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GEOS Midterm Exam with complete
solutions latest version
The five mass extinctions in Earth's history were caused by many factors - CORRECT
ANSWER-including periods of intense volcanic activity, global climate change, and
asteroid impacts.
Geological Time Chart - CORRECT ANSWER-Collectively Earth's first three eons, the
Hadean Eon, Archaean Eon, and the Proterozoic Eon, constitute 88% of Earth's history.
The top of the diagram shows the present day, and the lower parts of the diagram show
increasingly older times. Our current eon, the Phanerozoic Eon, comprises 12% of
Earth's history. Nearly all major evolutionary events of Earth history have happened in
the Phanerozoic. (B) The Phanerozoic Eon, shown in detail here, is subdivided into
numerous eras, periods, and epochs. We live in the Holocene Epoch, which is nested in
the Quaternary Period, which in turn is nested the Cenozoic Era of the Phanerozoic
Eon. Note that the Anthropocene Epoch is not included above the Holocene epoch
because scientists have not yet formally recognized it as a new epoch. (C) In this
graphic, Earth's entire history is compressed into a single year of time, with Earth and
the solar system forming on January 1 (at the bottom of the graphic) and the present
day being midnight on December 31. Each month on the calendar represents about 383
million years, and each second is about 145 years. Using this perspective, we can see
that most life-forms we are familiar with arose only recently, no earlier than mid-
"November" (kya = thousand years ago; mya = million years ago; bya = billion years
ago).
Uniformitarianism - CORRECT ANSWER-is the principle that the same gradual and
nearly imperceptible processes operating now have operated in the past.
Relative age - CORRECT ANSWER-compares the age of one object or event with the
age of another, without specifying how old either object is.
Relative age accounts for - CORRECT ANSWER-the order of events. For example, if
two trees are growing side by side and one is smaller, we might reasonably conclude
that the smaller tree is younger. We may not know how old it is in absolute terms but
only that it is younger relative to the larger tree.
BRAINSCAPE1
, BRAINSCAPE1
Apply Relative Age to Earth - CORRECT ANSWER-This concept can be applied to rock
layers in Earth's crust. A sequence of rock layers forms as layers of sediments are
deposited, one after another, and eventually harden into sedimentary rock
Absolute age - CORRECT ANSWER-is specified in years before the present
Absolute age Techniques - CORRECT ANSWER-which is given in actual numbers of
years, is determined using various dating techniques. For example, tree-ring analysis
(called dendrochronology) provides absolute ages of trees. Most trees create one new
growth ring each year. Counting the growth rings in a cut tree allows an investigator to
determine the absolute age of a tree.
radiometric dating or half-lives - CORRECT ANSWER-which involves using unstable
atoms in materials to assign ages to those materials. Radiometric dating methods,
which have been in wide use since the 1950s, provide a means by which we can
determine the absolute ages of ancient materials such as rocks, wood, and bones.
These methods are based on the premise of radioactive decay: Unstable atoms (called
parent atoms) found in some elements decay (convert) to a stable element (called
daughter atoms) at a constant rate through time. For example, the parent atom carbon-
14 decays into the stable daughter atom nitrogen-14. Young objects that contain an
unstable atom have high proportions of that parent atom because there has not been
enough time for the parent form to decay to the stable, daughter form. In very old
objects, the unstable parent atom is largely gone, having decayed to its stable form. The
time it takes for half of the parent atoms to decay to the daughter atoms is called a half-
life.
As depth increases, so does temperature; this pattern is called the geothermal gradient.
- CORRECT ANSWER-Geothermal Gradient
Factors that have created and continue to create hot earth interior - CORRECT
ANSWER-Two factors have created and continue to create a hot Earth interior:
radioactivity and friction. The most important source of Earth's internal heat is
radioactive decay of unstable elements, mainly potassium, uranium, and thorium. These
elements give off heat during the decay process.
In addition to radioactivity, friction has played and continues to play a role in heating
Earth's interior. When the Moon first formed, it was only about 24,300 km (15,000 mi)
away from Earth (compared with today's average distance of 384,399 km [238,854 mi]).
