the effect of the moon on tides - telecom...

Name:_____________________________________________________

Read each article. Then, create the following thinking maps to go with the articles:

Article 1: Ocean Tides

Create a DOUBLE BUBBLE MAP that compares and contrasts the effect of the sun on tides and the effect of the moon on tides. (ADD BUBBLES AS

NEEDED)

Tree Map: Create a TREE MAP that classifies the four different types of tides. Be sure to DESCRIBE each tide briefly underneath. The first one is done

as an example.

The effect of the sun on tides

The effect of the

moon on tides

Types of Tides

Spring Tide

Higher than normal

high tide, affected by

the sun-during new

moon or full moon

Article 2: The Ocean Conveyor Belt

Currents

CURRENTS

TYPES OF CURRENTS

CAUSES OF CURRENTS

IMPORTANCE OF CURRENTS

EXAMPLES OF CURRENTS

Create a CIRCLE MAP that defines what currents are, using infor-

mation from the article.

Fill in the TREE MAP with information from the article to support/describe/elaborate on each branch

First,

Create a FLOW MAP that details the steps of how an ocean freezes.

Next,

Then,

Finally,

Name:_____________________________________________________

Read each article. Then, create the following thinking maps to go with the articles:

Article 3: “The Big One” by sea and not by land

Create a DOUBLE BUBBLE MAP that compares and contrasts the San Andreas Fault with the Cascadia Fault. ADD BUBBLES TO THE MAP.

Tree Map: Create a TREE MAP that explains why the Cascadia

Fault is dangerous. USE INFORMATION FROM ARTICLE.

San

Andreas

Fault

Cascadia

Fault

Reasons why Cascadia Fault is Dangerous

Create a BUBBLE MAP describing

Tsunamis. ADJECTIVES ONLY. Each

bubble should have ONE word, a

“describing word” (Example given)

Tsunamis

BIG

Article 4: Ridges and Trenches

Create a DOUBLE BUBBLE MAP that compares and contrasts RIDGES and TRENCHES. (ADD BUBBLES AS NEEDED)

Tree Map: Create a TREE MAP that classifies the four different types of tides. Be sure to DESCRIBE each tide briefly underneath. The first one is done

as an example.

RIDGES TRENCHES

Evidence of How Mid-Ocean Ridges Form

1

Ocean Tides

6E3BD Atmosphere, Water Cycle, Waves, and Currents

Earth and Space

1 The gritty sand oozes between your toes as you

stroll along the beach. The gentle lapping of the

waves lulls you into a peaceful state. The ocean

water appears to stretch its cool fingers farther up

onto the shore than it did earlier in the day. Is it

your imagination or is the water level rising?

2 Well, you may feel better knowing that it is not your

mind playing tricks on you. Throughout each day,

the ocean water rises and falls at different times.

This movement of water is known as a tide. A tide

is a change in water level at the shoreline; it is being caused by the pull of gravity between

Earth and the Moon and Earth and the Sun. During each 24-hour period, the beach will

experience two high tides and two low tides in most places around the world. Periodically,

the beach will also experience a spring tide and a neap tide.

3 How does the gravity between the Moon and Earth cause a tide? Each day, the beach can

expect a high tide, a low tide, another high tide, and then another low tide. Between each of

these tides is approximately six hours. This is important to know because each quarter turn

of Earth takes six hours. Earth will make four quarter turns in a 24-hour period. With each

turn, the Earth and the Moon will be in different positions. These positions determine if it is a

high or low tide. These tides are a direct effect of the Moon's gravity tugging on the water on

Earth.

4 The Moon's gravity has a powerful effect on Earth's waters. In fact, it is far more powerful

than the Sun's effect. Why, you ask? It is because the Moon is closer to Earth than the Sun.

The Moon pulls the water that is on the side of Earth facing the Moon toward itself in a big

bulge. At the exact same time, on the side of Earth that is facing away from the Moon,

another bulge is forming. These two places will experience high tides. The opposite places

on Earth, which are not facing toward or away from the Moon, will experience low tides. As

Earth keeps making quarter turns, the tides change from high to low and low to high.

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2


Earth and Space

5 How does the Sun affect the ocean tides? As mentioned before, the Sun has less of an

effect on the tides. However, the gravitational tug of the Sun can increase a high tide by

making it rise higher than normal. This is known as a spring tide. A spring tide has

absolutely nothing to do with the season spring. A spring tide happens when the Moon is

either in its new moon or full moon phase. The Moon, Sun, and Earth line up perfectly with

one another. This allows their gravitational pull on the ocean to work together making the

high tide rise higher.

