Astronomy Ch 6 - The Earth

Select all of the objects that cannot be pulled into a spherical shape by gravity, if found out in space.

A typical asteroid in the asteroid belt. The icy nucleus of a comet.

Which ancient Greek scientist argued that Earth was a sphere due to the jostling of its material?

Aristotle

By what process did the early Earth gain enough heat to differentiate?

Bombardment by planetesimals Decay of radioactive materials

What causes an aurora?

Charged particles from the Sun interact with our magnetic field, exciting ions in Earth's atmosphere, which then emit light.

In convection, why does cooler material sink?

Cooler material is more dense than hotter material, allowing it to sink.

Match Earth's layers to the labels.

D - Solid core C - Liquid outer core B - Mantle A - Crust

Match the information about Earth's interior with the observations to determine it.

Dense core - Earth's average density is 5.5 g/cm3, but the density of the surface rocks is about 3 g/cm3. Iron in core - Iron is common in the crust and has a density of 7.9 g/cm3. Liquid layer present - S waves don't reach every part of Earth's surface. Density increases depth - Seismic waves' travel through Earth varies.

Why is iron concentrated in the core of Earth?

Differentiation resulted in iron sinking to the core when the early Earth was molten.

Why is Earth's mantle molten and its outer core liquid, while this is not true of the Moon or Mars?

Earth formed hot and has a high ratio of volume to surface area. Long-lived radioactive elements are in Earth in large quantities.

Match the features or events with how plate tectonics causes them.

Earthquakes - Plates shift abruptly at boundaries. Continents move - Convection in the mantle drags Earth's surface. Volcanoes on the northwest coast of the United States - Ocean plates are subducted at plate boundaries. Mountain ranges - Ocean plates collide with continental plates,wrinkling the crust.

Select all the choices that describe Earth's mantle

Essentially solid but can flow Mostly olivine (a mineral of Fe, Mg, Si, and O)

Select all the observations that lead us to believe that Earth's interior is hot

Every 100 m we dig into Earth, the temperature goes up 2 K. Earth has active volcanoes.

True or false: The Van Allen belts trap radioactive particles

False - (they trap charged particles from the Sun)

True or false: The Van Allen belts trap radioactive particles.

False - (they trap charged particles from the Sun)

Select all the features or events caused by plate tectonics.

Folded mountains Earthquakes The Atlantic Ocean getting wider New crust is formed.

Both Earth and the asteroid Gaspra are made of the same materials. Earth is spherical, but Gaspra is not. Why?

Gaspra has a very low mass Earth is a large, very massive body

___ is the force that pulls Earth into a nearly spherical shape.

Gravity

Which of the following is the oldest civilization known to have understood Earth is a sphere?

Greece - (Ancient Greeks could see the round shadow of Earth upon the Moon during lunar eclipses)

Mars is about one and a half times farther from the Sun than Earth is. Which of the following could raise the surface temperature of Mars?

Having a denser atmosphere, especially with greenhouse gases

In convection, why does heated material rise?

Heating decreases density, causing that material to float upward

Mars spins at nearly the same rate as Earth, but is much smaller in diameter and lower in mass. Why does it have a much weaker magnetic field than Earth? Select all that apply.

It has cooled off inside. It has a much smaller iron core.

Select all of the following that correctly describe how water vapor behaves in Earth's atmosphere.

It is found almost exclusively in the troposphere. It can form tiny ice crystals. It helps remove carbon dioxide from the atmosphere.

What is happening to Earth's magnetic field?

It is getting weaker and might eventually reverse.

Why is Earth's outer core liquid?

It is hot enough to melt iron

Venus has nearly the same mass and diameter as Earth and spins much more slowly. Select all that explain why it has a much weaker magnetic field.

It spins too slowly

Match the planet with its likely composition.

Mercury : Iron Mars : Mostly rock, possibly a little iron Saturn : Ices & gas Uranus : Ices & rock

How can we know that Earth's magnetic field has reversed directions over Earth's history?