Because it was so close, the Moon's gravitational pull exerted enormous lunar tidal
forces, which distorted Earth's shape and created heat from the friction of the movement
of Earth's interior. Although it is farther away today, the Moon still exerts tidal forces on
Earth, distorting its shape, and creating a small amount of heating through friction. -
CORRECT ANSWER-
seismic waves - CORRECT ANSWER-energy released by earthquakes that travels
through Earth's interior. One way we know earth's behaviours.
BRAINSCAPE1
, BRAINSCAPE1
An earthquake - CORRECT ANSWER-is a sudden shaking of the ground caused by
movements of Earth's crust. We also have other direct and indirect evidence related to
Earth's internal structure
Earth's Layers - CORRECT ANSWER-The heaviest and most dense layers and the
greatest pressures are found at Earth's center. Outward from the center, the density of
rocks and the pressure decrease. The atmosphere and oceans are a continuum with
the solid Earth. Each layer is made of matter in solid, liquid, or gaseous states. It is no
accident that the layers are arranged this way—from most dense to least dense. As
Earth accreted from dust and gas during the formation of the solar system, the densest
materials settled deepest, and the least dense materials, like gases and water, rose to
the surface.
superposition principle - CORRECT ANSWER-states that in such a sequence of rock
layers, the oldest rocks are at the bottom, and the youngest rocks are at the top
The inner Core - CORRECT ANSWER-which extends from Earth's center to about
5,150 km (3,200 mi) below Earth's surface, is a mixture of dense elements, mostly iron
and nickel. Inner core temperatures approach 6,000°C (10,800°F). These temperatures
would melt the inner core if not for the extremely high pressure found there. The
extreme pressure in the inner core keeps the inner core solid. Atoms in molecules are
forced closer together under great pressure. As a result, to break molecular bonds and
melt rocks in the inner core, temperatures must be very high; temperatures need not be
as high to melt rocks at or near Earth's surface, where there is much less pressure.
The Outer Core - CORRECT ANSWER-surrounds the inner core, is composed of a
liquid alloy of iron and nickel. Temperatures in the outer core begin around 4,000°C
(7,232°F) and increase toward the inner core. The outer core extends to about 2,900 km
(1,800 mi) below Earth's surface. The outer core is liquid because pressures within it
are less than the pressure in the inner core; lower pressure allows the outer core to melt
and flow. This circulating liquid metal generates electrical currents and creates Earth's
magnetic field. Together, the inner and outer core make up about 15% of Earth's
volume.
Magnetosphere - CORRECT ANSWER-Earth's magnetic field forms the
magnetosphere, which surrounds the planet and shields it from the solar wind, a stream
of electrically charged particles emitted by the Sun
Lower Mantle - CORRECT ANSWER-the layer of heated and slowly deforming solid
rock that lies between the base of the crust and the outer core. The lower limit of the
lower mantle lies 2,900 km (1,800 mi) below the surface; it extends upward to
approximately 200 km (125 mi) below the surface. Temperatures in the lower mantle
range from about 4,000°C (7,232°F) near the outer core to about 1,000°C (1,832°F)
toward the crust.
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, BRAINSCAPE1
Even though the lower mantle is solid rock, it is not rigid and unmovable. Instead, it
slowly deforms and flows at a rate of about 15 cm (6 in) per year. When a solid is able
to deform and flow, its behavior is described as plastic (or ductile). Warm (but unmelted)
candle wax or beeswax is plastic in that it can be squeezed and shaped with your
fingers once it is warmed. - CORRECT ANSWER-Movement of lower mantle
The asthenosphere - CORRECT ANSWER-(from the Greek for "weak") is the layer of
the mantle found between depths of about 100 and 200 km (62 and 124 mi). It gets its
name from the fact that it is softer and weaker than the lower mantle beneath it. Like the
lower mantle, this layer of rock is solid but can flow under pressure. There is
considerably less pressure in the asthenosphere than in the lower mantle below it. As a
result, although the rocks here are still in a solid state, they are nearer to melting and
are consequently weak and easily deformed.