6 A neap tide is the opposite of a spring tide. A neap tide is a lower than normal high tide. At

the same time, there is also a higher than normal low tide. This happens as the Moon

enters a first and last quarter moon phase. At this time, the Sun and the Moon are in

positions that form a right angle to one another. The gravitational pull of the Sun pulls

water away from the bulge formed by the Moon at high tide. The water moves toward the

places that are having low tides. This results in a low high tide and a high low tide.

7 In a 24-hour period, a beach will have two high tides and two low tides. When the Moon is

new or full, it will line up with the Sun and Earth causing a spring tide. When the Moon and

the Sun form a right angle to one another, there will be a neap tide. The next time you visit

a beach, pay attention to the water level on the shoreline. You might just experience a high

or low tide yourself. As you do, remember that the gravitational pull of the Moon is what is

causing the ocean tides.

3

1 Which statement best describes what an ocean tide is?

A A change in water level that makes a high tide higher

B A change in water level at the shoreline that is being caused by the

gravitational pull of the Moon

C A change in water level at the shoreline that is being caused by the

gravitational pull of the Sun

D A change in water level that makes a low tide lower

2 What effect does the Sun have on the ocean tides?

A The Sun does not have an effect on the ocean tides because it is too far

away.

B The Sun warms the water causing it to rise.

C The gravitational pull of the Sun causes spring and neap tides.

D The gravitational pull of the Sun's gravity is more powerful than the Moon's.


Earth and Space

4

3 During a spring tide, the Moon is either in its new moon or full moon phase. What

effect does this have on an ocean tide?

A The Moon, Sun, and Earth line up perfectly with one another, allowing their

gravitational pulls to work together and making the high tide rise higher.

B The Moon and Sun are positioned at a right angle to one another causing a

lower than normal high tide. The Sun warms the water causing it to rise.

C In most places, the beach will experience two high tides and two low tides.

D A spring tide only happens during the springtime.

4 How does the gravity between the Moon and Earth cause the tides to rise and

fall?

A The position of the Sun interferes with the Moon's gravity.

B During each quarter turn that Earth makes, the Moon and Earth line up in

different positions allowing for the high and low tides.

C Earth makes four quarter turns each day causing spring and neap tides.

D The gravity of the Moon is stronger at night than during the day.


Earth and Space

5

5 What is the main point of paragraph 3?

A Solar flares affect the tides.

B Tides are not affected by the Moon's orbit.

C The neap tide is the opposite of the spring tide.

D Gravity between the Moon and Earth causes different tide levels.


Earth and Space

The Ocean Conveyor Belt

1 Water in the ocean is always

moving. Waves break the surface.

Currents move in the shallows and

in the depths. Currents near the

surface are mainly caused by the

winds and tides. Deep water

currents run on a different engine.

2 Currents run through all of the

Earth’s oceans. They are important

for several reasons. The currents

help keep global temperatures even. They move energy around the oceans. Otherwise, the

3 Currents also cycle nutrients through the ocean. Water near the surface is rich in oxygen.

Deep waters are rich in nutrients. When sea creatures die, they sink to the ocean bed. They

decay and release nutrients into the deep water. There must be a way to mix and exchange

the two. In fact, there is—a slow global deep water current. Wallace Broecker is a noted

oceanographer. Broecker named this the ocean conveyor belt.

4 Deep ocean currents are caused by thermohaline circulation. What does this mean? Well,

“thermo-” means temperature. And “-haline” means salt. But how do temperature and salt

cause currents? The linking factor is density.

5 Density is a physical property of all materials. It is the measure of how much mass the

material has for a standard particular volume, generally 1 cm3. Whether something sinks or

floats on a liquid is based on its density. A more dense substance, either liquid or solid, will

sink to the bottom. A less dense substance will be found on the top. Water is more dense as

a liquid than as a solid. This is why ice floats. Liquid water can vary in density. As long as it

remains a liquid, water gets more dense as it gets colder. Also, water’s properties change

based on how much salt is dissolved in it. The measure of salt in a water sample is called

salinity. Water gets more dense as its salinity goes up.

