer 64

Between the continent and the continental slope

• The continental shelf is located between the continent and the continental slope.

Although land and sea meet at the shoreline, this is not the boundary between the continents and the ocean basins. Rather, along most coasts a gently sloping platform of material, the continental shelf, extends seaward from the shore. The continental slope marks the boundary between the continent and the deep-ocean basin. The slope is a relatively steep drop off that extends from the outer edge of the continental shelf to the floor of the deep ocean.

Question 65

Which ancient, highly influential Greek philosopher wrote about nature and the workings of Earth?

Answer 65

Aristotle

• Aristotle was the most influential Greek philosopher who wrote about nature and the workings of Earth.

Writings about such topics as fossils, gems, earthquakes, and volcanoes date back to the early Greeks, more than 2,300 years ago. Aristotle’s explanations about the natural world were not based on keen observations and experiments. Instead, they were arbitrary pronouncements. Although Aristotle’s explanations were suitable for his day, his ideas continued to be used to explain geologic processes for many centuries, which slowed the acceptance of more modern ideas.

Question 66

Which 18th-century English geologist proposed uniformitarianism?

Answer 66

James Hutton

• James Hutton proposed uniformitarianism.

He published the Theory of the Earth in 1795. In his work, Hutton put forth the fundamental principle of uniformitarianism, which is the pillar of geology today. Uniformitarianism states that “the physical, chemical, and biological laws that operate today have also operated in the past” and can be simply stated as ”the present is the key to the past.”

Charles Lyell effectively demonstrated that Earth had experienced many episodes of mountain building and erosion, which must have required great spans of geologic time. Isaac Newton is credited with the development of calculus. Isaac Newton’s and Gottfried W. Leibniz’s work in calculus is an example of two different researchers coming to similar conclusions almost simultaneously. In scientific research, the first researcher to publish his or her work in a scientific journal is given credit. In the case of Newton and Leibniz, Newton’s work was published first and he is therefore credited with the development of calculus.

In the mid-1600s, James Ussher published a chronology of human and Earth history in which he determined that Earth was only a few thousand years old, having been created in 4004 B.C. Ussher’s work gained widespread acceptance among Europe’s scientific and religious leaders, and his chronology was soon printed in the margins of the Bible.