Upper Mantle Makeup - CORRECT ANSWER-The asthenosphere and the lithospheric
mantle (discussed next) together make up the upper mantle. The lower mantle and
upper mantle together make up the mantle, which accounts for about 84% of Earth's
volume. The mantle is composed of silicate rocks (made mostly of minerals that contain
silica) that are rich in iron and magnesium.
The Lithosphere - CORRECT ANSWER-relatively strong and consists of Earth's rigid
crust and the rigid lithospheric mantle beneath it, extending to a depth of about 100 km
(62 mi) on average (see Figure 12.11). Unlike the asthenosphere and lower mantle, the
lithosphere is not plastic and does not deform and flow. Instead, when subjected to
stresses from the moving asthenosphere beneath, it cracks and breaks, forming
lithospheric plates. The movement of these plates drives earthquake and volcanic
activity
Why is Crust not melted - CORRECT ANSWER-The outermost portion of the
lithosphere, the crust, is the part of Earth we walk on and that the atmosphere and
oceans rest on. The crust is not melted by Earth's internal heat because it is in contact
with the atmosphere and oceans, which are relatively cold. Although Earth's crust
makes up about 1% of Earth's volume, it is very important to people.
Continental Crust - CORRECT ANSWER-makes up the continents. It is composed
mainly of granite, a silica-rich rock made up of coarse grains.
Oceanic Crust - CORRECT ANSWER-lies beneath the oceans and is composed mainly
of basalt, a dark, heavy, fine-grained volcanic rock.
Magma - CORRECT ANSWER-is melted rock that is below the surface of the crust.
Chemically, granite is composed chiefly of silica, aluminum, potassium, calcium, and
sodium. It is light in both weight (2.7 g/cm3) and color compared with basalt, which
weighs about 3 g/cm3
Lava - CORRECT ANSWER-magma that spills onto the surface of Earth's crust.
Chemically, basalt (made of Lava) is composed mostly of compounds of silica that are
BRAINSCAPE1
GEOS Midterm Exam with complete
solutions latest version
The five mass extinctions in Earth's history were caused by many factors - CORRECT
ANSWER-including periods of intense volcanic activity, global climate change, and
asteroid impacts.
Geological Time Chart - CORRECT ANSWER-Collectively Earth's first three eons, the
Hadean Eon, Archaean Eon, and the Proterozoic Eon, constitute 88% of Earth's history.
The top of the diagram shows the present day, and the lower parts of the diagram show
increasingly older times. Our current eon, the Phanerozoic Eon, comprises 12% of
Earth's history. Nearly all major evolutionary events of Earth history have happened in
the Phanerozoic. (B) The Phanerozoic Eon, shown in detail here, is subdivided into
numerous eras, periods, and epochs. We live in the Holocene Epoch, which is nested in
the Quaternary Period, which in turn is nested the Cenozoic Era of the Phanerozoic
Eon. Note that the Anthropocene Epoch is not included above the Holocene epoch
because scientists have not yet formally recognized it as a new epoch. (C) In this
graphic, Earth's entire history is compressed into a single year of time, with Earth and
the solar system forming on January 1 (at the bottom of the graphic) and the present
day being midnight on December 31. Each month on the calendar represents about 383
million years, and each second is about 145 years. Using this perspective, we can see
that most life-forms we are familiar with arose only recently, no earlier than mid-
"November" (kya = thousand years ago; mya = million years ago; bya = billion years
ago).
Uniformitarianism - CORRECT ANSWER-is the principle that the same gradual and
nearly imperceptible processes operating now have operated in the past.
Relative age - CORRECT ANSWER-compares the age of one object or event with the
age of another, without specifying how old either object is.
Relative age accounts for - CORRECT ANSWER-the order of events. For example, if
two trees are growing side by side and one is smaller, we might reasonably conclude
that the smaller tree is younger. We may not know how old it is in absolute terms but
only that it is younger relative to the larger tree.