6E3A Earth’s Water

Earth and Space

1

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equator and tropics would get too hot. The poles would get too cold. While deep water

currents do play a part in energy transfer, this is mainly done by surface currents. These are

currents in the top 100 meters of the ocean. Their main driving force is the wind. They flow

quickly and form giant circles. One example is the Antarctic Circumpolar Current, which

forms a giant ring around the continent of Antarctica.

6 There are three special places on Earth where conditions are right to pump the ocean

conveyor belt. Two are in the North Atlantic Ocean. The other is the Weddell Sea off the

coast of Antarctica. All three locations lie near either the north or south Arctic Circle. On the

map at the top of this passage, these locations are labeled “deep water formation.”

Conditions are right in these places to make water very, very dense. It will sink to the bottom

of the ocean. But how does this happen? We will focus on the Weddell Sea for the answer.

Remember that a similar process happens in the North Atlantic to form deep water.

7 During the winter months, air temperatures in Antarctica are very cold. Areas surrounding

Antarctica get very little sunlight for much of the winter. Moving closer to the South Pole,

some areas get no sunlight at all for weeks. Very cold winds from the interior of the Antarctic

continent blow away from the South Pole. At the Weddell Sea, local geography funnels

these winds over the surface of the water. The Weddell Sea is fringed year round by ice

sheets. Conditions are much colder in the winter. Sheets of ice form rapidly. Much of the sea

has seasonal ice coverage. This rapid ice formation is one piece of the puzzle. The strong

icy winds are another.

8 When ice forms from salt water, an interesting thing happens. The ice that forms is pure

water. The salt gets left behind. (This works as long as some of the water remains liquid.) In

the Weddell Sea, there is rapid formation of lots of pack ice. Much of the salt is left behind.

This leads to water with very high salinity. There is another interesting property of water. As

the salinity of a water sample goes up, its freezing point goes down. This means that very

salty water will stay liquid below the freezing point of fresh water. The icy winds cool the

water, often to -1°C (30°F). The winds turn this high salinity water into the coldest,

densest water in Earth’s oceans. It sinks. This forms the Antarctic Bottom Water. The other

two locations form slightly less dense North Atlantic Deep Water.

9 The sinking of the newly formed deep water pushes the water from previous years. This

drives the slowly moving ocean conveyor belt. The Antarctic Bottom Water forms a current

that travels around the continent of Antarctica. The North Atlantic Deep Water slowly creeps

south to join these currents. Portions of the giant current break off. They travel along the

bottom of the Indian and the Pacific Oceans. The deep currents are shown in blue in the

image at the top of this passage. Finally, they will return to the surface. These upwellings

bring nutrients up to replenish surface water. Scientists think deep water may take between

600 and 1,000 years to return to the surface.


Earth and Space

2

1 What is the driving force of the deep water ocean conveyor belt?

A Winds push the deep water into the Pacific and Indian Oceans.

B Gravity from the Moon pulls the deep water toward the equator.

C The spinning of the Earth makes the deep water current run in circular

paths.

D Very cold temperatures create very dense water that pushes the deep

current along.

2 What is the meaning of circumpolar in paragraph 2?

A Circular path around the pole

B Wind-blown current

C Cold and salty

D Sinking


Earth and Space

3

4 Which location on the map above is a source of North Atlantic Deep Water?

A A

B B

C C

D D

Examine the map below. Use it to answer questions 3 and 4.


Earth and Space

4

3 Based on the information in the passage, which location on the map above marks

the Weddell Sea?

A A

B B

C C

D D

B

A

D

C

5 Which of these characteristics will produce the most dense water?

A High salinity, high temperature

B High salinity, low temperature

C Low salinity, high temperature

D Low salinity, low temperature


Earth and Space

5

"The Big One" by sea and not by land

Surfer Lee Johnson emerges from the water at San Onofre State Beach, Calif., with the twin domes from the San Onofre

Nuclear Generating Station in the distance. Officials have said the plant can sustain a 7.0 quake but not the 9.0 that

struck Japan in 2011. Photo: Mark Boster/Los Angeles Times/MCT

LOS ANGELES — Scientists worry that a strong earthquake off the coast of California

could do major damage to the West Coast.

Earthquakes on land can cause a lot of damage. But earthquakes in the ocean have their

own dangers. These earthquakes can cause a tsunami, a huge wave that rushes into

coastal cities.

The Cascadia fault line, 700 miles off the coast of Northern California, could produce a

tsunami that would heavily damage the West Coast, scientists say.

A giant tsunami along the West Coast would wash away towns, destroy U.S. Highway 101

and cause $70 billion in damage. The wave could destroy bridges, knock down power

lines, and cut communication systems like phones or Internet.