Minerals in lava preserve the orientation of Earth's magnetic field at the time the lava solidified.

Select each of the following that contribute to the process of recording reversals of Earth's magnetic field in rocks.

Molten lava solidifies into solid rock with its internal magnetic field aligned to Earth's field. Sea floor is formed when molten rock rises at a mid-ocean ridge. The sea floor spreads when plate motions pull pieces of it in opposite directions. The distance of a piece of sea floor from the ridge indicates its age.

Select the correct descriptions of Earth's outer core

Mostly iron and nickel Liquid (flowing) About 2300 km wide

Plate tectonics is supported by a large body of evidence. Select all that are evidence of plate tectonics.

New crust forms at rifts, and earthquakes, mountains, and volcanoes occur near subduction zones. GPS measurements show continental plates move several centimeters per year. Fossils found along the coastline of Africa match those found in South America.

Match the components in the atmosphere with their approximate percentage by volume.

Nitrogen - 78% Oxygen - 21% Water vapor - a few percent Carbon dioxide - less than 0.1% Argon - about 1%

Match the amount of a radioactive element that remains after the number of half-lives.

One half-life - 1/2 Two half-lives - 1/4 Three half-lives - 1/8 Six half-lives - 1/64

255 million years ago, all the continents were joined in a landmass called

Pangaea

Match the terms to their definitions.

Radioactive decay - The spontaneous breakdown of unstable atomic nuclei into smaller nuclei Radioactive dating - A procedure by which scientists measure the age of a sample based on the ratios of parent and daughter atoms Daughter atom - A product of radioactive decay, which may or may not be radioactive itself Half-life - The average length of time for half of the radioactive particles to decay

____ generate(s) heat in Earth's interior, much as happens in a nuclear reactor

Radioactive elements

Seismic waves come in two forms, ____ and ____

S (secondary) P (primary)

___ waves, which travel through Earth and can be detected all over the world, are generated by earthquakes.

Seismic

Match each type of material with its typical density.

Silicate rock - About 3 g/cm3 Water or ice - About 1 g/cm3 Iron - About 7.9 g/cm3

Match the feature of the inner core to its cause or the evidence for it

Solid rather than liquid or gas - Too much pressure to be anything else Made of iron and nickel - The densest materials sink to the core Radius is about 1200 km - Seismic wave detection patterns

Select all of the following that describe the Van Allen radiation belts.

The belts are caused by Earth's magnetic field. The belts are dangerous to humans. The belts are doughnut shaped regions around Earth.

What would happen to the shape of Earth if it were to stop spinning?

The bulge would go away, making it more spherical.

Select all the answers that correctly describe changes in Earth's magnetic field.

The changes occur roughly every 250,000 years. Changes in Earth's magnetic field explain the stripes of opposite polarity on the ocean floor. The magnetic field hasn't changed direction in about 780,000 years.

Why does Earth have an equatorial bulge?

The rotation of Earth causes material near the equator to move away from Earth's rotational axis.

Earth's north magnetic pole is located high in the Northern Hemisphere, although it is offset from the north rotational pole. If your compass needle is pointing toward the North Pole, which pole of the compass is pointing north?

The south pole

Select all that happen to charged particles from the Sun when they encounter Earth's magnetic field.

They move in spirals around the magnetic field lines and can create auroras. Many are trapped in the Van Allen belts. Some are deflected by the magnetic field and go around Earth.

Match the layers of Earth's atmosphere to their descriptions.

Troposphere - The lowest layer of Earth's atmosphere; water vapor circulates, causing weather. Stratosphere - From 12 km to 50 km, this stable layer includes the ozone layer. Ozone layer - This layer absorbs ultraviolet light.

True or false: Volcanic eruptions show us that Earth's interior is hot

True

Why does humid air (rich with water vapor) tend to rise up in the atmosphere.

Water vapor weighs less than most of the other molecules in the atmosphere.