BRAINSCAPE1
, BRAINSCAPE1
Apply Relative Age to Earth - CORRECT ANSWER-This concept can be applied to rock
layers in Earth's crust. A sequence of rock layers forms as layers of sediments are
deposited, one after another, and eventually harden into sedimentary rock
Absolute age - CORRECT ANSWER-is specified in years before the present
Absolute age Techniques - CORRECT ANSWER-which is given in actual numbers of
years, is determined using various dating techniques. For example, tree-ring analysis
(called dendrochronology) provides absolute ages of trees. Most trees create one new
growth ring each year. Counting the growth rings in a cut tree allows an investigator to
determine the absolute age of a tree.
radiometric dating or half-lives - CORRECT ANSWER-which involves using unstable
atoms in materials to assign ages to those materials. Radiometric dating methods,
which have been in wide use since the 1950s, provide a means by which we can
determine the absolute ages of ancient materials such as rocks, wood, and bones.
These methods are based on the premise of radioactive decay: Unstable atoms (called
parent atoms) found in some elements decay (convert) to a stable element (called
daughter atoms) at a constant rate through time. For example, the parent atom carbon-
14 decays into the stable daughter atom nitrogen-14. Young objects that contain an
unstable atom have high proportions of that parent atom because there has not been
enough time for the parent form to decay to the stable, daughter form. In very old
objects, the unstable parent atom is largely gone, having decayed to its stable form. The
time it takes for half of the parent atoms to decay to the daughter atoms is called a half-
life.
As depth increases, so does temperature; this pattern is called the geothermal gradient.
- CORRECT ANSWER-Geothermal Gradient
Factors that have created and continue to create hot earth interior - CORRECT
ANSWER-Two factors have created and continue to create a hot Earth interior:
radioactivity and friction. The most important source of Earth's internal heat is
radioactive decay of unstable elements, mainly potassium, uranium, and thorium. These
elements give off heat during the decay process.
In addition to radioactivity, friction has played and continues to play a role in heating
Earth's interior. When the Moon first formed, it was only about 24,300 km (15,000 mi)
away from Earth (compared with today's average distance of 384,399 km [238,854 mi]).
Because it was so close, the Moon's gravitational pull exerted enormous lunar tidal
forces, which distorted Earth's shape and created heat from the friction of the movement
of Earth's interior. Although it is farther away today, the Moon still exerts tidal forces on
Earth, distorting its shape, and creating a small amount of heating through friction. -
CORRECT ANSWER-
seismic waves - CORRECT ANSWER-energy released by earthquakes that travels
through Earth's interior. One way we know earth's behaviours.
BRAINSCAPE1
, BRAINSCAPE1
An earthquake - CORRECT ANSWER-is a sudden shaking of the ground caused by
movements of Earth's crust. We also have other direct and indirect evidence related to
Earth's internal structure
Earth's Layers - CORRECT ANSWER-The heaviest and most dense layers and the
greatest pressures are found at Earth's center. Outward from the center, the density of
rocks and the pressure decrease. The atmosphere and oceans are a continuum with
the solid Earth. Each layer is made of matter in solid, liquid, or gaseous states. It is no
accident that the layers are arranged this way—from most dense to least dense. As
Earth accreted from dust and gas during the formation of the solar system, the densest
materials settled deepest, and the least dense materials, like gases and water, rose to
the surface.
superposition principle - CORRECT ANSWER-states that in such a sequence of rock
layers, the oldest rocks are at the bottom, and the youngest rocks are at the top
The inner Core - CORRECT ANSWER-which extends from Earth's center to about
5,150 km (3,200 mi) below Earth's surface, is a mixture of dense elements, mostly iron
and nickel. Inner core temperatures approach 6,000°C (10,800°F). These temperatures
would melt the inner core if not for the extremely high pressure found there. The
extreme pressure in the inner core keeps the inner core solid. Atoms in molecules are
forced closer together under great pressure. As a result, to break molecular bonds and
melt rocks in the inner core, temperatures must be very high; temperatures need not be
as high to melt rocks at or near Earth's surface, where there is much less pressure.