It’s possible that people would only have 15 minutes to escape. As many as 10,000 people

could die.

By Los Angeles Times, adapted by Newsela staff on 03.24.14

Word Count 629

Early Warning System

Officials in California, Oregon and Washington are now making plans to prepare for an

earthquake and tsunami. They hope to learn lessons from a 2011 disaster in Japan. A 9.0

earthquake there created a huge tsunami that flooded coastal areas.

That tsunami took people by surprise. It killed more than 10,000 and left more than

300,000 homeless. It also damaged a nuclear power plant. A meltdown at the plant spread

dangerous radiation in the area.

Researchers on the West Coast hope to save lives by quickly spotting a tsunami and

warning local citizens. They hope that new tsunami detectors deep under the ocean can

provide early warnings.

Predicting a tsunami’s strength is important to saving lives. Japanese scientists did not

realize how big their tsunami was. Local people were not prepared, and many lost their

lives.

It’s very important to have correct information, said Vasily Titov, head of the U.S. National

Oceanic and Atmospheric Administration's (NOAA) Center for Tsunami Research.

Escape To High Ground

To escape a tsunami, people must get to high ground such as a hill or mountain. But in flat

areas, there is nowhere to go. Safety officials must build high ground.

One idea is buildings with roofs that can protect people from a tsunami. One of these at a

school in Washington will protect 1,000 people with a high wall.

Officials have also discussed building man-made hills. Each hill could hold as many as

800 people.

California is famous for the San Andreas fault. This fault runs through the heart of the state.

It produced the famously scary 1906 San Francisco earthquake. The 1906 quake killed

more than 3,000 people.

Scientists now think that the Cascadia fault is more dangerous than they thought.

The Cascadia fault is made up of three tectonic plates that are pushing against each other.

The most powerful earthquakes in the last 10 years in California were caused by Cascadia.

Scientists had believed that the Cascadia fault could only produce a 7.5 earthquake. But

they now believe that it could create an enormous 9.0 quake.

Like A Rubber Band

The Cascadia fault is dangerous for two reasons. First, it is very long.

Second, it is an area where two huge tectonic plates are being pushed under the even-

larger North American plate. The smaller plates push under little by little, dragging the

North American plate down with them.

But the North American plate is old and strong, and it won’t be pulled down forever.

Once every couple hundred years, the North American plate snaps back upward like a

rubber band, creating a strong earthquake.

On March 16, a small earthquake caused by the Cascadia fault erupted 50 miles off the

coast, causing light shaking. No injuries or damages were reported.

The West Coast was spared this time, but scientists still wonder when “The Big One” will

hit.

“It could be today. It could be 100 years from now,” U.S. Geological Survey seismologist

David Oppenheimer said.

Quiz

1 What are two MAIN ideas of the article? Fill in the blank.

Scientists are worried that a strong tsunami on the __ fault line will cause a serious tsunami; we

can prepare by _.

(A) Cascadia; setting up tsunami warning systems and and building on high

ground.

(B) San Andreas; moving people to different cities that are safer and less prone

to earthquakes.

(C) Japanese; setting up sensors underwater to detect earthquakes and

tsunamis.

(D) Oregon; fundraising to pay for protective barriers and also to pay for

rebuilding destroyed areas.

2 Which of the following accurately summarizes the section "Like A Rubber Band"?

(A) The San Andreas fault is like a rubber band because the North American

plate gets pushed down and snaps back up every couple hundred years.

(B) The Cascadia fault is like a rubber band because the North American plate

gets pushed down and snaps back up every couple hundred years.

(C) The Cascadia fault is like a rubber band because there are a bunch of

tectonic plates knocking into one another constantly like bumper cars.

(D) The Cascadia fault is like a rubber band because it always produces the

world's largest earthquakes every 1,000 years.

3 According to the article, what is the relationship between earthquakes and tsunamis?

(A) Tsunamis typically occur in costal areas, and earthquakes occur in land-

filled areas.

(B) Earthquakes only occur in where there are mountains, and tsunamis occur

where warm water and air mix.

(C) An earthquake that occurs in the ocean may cause a huge wave, called a

tsunami, that can destroy coastal cities.

(D) An earthquake that occurs on land may cause a huge tsunami that can

destroy marine life far away from the shore.