The choices each represent a property of P or S seismic waves. Select the properties of S waves.

Wave motion is perpendicular to direction of travel. Travel more slowly than the other

Over time, Earth's rotation has slowed. Earth is spinning a little more slowly today that in the past. Therefore, we can logically conclude ____

a person on the equator is moving a little more slowly today than they would have in the past Earth's equator bulges slightly less today than in the past

Lines representing a magnetic field ____

always run from one pole to the other (e.g., north to south)

Earth's magnetic poles and rotational poles ____

are separated by a few degrees, and the magnetic poles slowly wander

A trans-Neptunian object (TNO) and an asteroid have the same volume, but the mass of the asteroid is three times as much as that of the TNO. Therefore, we expect the density of the asteroid to be _____ times _____

bigger 3

Earth has a ___ radius at the equator than at the poles as a result of ___ and ___

bigger inertia, spinning, or rotation inertia, spinning, or rotation

We can find the number of years since a rock solidified by ____

comparing the amounts of radioactive elements with their daughter elements

The circulation of material shown in the image is best described as ___

convection

Earth's magnetic field is the result of ____

convection currents in the molten iron core

Traveling upward from Earth's surface through the layers of atmosphere, the temperature ___ through the troposphere, then ___ through the stratosphere.

decreases increases

Young planetary cores were frequently melted by the kinetic energy of impacts with planetesimals as the Solar System formed. The separation of materials by density in these melted planets is called ___

differentiation

Magnetic lines of force ____

emanate from one end of a magnet and loop around it, returning to the other end show the direction that compass needles would point are imaginary lines used to depict the shape and strength of a magnetic field

The surface area of a spherical planet is 4πR2. The volume is V = 4343πR3. The ratio of the surface area to volume (3R)3R determines how fast a body loses heat (the smaller the ratio, the slower the heat loss). As a planet's radius increases, the ratio ____.

gets smaller by the same factor

Venus has almost the same size and density as Earth. Is it likely to have a solid inner core as well?

it will have nearly the same pressure squeezing down on its core as Earth does.

Electrical currents in the molten (outer) iron core of Earth create Earth's ___ field.

magnetic

The average density of an object, ρ, is its ____.

mass / volume

To find the average density of a planet, we need to find the planet's ____

mass and radius - (The average density is the mass divided by the volume [found from the radius] )

Which of the following techniques can be used to study Earth's interior?

measure the speed of earthquake waves compute the average density of the planet

Earth's magnetic poles ________

migrate slowly over the years reverse occasionally

Silicates at Earth's surface are composed primarily of ____

oxygen silicon

The most common element in Earth's crust, by mass, is ____

oxygen - (Oxygen in the crust is in compounds with other chemicals, most commonly bonded with silicon to form silicates)

Most continental mountain ranges on Earth are formed where ____.

plates collide and wrinkle

The ___ of a magnetic field determines which direction is "north" and which is "south."

polarity

Rocks, more technically referred to as compounds of oxygen and silicon called ___ are the most common materials in Earth's crust.

silicates

What is the composition of Earth's mantle?

silicates

It is more difficult to breathe on top of a mountain because ____

the density of the air is much lower than at sea level

Convection in the mantle can occur because ____

the material in the mantle can flow. Material heated by the core can rise

Plate tectonics describes ____

the motion of large, stable sections of Earth's crust

When a planetesimal struck the early Earth, the collision converted gravitational potential energy into ___ energy.

thermal

The greenhouse effect ____

traps infrared radiation in the atmosphere is stronger when there is more water vapor and carbon dioxide in the atmosphere slows the rate at which energy that heats Earth is lost (radiated into space)

Rain droplets form from water vapor that condenses at low temperature and then capture atmospheric carbon dioxide as they fall toward the ground. This process is at work in the ____ where most of Earth's atmospheric water vapor is found

troposphere

The majority of Earth's atmosphere is found in the ____

troposphere

The "plate" in "plate tectonics" refers to ____

very thin, very broad pieces of Earth's crust

Arrange these items by density, from lowest (top) to highest (bottom).