The Outer Core - CORRECT ANSWER-surrounds the inner core, is composed of a
liquid alloy of iron and nickel. Temperatures in the outer core begin around 4,000°C
(7,232°F) and increase toward the inner core. The outer core extends to about 2,900 km
(1,800 mi) below Earth's surface. The outer core is liquid because pressures within it
are less than the pressure in the inner core; lower pressure allows the outer core to melt
and flow. This circulating liquid metal generates electrical currents and creates Earth's
magnetic field. Together, the inner and outer core make up about 15% of Earth's
volume.
Magnetosphere - CORRECT ANSWER-Earth's magnetic field forms the
magnetosphere, which surrounds the planet and shields it from the solar wind, a stream
of electrically charged particles emitted by the Sun
Lower Mantle - CORRECT ANSWER-the layer of heated and slowly deforming solid
rock that lies between the base of the crust and the outer core. The lower limit of the
lower mantle lies 2,900 km (1,800 mi) below the surface; it extends upward to
approximately 200 km (125 mi) below the surface. Temperatures in the lower mantle
range from about 4,000°C (7,232°F) near the outer core to about 1,000°C (1,832°F)
toward the crust.
BRAINSCAPE1
, BRAINSCAPE1
Even though the lower mantle is solid rock, it is not rigid and unmovable. Instead, it
slowly deforms and flows at a rate of about 15 cm (6 in) per year. When a solid is able
to deform and flow, its behavior is described as plastic (or ductile). Warm (but unmelted)
candle wax or beeswax is plastic in that it can be squeezed and shaped with your
fingers once it is warmed. - CORRECT ANSWER-Movement of lower mantle
The asthenosphere - CORRECT ANSWER-(from the Greek for "weak") is the layer of
the mantle found between depths of about 100 and 200 km (62 and 124 mi). It gets its
name from the fact that it is softer and weaker than the lower mantle beneath it. Like the
lower mantle, this layer of rock is solid but can flow under pressure. There is
considerably less pressure in the asthenosphere than in the lower mantle below it. As a
result, although the rocks here are still in a solid state, they are nearer to melting and
are consequently weak and easily deformed.
Upper Mantle Makeup - CORRECT ANSWER-The asthenosphere and the lithospheric
mantle (discussed next) together make up the upper mantle. The lower mantle and
upper mantle together make up the mantle, which accounts for about 84% of Earth's
volume. The mantle is composed of silicate rocks (made mostly of minerals that contain
silica) that are rich in iron and magnesium.
The Lithosphere - CORRECT ANSWER-relatively strong and consists of Earth's rigid
crust and the rigid lithospheric mantle beneath it, extending to a depth of about 100 km
(62 mi) on average (see Figure 12.11). Unlike the asthenosphere and lower mantle, the
lithosphere is not plastic and does not deform and flow. Instead, when subjected to
stresses from the moving asthenosphere beneath, it cracks and breaks, forming
lithospheric plates. The movement of these plates drives earthquake and volcanic
activity
Why is Crust not melted - CORRECT ANSWER-The outermost portion of the
lithosphere, the crust, is the part of Earth we walk on and that the atmosphere and
oceans rest on. The crust is not melted by Earth's internal heat because it is in contact
with the atmosphere and oceans, which are relatively cold. Although Earth's crust
makes up about 1% of Earth's volume, it is very important to people.
Continental Crust - CORRECT ANSWER-makes up the continents. It is composed
mainly of granite, a silica-rich rock made up of coarse grains.
Oceanic Crust - CORRECT ANSWER-lies beneath the oceans and is composed mainly
of basalt, a dark, heavy, fine-grained volcanic rock.
Magma - CORRECT ANSWER-is melted rock that is below the surface of the crust.
Chemically, granite is composed chiefly of silica, aluminum, potassium, calcium, and
sodium. It is light in both weight (2.7 g/cm3) and color compared with basalt, which
weighs about 3 g/cm3
Lava - CORRECT ANSWER-magma that spills onto the surface of Earth's crust.
Chemically, basalt (made of Lava) is composed mostly of compounds of silica that are
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