4 Why are officials in California, Oregon and Washington interested in a 2011 disaster in Japan?

(A) The Japanese experienced a tsunami caused by an earthquake, which is

precisely what the West Coast is preparing for.

(B) Researchers on the West Coast hope to avoid what happened to the

Japanese by installing tsunami detectors.

(C) Both option A and B.

(D) Natural disasters that happen in Japan are always used by scientists to

predict natural disasters in other countries.

Answer Key

1 What are two MAIN ideas of the article? Fill in the blank.

Scientists are worried that a strong tsunami on the __ fault line will cause a serious tsunami; we

can prepare by _.

(A) Cascadia; setting up tsunami warning systems and and building on

high ground.

(B) San Andreas; moving people to different cities that are safer and less prone

to earthquakes.

(C) Japanese; setting up sensors underwater to detect earthquakes and

tsunamis.

(D) Oregon; fundraising to pay for protective barriers and also to pay for

rebuilding destroyed areas.

2 Which of the following accurately summarizes the section "Like A Rubber Band"?

(A) The San Andreas fault is like a rubber band because the North American

plate gets pushed down and snaps back up every couple hundred years.

(B) The Cascadia fault is like a rubber band because the North American

plate gets pushed down and snaps back up every couple hundred

years.

(C) The Cascadia fault is like a rubber band because there are a bunch of

tectonic plates knocking into one another constantly like bumper cars.

(D) The Cascadia fault is like a rubber band because it always produces the

world's largest earthquakes every 1,000 years.

3 According to the article, what is the relationship between earthquakes and tsunamis?

(A) Tsunamis typically occur in costal areas, and earthquakes occur in land-

filled areas.

(B) Earthquakes only occur in where there are mountains, and tsunamis occur

where warm water and air mix.

(C) An earthquake that occurs in the ocean may cause a huge wave, called

a tsunami, that can destroy coastal cities.

(D) An earthquake that occurs on land may cause a huge tsunami that can

destroy marine life far away from the shore.

4 Why are officials in California, Oregon and Washington interested in a 2011 disaster in Japan?

(A) The Japanese experienced a tsunami caused by an earthquake, which is

precisely what the West Coast is preparing for.

(B) Researchers on the West Coast hope to avoid what happened to the

Japanese by installing tsunami detectors.

(C) Both option A and B.

(D) Natural disasters that happen in Japan are always used by scientists to

predict natural disasters in other countries.

Ridges and Trenches

1 More than 100 years ago, geologist Alfred

Wegener made an interesting connection.

Wegener realized that the coastlines of

America and Africa fit together like a jigsaw

puzzle. Also, similar fossils are found on both

continents. He proposed that the continents

had once been joined. They had later drifted

apart. He did not know how this continental

drift happened. New technology was required

to discover the underwater ridges and

trenches that make continental drift possible.

2 Most scientific discoveries combine observation and inspiration. In the 1950s, Marie Tharp

and Bruce Heezen led a team of geologists. They made the first scientific map of the ocean

floor. They sailed around the ocean. They made many measurements of water depths. They

found a vast mountain range running along the middle of the Atlantic Ocean. They named it

the Mid-Atlantic Ridge. At first they thought that this ridge was unique to the Atlantic Ocean.

Later they found that ridges are in most oceans. These scientists discovered that mid-ocean

ridges existed. They still did not know how they formed.

3 Later studies by other scientists provided clues to how mid-ocean ridges form. Geologists

measured the magnetic properties of the ocean floor near the ridges. They found a pattern

of “stripes.” Rocks record the magnetic orientation of Earth at the time they are formed.

Earth’s magnetic field flips orientation every few million years. Therefore, the stripes

alternate. Importantly, the stripes are the same on both sides of the ridge. This suggests that

rock moves away from the ridge in both directions. Geologists found the age of rocks at

different distances from the ridge. Their data showed that younger rock is closer to the ridge.

Older rocks are found farther from the ridge. The last piece of evidence is from pictures of

ridges. The ridges show lava flows like those seen on volcanoes on land. These

observations led scientists to propose that seafloor spreading is part of continental drift. This

is also known as plate tectonics. The theory of plate tectonics explains how Earth looked in

the distant past. It explains many modern features. Plate tectonics allows us to predict how

Earth might look in the distant future.

4 We now know that the seafloor itself moves. It carries the continents with it. The entire crust

of Earth is divided into about 15 plates. These plates move on top of a semisolid mantle.