1. A hot air balloon 2. An acorn 3. A water balloon 4. A slab of concrete 5. A gold wedding ring

Put the layers of Earth in order from the exterior (top) to the interior (bottom).

1. Crust 2. Mantle 3. Liquid Core 4. Solid Core

Bodies retain heat as a function of the ratio of surface area to volume; the smaller the ratio, the slower heat is lost. Assuming the planets shown are terrestrial bodies that formed in the usual way, rank them from the one with the hottest core (top) to the coolest core (bottom).

1. D 2. B 3. C 4. A

Water vapor warmed by the surface of Earth contributes to the removal of carbon dioxide from the atmosphere. Arrange the choices to explain how.

1. Humid air rises to altitudes where the temperature is very low 2. Water vapor condenses into droplets and begins to fall as rain 3. Carbon dioxide dissolves into water droplets 4. Water droplets are absorbed into the ground or fall into bodies of water

Rank these materials based on their abundance in Earth's atmosphere, with the most common material at the top.

1. Nitrogen 2. Oxygen 3. Argon 4. Carbon dioxide 5. Hydrogen

List the following elements in order from most common to least common in Earth's crust

1. Oxygen 2. Silicon 3. Iron 4. Hydrogen

The idea of continental drift was suggested as early as the 1800s, but the theory of plate tectonics was not accepted until the 1960s. Rank these examples of evidence supporting the theory from the weakest (top) to the strongest (bottom).

1. Some continents seem to fit together like puzzle pieces 2. similar fossils are found on either side of the Atlantic ocean 3. studies show that widely separated eroded mountains were once part of the same systems 4. today GPS systems allow us to measure that plates move a few centimeters per year

Create a subsea rift by placing the following steps in their proper order, from start to finish.

1. mantle material is heated deep within earth 2. heated material rises pushing existing material up and sideways 3. adjacent plates are driven apart 4. mantle material seeps between plates forming new crust

Describe the process of plate subduction and the creation of a mountain range by arranging the statements in a sensible order.

1. mantle material is heated deep within earth and rises 2. new crust forms at the mid-oceanic ridge pushing the plate sideways 3. at the other edge an ocean plate is driven below a continental plate 4. the interaction wrinkles the continental plate

Put the steps in order to follow the path of energy that heats Earth through the greenhouse effect.

1. visible sunlight is absorbed by earths surface warming it 2. Earth emits blackbody radiation with a peak in the infrared 3. CO2 and H2O in the atmosphere absorb infrared radiation 4. The absorbed infrared light is reradiated some toward space and some toward earth further heating it 5. Earth is now receiving sunlight and the light from the atmosphere earth gets hotter

The asteroid Ceres has a mass of 9.4 × 1020 kg and a volume of about 4.7 × 1020 L (liters). It has an average density (ρ = MVMV) of about ____.

2 kg/L

The half-life of potassium-40 is about 1.3 billion years. If a rock containing 200,000 atoms of potassium-40 was formed 3.9 billion years ago, today we would expect it to contain ___ thousand atoms of potassium.

25

About how many million years ago were all Earth's continents formed together into a single supercontinent?

250

Rounded to the nearest whole number, the density of ordinary rock is about ___ g/cm3. Water is 1 g/cm3

3

Match the type of material displacement with the type of wave. The waves are traveling to the right along the spring.

A - P wave B - S wave

Which of the following is evidence for global warming?

A clear correlation between carbon dioxide levels and Earth's temperature

Select all of the objects that would be pulled into a spherical shape by gravity, if found out in space.

A house-sized pool of water A solar system-sized cloud of gas

Which statement best describes magnets and magnetic fields?

A magnet always has a north pole and a south pole.

____ occurs when two tectonic plates pull apart (or the plate breaks and pulls apart), and mantle rock rises up into the gap to form new crust. This often happens in the middle of the oceans.

A rift valley Rifting