The movements are powered by convection currents. New crust forms at the mid-

1

6E3C Ocean Topography

Earth and Space

Lexile 760L

ocean ridges. It moves away from the ridges in both directions. The plates are moving away

from each other. Therefore, these areas are called divergent plate boundaries. Between 2

cm and 20 cm of new crust are formed at each mid-ocean ridge. A fissure in Earth’s crust

allows magma to erupt; it then cools into new crust. Eruptions and small earthquakes are

common along the 65,000 km of mid-ocean ridges encircling Earth. The formation of new

crust increases the distance between continents. It makes some oceans bigger.

5 New crust is being added continually at mid-ocean ridges. Doesn’t that mean that Earth is

always getting bigger? If addition of new crust were the only process at work, the answer

would be yes. Some scientists do think Earth is actually getting bigger. However, most

scientists think Earth stays pretty much the same size. To keep Earth at the same size, crust

must be destroyed at about the same rate as it is created. In fact, old crust is destroyed at

convergent boundaries. Old crust goes back into the mantle through the process of

subduction. How does this work? Continents are carried along the moving plates. Some

plates collide and break apart. These movements cause earthquakes and volcanic activity.

6 Here is where ocean trenches become important. Ocean trenches are also called submarine

valleys. They are the deepest parts of the ocean. Scientists must use special submarines to

explore the trenches. The water pressure is very high at these extreme depths. The

pressure can be equal to a car sitting on top of one square centimeter. The Marianas Trench

in the western Pacific Ocean reaches depths up to 11 km. Mount Everest is the tallest

mountain on Earth. Mount Everest could fit into the trench with 2 km to spare! These

trenches form where two tectonic plates come together. This is usually a continental plate

and an oceanic plate. The oceanic plate is denser. It gets pushed under the continental

plate. The oceanic plate goes back into the mantle and melts. This process often creates

earthquakes or hot spots that cause volcanoes. A perfect example of this is an area known

as the Pacific Ring of Fire. This large area forms a horseshoe shape around the Pacific

Ocean. It runs along the eastern coasts of Indonesia and Japan, north to Russia. Then it

extends to the west coast of North America, all the way to South America. It has the largest

number of active volcanoes and destructive earthquakes on the planet. Most of this activity

is due to subduction of the seafloor under tectonic plates at the continents’ edges.

7 The basics of the theory have been worked out over the last century. Research is still

discovering new aspects. Two large earthquakes were recorded in the Indian Ocean in

2012. These earthquakes suggest that the Australian and Indian plates are separating. The

actual separation will probably take several million years. Large earthquakes, however,

might become more common. Geologists have studied earthquake waves passing through

the crust near the California coast. Data show that a chunk of an ocean plate is still stuck to

the bottom of the continental plate. Subduction may therefore not always be smooth.

Research also shows that Earth may not be the only planet with plate tectonics. A large

canyon system on Mars seems to have fault lines. Fault lines often mark plate boundaries.

Several long lines of volcanoes suggest that a tectonic plate moved slowly over a hot spot.


Earth and Space

2

2 Which of the following correctly defines a divergent boundary?

A A small part of Earth’s mantle

B A location of high volcanic activity

C A location where tectonic plates move apart

D A section of crust that moves as a unit

1 Which of the following pieces of evidence does not explain how mid-ocean ridges are

formed?

A The rocks closer to the ridge are younger than those farther away.

B Mid-ocean ridges are found on the bottom of most oceans.

C The magnetic orientation of rocks is symmetrical on either side of mid-ocean

ridges.

D Pictures of ridges show evidence of lava flows.


Earth and Space

3

3 Which of the following is LEAST NECESSARY for plate tectonics?

A A solid core inside the planet.

B A semisolid mantle.

C Convection currents in the mantle.

D A crust divided into plates.

4 Which of the following statements regarding a convergent plate boundary between

continental crust and oceanic crust is not true?

A Earthquakes are common at the boundary.

B Mountains are formed.

C Hot spots that may create volcanoes are formed.

D Oceanic crust changes into continents.


Earth and Space

4

5 Subduction of ocean crust happens–

A at a mid-oceanic ridge.

B far from tectonic plate boundaries.

C inside volcanoes of the Ring of Fire.

D in deep ocean trenches.

6 What evidence suggests that the Australian and Indian plates are separating?

A The formation of a new oceanic ridge

B Recent large magnitude earthquakes

C The way earthquake waves travel through the area

D The presence of a string of volcanoes

5


Earth and Space

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